ROTORCRAFT FLYINGHANDBOOK

2000

U.S. DEPARTMENT OF TRANSPORTATIONFEDERAL AVIATION ADMINISTRATION

Flight Standards Service

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PREFACEThe Rotorcraft Flying Handbook is designed as a technical manual for applicants who are preparing for their pri-vate, commercial, or flight instructor pilot certificates with a helicopter or gyroplane class rating. Certificated flightinstructors may find this handbook a valuable training aid, since detailed coverage of aerodynamics, flight controls,systems, performance, flight maneuvers, emergencies, and aeronautical decision making is included. Topics, suchas weather, navigation, radio navigation and communications, use of flight information publications, and regula-tions are available in other Federal Aviation Administration (FAA) publications.

This handbook conforms to pilot training and certification concepts established by the FAA. There are differentways of teaching, as well as performing flight procedures and maneuvers, and many variations in the explanationsof aerodynamic theories and principles. This handbook adopts a selective method and concept to flying helicoptersand gyroplanes. The discussion and explanations reflect the most commonly used practices and principles.Occasionally, the word “must” or similar language is used where the desired action is deemed critical. The use ofsuch language is not intended to add to, interpret, or relieve a duty imposed by Title 14 of the Code of FederalRegulations (14 CFR). This handbook is divided into two parts. The first part, chapters 1 through 14, covers helicopters, and the second part, chapters 15 through 22, covers gyroplanes. The glossary and index apply to both parts.

It is essential for persons using this handbook to also become familiar with and apply the pertinent parts of 14 CFRand the Aeronautical Information Manual (AIM). Performance standards for demonstrating competence requiredfor pilot certification are prescribed in the appropriate rotorcraft practical test standard.

This handbook supersedes Advisory Circular (AC) 61-13B, Basic Helicopter Handbook, dated 1978. In addition,all or part of the information contained in the following advisory circulars are included in this handbook: AC 90-87, Helicopter Dynamic Rollover; AC 90-95, Unanticipated Right Yaw in Helicopters; AC 91-32B, Safety in andaround Helicopters; and AC 91-42D, Hazards of Rotating Propeller and Helicopter Rotor Blades.

This publication may be purchased from the Superintendent of Documents, U.S. Government Printing Office(GPO), Washington, DC 20402-9325, or from U.S. Government Bookstores located in major cities throughout theUnited States.

The current Flight Standards Service airman training and testing material and subject matter knowledge codes for all airman certificates and ratings can be obtained from the Flight Standards Services web site at http://av-info.faa.gov.

Comments regarding this handbook should be sent to U.S. Department of Transportation, Federal AviationAdministration, Airman Testing Standards Branch, AFS-630, P.O. Box 25082, Oklahoma City, OK 73125.

AC 00-2, Advisory Circular Checklist, transmits the current status of FAA advisory circulars and other flight infor-mation publications. This checklist is free of charge and may be obtained by sending a request to U.S. Departmentof Transportation, Subsequent Distribution Office, SVC-121.23, Ardmore East Business Center, 3341 Q 75thAvenue, Landover, MD 20785.

AC00-2 also is available on the Internet at http://www.faa.gov/abc/ac-chklst/actoc.htm.

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Chapter 4—Helicopter Flight ControlsCollective Pitch Control ..........................................4-1Throttle Control.......................................................4-1Collective Pitch / Throttle Coordination .................4-2Correlator / Governor ..............................................4-2Cyclic Pitch Control ................................................4-2Antitorque Pedals ....................................................4-3

Heading Control..................................................4-3

Chapter 5—Helicopter SystemsEngines ....................................................................5-1

Reciprocating Engine..........................................5-1Turbine Engine....................................................5-1

Compressor.....................................................5-2Combustion Chamber.....................................5-2Turbine ...........................................................5-2

Transmission System...............................................5-3Main Rotor Transmission ...................................5-3Tail Rotor Drive System.....................................5-3Clutch..................................................................5-4

Centrifugal Clutch..........................................5-4Belt Drive Clutch ...........................................5-4Freewheeling Unit ..........................................5-4

Main Rotor System .................................................5-4Fully Articulated Rotor System ..........................5-4Semirigid Rotor System......................................5-5Rigid Rotor System ............................................5-5Combination Rotor Systems...............................5-5Swash Plate Assembly ........................................5-5

Fuel Systems ...........................................................5-6Fuel Supply System ............................................5-6Engine Fuel Control System...............................5-6

Reciprocating Engines ...................................5-7Carburetor ..................................................5-7Carburetor Ice ............................................5-7Fuel Injection.............................................5-8

Turbine Engines .............................................5-8Electrical Systems ...................................................5-8Hydraulics ...............................................................5-9Stability Augmentations Systems..........................5-10Autopilot................................................................5-10Environmental Systems.........................................5-10Anti-Icing Systems ................................................5-11

Chapter 6—Rotorcraft Flight Manual (Helicopter)Preliminary Pages....................................................6-1General Information ................................................6-1Operating Limitations .............................................6-1

Airspeed Limitation ............................................6-1Altitude Limitations............................................6-2Rotor Limitations................................................6-2

HELICOPTER

Chapter 1—Introduction to the HelicopterThe Main Rotor System ..........................................1-1

Fully Articulated Rotor System ..........................1-1Semirigid Rotor System......................................1-2Rigid Rotor System ............................................1-2

Antitorque Systems .................................................1-2Tail Rotor ............................................................1-2Fenestron.............................................................1-2NOTAR®............................................................1-2

Landing Gear...........................................................1-2Powerplant...............................................................1-3Flight Controls.........................................................1-3

Chapter 2—General AerodynamicsAirfoil ......................................................................2-1

Relative Wind .....................................................2-2Blade Pitch Angle ...............................................2-2Angle of Attack...................................................2-2

Lift ...........................................................................2-3Magnus Effect.....................................................2-3Bernoulli’s Principle ...........................................2-3Newton’s Third Law of Motion..........................2-4

Weight......................................................................2-4Thrust.......................................................................2-5Drag .........................................................................2-5

Profile Drag ........................................................2-5Induced Drag ......................................................2-5Parasite Drag.......................................................2-6Total Drag ...........................................................2-6

Chapter 3—Aerodynamics of FlightPowered Flight ........................................................3-1Hovering Flight .......................................................3-1

Translating Tendency or Drift.............................3-1Pendular Action ..................................................3-2Coning.................................................................3-2Coriolis Effect (Law of Conservation of Angular Momentum) ..........................................3-2Ground Effect .....................................................3-3Gyroscopic Precession........................................3-4

Vertical Flight ..........................................................3-4Forward Flight.........................................................3-5

Translational Lift ................................................3-5Induced Flow ......................................................3-6Transverse Flow Effect .......................................3-6Dissymmetry of Lift ...........................................3-6

Sideward Flight .......................................................3-8Rearward Flight.......................................................3-8Turning Flight..........................................................3-8Autorotation.............................................................3-8

Autorotation (Vertical Flight) .............................3-9Autorotation (Forward Flight) ..........................3-11

CONTENTS

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Powerplant Limitations.......................................6-2Weight and Loading Distribution .......................6-2Flight Limitations ...............................................6-3Placards ...............................................................6-3

Emergency Procedures ............................................6-3Normal Procedures ..................................................6-3Performance.............................................................6-3Weight and Balance.................................................6-4Aircraft and Systems Description ...........................6-4Handling, Servicing, and Maintenance ...................6-4Supplements ............................................................6-4Safety and Operational Tips ....................................6-4

Chapter 7—Weight and BalanceWeight......................................................................7-1

Basic Empty Weight ...........................................7-1Useful Load ........................................................7-1Payload................................................................7-1Gross Weight.......................................................7-1Maximum Gross Weight .....................................7-1Weight Limitations .............................................7-1Determining Empty Weight ................................7-1

Balance ....................................................................7-2Center of Gravity ................................................7-2

CG Forward of Forward Limit.......................7-2CG Aft of Aft Limit .......................................7-2

Lateral Balance ...................................................7-3Weight and Balance Calculations............................7-3

Reference Datum ................................................7-3Arm .....................................................................7-4Moment ...............................................................7-4Center of Gravity Computation ..........................7-4

Weight and Balance Methods..................................7-4Computational Method .......................................7-4Loading Chart Method........................................7-5

Sample Problem 1 ..........................................7-5Sample Problem 2 ..........................................7-5Sample Problem 3 ..........................................7-6

Combination Method ..........................................7-6Calculating Lateral CG.......................................7-7

Chapter 8—PerformanceFactors Affecting Performance................................8-1

Density Altitude ..................................................8-1Atmospheric Pressure .........................................8-1Altitude ...............................................................8-2Temperature ........................................................8-2Moisture (Humidity) ...........................................8-2High and Low Density Altitude Conditions .......8-2Weight .................................................................8-2Winds ..................................................................8-2

Performance Charts .................................................8-3Hovering Performance........................................8-3

Sample Problem 1 ..........................................8-4Sample Problem 2 ..........................................8-4

Takeoff Performance...........................................8-5Sample Problem 3 ..........................................8-5

Climb Performance.............................................8-5Sample Problem 4 ..........................................8-6

Chapter 9—Basic Flight ManeuversPreflight ...................................................................9-1

Minimum Equipment Lists (MELS) andOperations With Inoperative Equipment ............9-1

Engine Start and Rotor Engagement.......................9-2Rotor Safety Considerations ...............................9-2Safety In and Around Helicopters ......................9-3

Ramp Attendants and Aircraft Servicing Personnel........................................9-3Aircraft Servicing...........................................9-3External-Load Riggers ...................................9-3Pilot at the Flight Controls.............................9-3External-Load Hookup Personnel ..................9-3Passengers ......................................................9-4

Vertical Takeoff to a Hover .....................................9-5Technique............................................................9-5Common Errors ..................................................9-5

Hovering..................................................................9-5Technique............................................................9-5Common Errors ..................................................9-5

Hovering Turn .........................................................9-6Technique............................................................9-6Common Errors ..................................................9-7

Hovering—Forward Flight......................................9-7Technique............................................................9-7Common Errors ..................................................9-7

Hovering—Sideward Flight ....................................9-7Technique............................................................9-7Common Errors ..................................................9-8

Hovering—Rearward Flight....................................9-8Technique............................................................9-8Common Errors ..................................................9-8

Taxiing.....................................................................9-8Hover Taxi ..........................................................9-9Air Taxi ...............................................................9-9

Technique .......................................................9-9Common Errors ..............................................9-9

Surface Taxi ........................................................9-9Technique .......................................................9-9Common Errors ............................................9-10

Normal Takeoff From a Hover..............................9-10Technique..........................................................9-10Common Errors ................................................9-10

Normal Takeoff From the Surface.........................9-11Technique ..........................................................9-11Common Errors.................................................9-11Crosswind ConsiderationsDuring Takeoffs ................................................9-11

Straight-and-Level Flight ......................................9-12

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Technique..........................................................9-12Common Errors ................................................9-12

Turns......................................................................9-12Technique..........................................................9-12Slips ..................................................................9-13Skids..................................................................9-13Common Errors ................................................9-13

Normal Climb........................................................9-13Technique..........................................................9-13Common Errors ................................................9-14

Normal Descent.....................................................9-14Technique..........................................................9-14Common Errors ................................................9-14

Ground Reference Maneuvers...............................9-14Rectangular Course...........................................9-14S-Turns..............................................................9-16Turns Around a Point........................................9-17Common Errors During Ground Reference Maneuvers .......................................9-18

Traffic Patterns ......................................................9-18Approaches ............................................................9-19

Normal Approach to a Hover ...........................9-19Technique .....................................................9-19Common Errors ............................................9-19

Normal Approach to the Surface ......................9-20Technique .....................................................9-20Common Errors ............................................9-20

Crosswind During Approaches .........................9-20Go-Around.............................................................9-20After Landing and Securing ..................................9-20Noise Abatement Procedures ................................9-20

Chapter 10—Advanced ManeuversReconnaissance Procedures...................................10-1

High Reconnaissance........................................10-1Low Reconnaissance ........................................10-1Ground Reconnaissance....................................10-1

Maximum Performance Takeoff ...........................10-2Technique..........................................................10-2Common Errors ................................................10-2

Running/Rolling Takeoff.......................................10-2Technique..........................................................10-3Common Errors ................................................10-3

Rapid Deceleration (Quick Stop) ..........................10-3Technique..........................................................10-3Common Errors ................................................10-4

Steep Approach to a Hover ...................................10-4Technique..........................................................10-4Common Errors ................................................10-5

Shallow Approach and Running/Roll-On Landing..................................................................10-5

Technique..........................................................10-5Common Errors ................................................10-5

Slope Operations ...................................................10-6Slope Landing...................................................10-6

Technique.....................................................10-6Common Errors............................................10-6

Slope Takeoff ....................................................10-6Technique.....................................................10-7Common Errors............................................10-7

Confined Area Operations.....................................10-7Approach...........................................................10-7Takeoff ..............................................................10-8Common Errors ................................................10-8

Pinnacle and Ridgeline Operations .......................10-8Approach and Landing .....................................10-8Takeoff ..............................................................10-9Common Errors ................................................10-9

Chapter 11—Helicopter EmergenciesAutorotation...........................................................11-1

Straight-in Autorotation ....................................11-2Technique .....................................................11-2Common Errors............................................11-3

Power Recovery From Practice Autorotation ......................................................11-3

Technique .....................................................11-3Common Errors............................................11-3

Autorotation With Turns ...................................11-3Technique .....................................................11-3

Power Failure in a Hover..................................11-4Technique .....................................................11-4Common Errors............................................11-4

Height/Velocity Diagram.......................................11-4The Effect of Weight Versus Density Altitude ................................................11-5

Vortex Ring State (Settling With Power) ..............11-5Retreating Blade Stall............................................11-6Ground Resonance.................................................11-7Dynamic Rollover .................................................11-7

Critical Conditions ............................................11-8Cyclic Trim .......................................................11-8Normal Takeoffs and Landings.........................11-8Slope Takeoffs and Landings............................11-8Use of Collective ..............................................11-9Precautions ........................................................11-9

Low G Conditions and Mast Bumping ...............11-10Low Rotor RPM and Blade Stall ........................11-10Recovery From Low Rotor RPM........................11-10Systems Malfunctions..........................................11-11

Antitorque System Failure ..............................11-11Landing—Stuck Left Pedal........................11-11Landing—Stuck Neutral or Right Pedal .................................................11-12

Unanticipated Yaw / Loss of Tail RotorEffectiveness (LTE) ........................................11-12Main Rotor Disc Interference (285-315°) .......................................................11-12Weathercock Stability(120-240°) .......................................................11-13

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Tail Rotor Vortex Ring State (210-330°) .......................................................11-13

LTE at Altitude...........................................11-13Reducing the Onset of LTE .......................11-13Recovery Technique...................................11-14

Main Drive Shaft Failure ................................11-14Hydraulic Failures...........................................11-14Governor Failure.............................................11-14Abnormal Vibrations.......................................11-14

Low Frequency Vibrations.........................11-15Medium and High Frequency Vibrations ...................................................11-15Tracking and Balance ................................11-15

Flight Diversion...................................................11-15Lost Procedures ...................................................11-16Emergency Equipment and Survival Gear ..........11-16

Chapter 12—Attitude Instrument FlyingFlight Instruments .................................................12-1

Pitot-Static Instruments ....................................12-1Airspeed Indicator........................................12-1Instrument Check.........................................12-1Altimeter ......................................................12-2

Instrument Check.....................................12-2Vertical Speed Indicator....................................12-2

Instrument Check.........................................12-2System Errors...............................................12-2

Gyroscopic Instruments ....................................12-3Attitude Indicator.........................................12-3Heading Indicator ........................................12-3Turn Indicators.............................................12-4Instrument Check.........................................12-4

Magnetic Compass............................................12-4Compass Errors............................................12-4Magnetic Variation.......................................12-4

Compass Deviation..................................12-5Magnetic Dip ...........................................12-5Instrument Check.....................................12-5

Instrument Flight ...................................................12-5Instrument Cross-Check ...................................12-5Instrument Interpretation ..................................12-6Aircraft Control ................................................12-7Straight-and-Level Flight..................................12-7

Pitch Control ................................................12-7Attitude Indicator.....................................12-8Altimeter ..................................................12-8Vertical Speed Indicator ..........................12-8Airspeed Indicator ...................................12-9

Bank Control................................................12-9Attitude Indicator.....................................12-9Heading Indicator ..................................12-10Turn Indicator ........................................12-10

Common Errors During Straight-and-Level Flight ...........................12-10

Power Control During Straight-and-Level Flight ...........................12-11Common Errors During Airspeed Changes.......................................12-11

Straight Climbs (Constant Airspeed and Constant Rate)..........................................12-11

Entry...........................................................12-12Leveloff......................................................12-14

Straight Descents (Constant Airspeed and Constant Rate) ................................................12-14

Entry...........................................................12-14Leveloff......................................................12-15Common Errors During Straight Climbs and Descents ....................12-15

Turns ...............................................................12-15Turns to a Predetermined Heading ............12-16Timed Turns ...............................................12-16

Change of Airspeed in Turns .................12-1630° Bank Turn............................................12-17Climbing and Descending Turns ...............12-17Compass Turns...........................................12-17Common Errors During Turns...................12-18

Unusual Attitudes............................................12-18Common Errors During Unusual Attitude Recoveries ....................................12-18

Emergencies ........................................................12-18Autorotations ..................................................12-19

Common Errors During Autorotations..............................................12-19

Servo Failure...................................................12-19Instrument Takeoff ..............................................12-19

Common Errors During Instrument Takeoffs ........................................12-20

Chapter 13—Night OperationsNight Flight Physiology ........................................13-1

Vision in Flight .................................................13-1The Eye.............................................................13-1Cones ................................................................13-1Rods ..................................................................13-2Night Vision......................................................13-2Night Scanning .................................................13-2Aircraft Lighting ...............................................13-3Visual Illusions .................................................13-3

Autokinesis ..................................................13-3Night Myopia...............................................13-3False Horizon...............................................13-3Landing Illusions .........................................13-4

Night Flight ...........................................................13-4Preflight ............................................................13-4Engine Starting and Rotor Engagement ...........13-4Taxi Technique..................................................13-4Takeoff ..............................................................13-4En route Procedures..........................................13-5

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Collision Avoidance at Night............................13-5Approach and Landing .....................................13-5

Chapter 14—Aeronautical Decision MakingOrigins of ADM Training......................................14-2The Decision-Making Process ..............................14-3

Defining the Problem........................................14-3Choosing a Course of Action............................14-3Implementing the Decision and Evaluating the Outcome ...................................14-3

Risk Management..................................................14-4Assessing Risk ..................................................14-4

Factors Affecting Decision Making ......................14-5Pilot Self-Assessment .......................................14-5Recognizing Hazardous Attitudes ....................14-5Stress management ...........................................14-6Use of Resources ..............................................14-6

Internal Resources ........................................14-7External Resources.......................................14-7

Workload Management.....................................14-7Situational Awareness .......................................14-8

Obstacles to Maintaining Situational Awareness ..................................14-8Operational Pitfalls.......................................14-8

GYROPLANEChapter 15—Introduction to the GyroplaneTypes of Gyroplanes..............................................15-1Components...........................................................15-2

Airframe............................................................15-2Powerplant ........................................................15-2Rotor System ....................................................15-2Tail Surfaces .....................................................15-2Landing Gear ....................................................15-3Wings ................................................................15-3

Chapter 16—Aerodynamics of the GyroplaneAutorotation...........................................................16-1

Vertical Autorotation.........................................16-1Rotor Disc Regions...........................................16-2Autorotation in Forward Flight ........................16-2

Reverse Flow................................................16-3Retreating Blade Stall ..................................16-3

Rotor Force............................................................16-3Rotor Lift ..........................................................16-4Rotor Drag ........................................................16-4

Thrust.....................................................................16-4Stability .................................................................16-5

Horizontal Stabilizer .........................................16-5Fuselage Drag (Center of Pressure)..................16-5Pitch Inertia.......................................................16-5

Propeller Thrust Line........................................16-5Rotor Force .......................................................16-6Trimmed Condition...........................................16-6

Chapter 17—Gyroplane Flight ControlsCyclic Control .......................................................17-1Throttle ..................................................................17-1Rudder ...................................................................17-2Horizontal Tail Surfaces........................................17-2Collective Control .................................................17-2

Chapter 18—Gyroplane SystemsPropulsion Systems ...............................................18-1Rotor Systems .......................................................18-1

Semirigid Rotor System....................................18-1Fully Articulated Rotor System ........................18-1

Prerotator ...............................................................18-2Mechanical Prerotator.......................................18-2Hydraulic Prerotator .........................................18-2Electric Prerotator .............................................18-3Tip Jets ..............................................................18-3

Instrumentation......................................................18-3Engine Instruments ...........................................18-3Rotor Tachometer .............................................18-3Slip/Skid Indicator ............................................18-4Airspeed Indicator ............................................18-4Altimeter ...........................................................18-4IFR Flight Instrumentation ...............................18-4

Ground Handling...................................................18-4

Chapter 19—Rotorcraft Flight Manual(Gyroplane)

Using the Flight Manual........................................19-1Weight and Balance Section .............................19-1

Sample Problem ...........................................19-1Performance Section .........................................19-2

Sample Problem ...........................................19-2Height/Velocity Diagram .............................19-3

Emergency Section ...........................................19-3Hang Test...............................................................19-4

Chapter 20—Flight OperationsPreflight .................................................................20-1

Cockpit Management........................................20-1Engine Starting ......................................................20-1Taxiing...................................................................20-1

Blade Flap.........................................................20-1Before Takeoff.......................................................20-2

Prerotation.........................................................20-2Takeoff...................................................................20-3

Normal Takeoff .................................................20-3Crosswind Takeoff ............................................20-4Common Errors for Normal and Crosswind Takeoffs ..........................................20-4Short-Field Takeoff ...........................................20-4

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Common Errors ............................................20-4High-Altitude Takeoff ..................................20-4

Soft-Field Takeoff .............................................20-5Common Errors ............................................20-5Jump Takeoff ................................................20-5

Basic Flight Maneuvers.........................................20-6Straight-and-Level Flight..................................20-6Climbs...............................................................20-6Descents ............................................................20-7Turns .................................................................20-7

Slips..............................................................20-7Skids .............................................................20-7

Common Errors During Basic Flight Maneuvers ..............................................20-8Steep Turns .......................................................20-8

Common Errors ............................................20-8Ground Reference Maneuvers...............................20-8

Rectangular Course...........................................20-8S-Turns............................................................20-10Turns Around a Point ......................................20-11Common Errors During Ground Reference Maneuvers ........................20-11

Flight at Slow Airspeeds .....................................20-12Common Errors ..............................................20-12

High Rate of Descent ..........................................20-12Common Errors ..............................................20-13

Landings ..............................................................20-13Normal Landing..............................................20-13Short-Field Landing........................................20-13Soft-Field Landing..........................................20-14Crosswind Landing.........................................20-14

High-Altitude Landing....................................20-14Common Errors During Landing....................20-15

Go-Around...........................................................20-15Common Errors ..............................................20-15

After Landing and Securing ................................20-15

Chapter 21—Gyroplane EmergenciesAborted Takeoff.....................................................21-1

Accelerate/Stop Distance..................................21-1Lift-off at Low Airspeed andHigh Angle of Attack ............................................21-1

Common Errors ................................................21-2Pilot-Induced Oscillation (PIO) ............................21-2Buntover (Power Pushover) ..................................21-3Ground Resonance ................................................21-3Emergency Approach and Landing.......................21-3Emergency Equipment and Survival Gear............21-4

Chapter 22—Gyroplane Aeronautical DecisionMaking

Impulsivity.............................................................22-1Invulnerability .......................................................22-1Macho....................................................................22-2Resignation............................................................22-2Anti-Authority .......................................................22-3

Glossary.................................................................G-1

Index........................................................................I-1

1-1

Helicopters come in many sizes and shapes, but mostshare the same major components. These componentsinclude a cabin where the payload and crew are car-ried; an airframe, which houses the various compo-nents, or where components are attached; a powerplantor engine; and a transmission, which, among otherthings, takes the power from the engine and transmits itto the main rotor, which provides the aerodynamicforces that make the helicopter fly. Then, to keep thehelicopter from turning due to torque, there must besome type of antitorque system. Finally there is thelanding gear, which could be skids, wheels, skis, orfloats. This chapter is an introduction to these compo-nents. [Figure 1-1]

THE MAIN ROTOR SYSTEMThe rotor system found on helicopters can consist of asingle main rotor or dual rotors. With most dual rotors,the rotors turn in opposite directions so the torque fromone rotor is opposed by the torque of the other. Thiscancels the turning tendencies. [Figure 1-2]

In general, a rotor system can be classified as eitherfully articulated, semirigid, or rigid. There are varia-tions and combinations of these systems, which will bediscussed in greater detail in Chapter 5—HelicopterSystems.

FULLY ARTICULATED ROTOR SYSTEMA fully articulated rotor system usually consists ofthree or more rotor blades. The blades are allowed toflap, feather, and lead or lag independently of eachother. Each rotor blade is attached to the rotor hub by ahorizontal hinge, called the flapping hinge, which per-mits the blades to flap up and down. Each blade canmove up and down independently of the others. Theflapping hinge may be located at varying distancesfrom the rotor hub, and there may be more than one.The position is chosen by each manufacturer, primarilywith regard to stability and control.

Payload—The term used for pas-sengers, baggage, and cargo.

Torque—In helicopters with a sin-gle, main rotor system, the ten-dency of the helicopter to turn inthe opposite direction of the mainrotor rotation.

Blade Flap—The upward ordownward movement of the rotorblades during rotation.

Blade Feather or Feathering—Therotation of the blade around thespanwise (pitch change) axis.

Blade Lead or Lag—The fore andaft movement of the blade in theplane of rotation. It is sometimescalled hunting or dragging.

Landing Gear

Tail Rotor System

Main Rotor System

Cabin

Airframe Transmission

Powerplant

Figure 1-2. Helicopters can have a single main rotor or a dual rotor system.

Figure 1-1. The major components of a helicopter are thecabin, airframe, landing gear, powerplant, transmission, mainrotor system, and tail rotor system.

1-2

Each rotor blade is also attached to the hub by a verti-cal hinge, called a drag or lag hinge, that permits eachblade, independently of the others, to move back andforth in the plane of the rotor disc. Dampers are nor-mally incorporated in the design of this type of rotorsystem to prevent excessive motion about the draghinge. The purpose of the drag hinge and dampers is toabsorb the acceleration and deceleration of the rotorblades.

The blades of a fully articulated rotor can also be feath-ered, or rotated about their spanwise axis. To put itmore simply, feathering means the changing of thepitch angle of the rotor blades.

SEMIRIGID ROTOR SYSTEMA semirigid rotor system allows for two differentmovements, flapping and feathering. This system isnormally comprised of two blades, which are rigidlyattached to the rotor hub. The hub is then attached tothe rotor mast by a trunnion bearing or teetering hinge.This allows the blades to see-saw or flap together. Asone blade flaps down, the other flaps up. Feathering isaccomplished by the feathering hinge, which changesthe pitch angle of the blade.

RIGID ROTOR SYSTEMThe rigid rotor system is mechanically simple, butstructurally complex because operating loads must beabsorbed in bending rather than through hinges. In thissystem, the blades cannot flap or lead and lag, but theycan be feathered.

ANTITORQUE SYSTEMSTAIL ROTORMost helicopters with a single, main rotor systemrequire a separate rotor to overcome torque. This isaccomplished through a variable pitch, antitorque rotoror tail rotor. [Figure 1-3]. You will need to vary the

thrust of the antitorque system to maintain directionalcontrol whenever the main rotor torque changes, or tomake heading changes while hovering.

FENESTRONAnother form of antitorque rotor is the fenestron or“fan-in-tail” design. This system uses a series of rotat-ing blades shrouded within a vertical tail. Because theblades are located within a circular duct, they are lesslikely to come into contact with people or objects.[Figure 1-4]

NOTAR®The NOTAR® system is an alternative to the antitorquerotor. The system uses low-pressure air that is forcedinto the tailboom by a fan mounted within the helicop-ter. The air is then fed through horizontal slots, locatedon the right side of the tailboom, and to a controllablerotating nozzle to provide antitorque and directionalcontrol. The low-pressure air coming from the horizon-tal slots, in conjunction with the downwash from themain rotor, creates a phenomenon called “CoandaEffect,” which produces a lifting force on the right sideof the tailboom. [Figure 1-5]

LANDING GEARThe most common landing gear is a skid type gear,which is suitable for landing on various types of sur-faces. Some types of skid gear are equipped withdampers so touchdown shocks or jolts are not transmit-ted to the main rotor system. Other types absorb theshocks by the bending of the skid attachment arms.Landing skids may be fitted with replaceable heavy-duty skid shoes to protect them from excessive wearand tear.

Helicopters can also be equipped with floats for wateroperations, or skis for landing on snow or soft terrain.Wheels are another type of landing gear. They may bein a tricycle or four point configuration. Normally, the

Tail Rotor Thrust to Compensate for Torque

Torque

Torque

Blade Rotation

F

Figure 1-3. The antitorque rotor produces thrust to opposetorque and helps prevent the helicopter from turning in theopposite direction of the main rotor.

Figure 1-4. Compared to an unprotected tail rotor, the fene-stron antitorque system provides an improved margin ofsafety during ground operations.

1-3

nose or tail gear is free to swivel as the helicopter istaxied on the ground.

POWERPLANTA typical small helicopter has a reciprocating engine,which is mounted on the airframe. The engine can bemounted horizontally or vertically with the transmis-sion supplying the power to the vertical main rotorshaft. [Figure 1-6]

Another engine type is the gas turbine. This engine isused in most medium to heavy lift helicopters due to its

large horsepower output. The engine drives the maintransmission, which then transfers power directly to themain rotor system, as well as the tail rotor.

FLIGHT CONTROLSWhen you begin flying a helicopter, you will use fourbasic flight controls. They are the cyclic pitch control;the collective pitch control; the throttle, which isusually a twist grip control located on the end of thecollective lever; and the antitorque pedals. The col-lective and cyclic controls the pitch of the main rotorblades. The function of these controls will be explainedin detail in Chapter 4—Flight Controls. [Figure 1-7]

Figure 1-5. While in a hover, Coanda Effect supplies approxi-mately two-thirds of the lift necessary to maintain directionalcontrol. The rest is created by directing the thrust from thecontrollable rotating nozzle.

Main Rotor Wake

Rotating Nozzle

Downwash

Air Jet

Lift

Air Intake

Main Rotor

Main Transmission

Antitorque Rotor

Engine

Figure 1-6. Typically, the engine drives the main rotor througha transmission and belt drive or centrifugal clutch system.The antitorque rotor is driven from the transmission.

Cyclic

Throttle

Collective

Antitorque Pedals

Figure 1-7. Location of flight controls.

1-4

2-1

There are four forces acting on a helicopter in flight.They are lift, weight, thrust, and drag. [Figure 2-1] Liftis the upward force created by the effect of airflow as itpasses around an airfoil. Weight opposes lift and iscaused by the downward pull of gravity. Thrust is theforce that propels the helicopter through the air.Opposing lift and thrust is drag, which is the retardingforce created by development of lift and the movementof an object through the air.

AIRFOILBefore beginning the discussion of lift, you need to beaware of certain aerodynamic terms that describe anairfoil and the interaction of the airflow around it.

An airfoil is any surface, such as an airplane wing or ahelicopter rotor blade, which provides aerodynamicforce when it interacts with a moving stream of air.Although there are many different rotor blade airfoildesigns, in most helicopter flight conditions, all airfoilsperform in the same manner.

Engineers of the first helicopters designed relativelythick airfoils for their structural characteristics.Because the rotor blades were very long and slender, itwas necessary to incorporate more structural rigidityinto them. This prevented excessive blade droop whenthe rotor system was idle, and minimized blade twist-ing while in flight. The airfoils were also designed tobe symmetrical, which means they had the same cam-ber (curvature) on both the upper and lower surfaces.

Symmetrical blades are very stable, which helps keepblade twisting and flight control loads to a minimum.[Figure 2-2] This stability is achieved by keeping thecenter of pressure virtually unchanged as the angle ofattack changes. Center of pressure is the imaginarypoint on the chord line where the resultant of all aero-dynamic forces are considered to be concentrated.

Today, designers use thinner airfoils and obtain therequired rigidity by using composite materials. In addi-tion, airfoils are asymmetrical in design, meaning theupper and lower surface do not have the same camber.Normally these airfoils would not be as stable, but thiscan be corrected by bending the trailing edge to producethe same characteristics as symmetrical airfoils. This iscalled “reflexing.” Using this type of rotor blade allowsthe rotor system to operate at higher forward speeds.

One of the reasons an asymmetrical rotor blade is notas stable is that the center of pressure changes withchanges in angle of attack. When the center of pressurelifting force is behind the pivot point on a rotor blade, ittends to cause the rotor disc to pitch up. As the angle ofattack increases, the center of pressure moves forward.If it moves ahead of the pivot point, the pitch of therotor disc decreases. Since the angle of attack of therotor blades is constantly changing during each cycleof rotation, the blades tend to flap, feather, lead, andlag to a greater degree.

When referring to an airfoil, the span is the distancefrom the rotor hub to the blade tip. Blade twist refers toa changing chord line from the blade root to the tip.

Figure 2-2. The upper and lower curvatures are the same on asymmetrical airfoil and vary on an asymmetrical airfoil.

Asymmetrical

Symmetrical

Lift

Weight

Drag

Thrust

Figure 2-1. Four forces acting on a helicopter in forward flight.

2-2

Twisting a rotor blade causes it to produce a more evenamount of lift along its span. This is necessary becauserotational velocity increases toward the blade tip. Theleading edge is the first part of the airfoil to meet theoncoming air. [Figure 2-3] The trailing edge is the aftportion where the airflow over the upper surface joinsthe airflow under the lower surface. The chord line isan imaginary straight line drawn from the leading tothe trailing edge. The camber is the curvature of the air-foil’s upper and lower surfaces. The relative wind is thewind moving past the airfoil. The direction of this windis relative to the attitude, or position, of the airfoil andis always parallel, equal, and opposite in direction tothe flight path of the airfoil. The angle of attack is theangle between the blade chord line and the direction ofthe relative wind.

RELATIVE WINDRelative wind is created by the motion of an airfoilthrough the air, by the motion of air past an airfoil, or bya combination of the two. Relative wind may beaffected by several factors, including the rotation of therotor blades, horizontal movement of the helicopter,flapping of the rotor blades, and wind speed and direction.

For a helicopter, the relative wind is the flow of air withrespect to the rotor blades. If the rotor is stopped, windblowing over the blades creates a relative wind. Whenthe helicopter is hovering in a no-wind condition, rela-tive wind is created by the motion of the rotor bladesthrough the air. If the helicopter is hovering in a wind,the relative wind is a combination of the wind and themotion of the rotor blades through the air. When thehelicopter is in forward flight, the relative wind is acombination of the rotation of the rotor blades and theforward speed of the helicopter.

BLADE PITCH ANGLEThe pitch angle of a rotor blade is the angle between itschord line and the reference plane containing the rotorhub. [Figure 2-4] You control the pitch angle of the bladeswith the flight controls. The collective pitch changes eachrotor blade an equal amount of pitch no matter where it islocated in the plane of rotation (rotor disc) and is used tochange rotor thrust. The cyclic pitch control changes thepitch of each blade as a function of where it is in the planeof rotation. This allows for trimming the helicopter inpitch and roll during forward flight and for maneuveringin all flight conditions.

ANGLE OF ATTACKWhen the angle of attack is increased, air flowing overthe airfoil is diverted over a greater distance, resultingin an increase of air velocity and more lift. As angle ofattack is increased further, it becomes more difficult forair to flow smoothly across the top of the airfoil. At thispoint the airflow begins to separate from the airfoil andenters a burbling or turbulent pattern. The turbulenceresults in a large increase in drag and loss of lift in thearea where it is taking place. Increasing the angle ofattack increases lift until the critical angle of attack isreached. Any increase in the angle of attack beyond thispoint produces a stall and a rapid decrease in lift.[Figure 2-5]

Angle of attack should not be confused with pitchangle. Pitch angle is determined by the direction of therelative wind. You can, however, change the angle ofattack by changing the pitch angle through the use ofthe flight controls. If the pitch angle is increased, theangle of attack is increased, if the pitch angle isreduced, the angle of attack is reduced. [Figure 2-6]

Axis-of-Rotation—The imaginaryline about which the rotor rotates.It is represented by a line drawnthrough the center of, and perpen-dicular to, the tip-path plane.

Tip-Path Plane—The imaginarycircular plane outlined by therotor blade tips as they make acycle of rotation.

Aircraft Pitch—When referencedto a helicopter, is the movement ofthe helicopter about its lateral, orside to side axis. Movement of thecyclic forward or aft causes thenose of the helicopter to move upor down.

Aircraft Roll—Is the movement ofthe helicopter about its longitudi-nal, or nose to tail axis. Movementof the cyclic right or left causes thehelicopter to tilt in that direction.

Figure 2-3. Aerodynamic terms of an airfoil.

Trailing Edge

Chord Line Angle ofAttack

FLIGHT PATHRELATIVE WIND

Upper Camber

Lower Camber

Leading Edge

Axis of Rotation

Reference PlanePitch Angle

Chord Line

Figure 2-4. Do not confuse the axis of rotation with the rotormast. The only time they coincide is when the tip-path planeis perpendicular to the rotor mast.

2-3

LIFTMAGNUS EFFECTThe explanation of lift can best be explained by lookingat a cylinder rotating in an airstream. The local velocitynear the cylinder is composed of the airstream velocityand the cylinder’s rotational velocity, which decreaseswith distance from the cylinder. On a cylinder, which isrotating in such a way that the top surface area is rotatingin the same direction as the airflow, the local velocity atthe surface is high on top and low on the bottom.

As shown in figure 2-7, at point “A,” a stagnation pointexists where the airstream line that impinges on the sur-face splits; some air goes over and some under. Anotherstagnation point exists at “B,” where the two airstreams rejoin and resume at identical velocities. We

now have upwash ahead of the rotating cylinder anddownwash at the rear.

The difference in surface velocity accounts for a differ-ence in pressure, with the pressure being lower on thetop than the bottom. This low pressure area producesan upward force known as the “Magnus Effect.” Thismechanically induced circulation illustrates the rela-tionship between circulation and lift.

An airfoil with a positive angle of attack develops aircirculation as its sharp trailing edge forces the rearstagnation point to be aft of the trailing edge, while thefront stagnation point is below the leading edge.[Figure 2-8]

BERNOULLI’S PRINCIPLEAir flowing over the top surface accelerates. The airfoilis now subjected to Bernoulli’s Principle or the “venturieffect.” As air velocity increases through the constrictedportion of a venturi tube, the pressure decreases.

Axis of Rotation

Reference Plane

Pitch Angle

Chord Line

Angle ofAttack

RELATIVE WIND

Figure 2-6. Angle of attack may be greater than, less than, orthe same as the pitch angle.

Figure 2-5. As the angle of attack is increased, the separationpoint starts near the trailing edge of the airfoil and pro-gresses forward. Finally, the airfoil loses its lift and a stallcondition occurs.

LIFT

STALL

8°

12-16° Figure 2-7. Magnus Effect is a lifting force produced when arotating cylinder produces a pressure differential. This is thesame effect that makes a baseball curve or a golf ball slice.

B A

Increased Local Velocity (Decreased pressure)

Decreased Local Velocity

Downwash Upwash

Figure 2-8. Air circulation around an airfoil occurs when thefront stagnation point is below the leading edge and the aftstagnation point is beyond the trailing edge.

Leading Edge Stagnation Point

Trailing Edge Stagnation Point

B

A

Steady-State Flight—A conditionwhen an aircraft is in straight-and-level, unaccelerated flight,and all forces are in balance.

2-4

ward. According to Newton’s Third Law of Motion,“for every action there is an equal and opposite reac-tion,” the air that is deflected downward also producesan upward (lifting) reaction.

Since air is much like water, the explanation for thissource of lift may be compared to the planing effect ofskis on water. The lift which supports the water skis(and the skier) is the force caused by the impact pres-sure and the deflection of water from the lower surfacesof the skis.

Under most flying conditions, the impact pressure andthe deflection of air from the lower surface of the rotorblade provides a comparatively small percentage of thetotal lift. The majority of lift is the result of decreasedpressure above the blade, rather than the increasedpressure below it.

WEIGHTNormally, weight is thought of as being a known, fixedvalue, such as the weight of the helicopter, fuel, andoccupants. To lift the helicopter off the ground verti-cally, the rotor system must generate enough lift toovercome or offset the total weight of the helicopterand its occupants. This is accomplished by increasingthe pitch angle of the main rotor blades.

The weight of the helicopter can also be influenced byaerodynamic loads. When you bank a helicopter whilemaintaining a constant altitude, the “G” load or loadfactor increases. Load factor is the ratio of the load sup-ported by the main rotor system to the actual weight ofthe helicopter and its contents. In steady-state flight,the helicopter has a load factor of one, which means themain rotor system is supporting the actual total weightof the helicopter. If you increase the bank angle to 60°,while still maintaining a constant altitude, the load fac-tor increases to two. In this case, the main rotor systemhas to support twice the weight of the helicopter and itscontents. [Figure 2-11]

Disc loading of a helicopter is the ratio of weight to thetotal main rotor disc area, and is determined by divid-ing the total helicopter weight by the rotor disc area,which is the area swept by the blades of a rotor. Discarea can be found by using the span of one rotor bladeas the radius of a circle and then determining the areathe blades encompass during a complete rotation. Asthe helicopter is maneuvered, disc loading changes.The higher the loading, the more power you need tomaintain rotor speed.

Leading Edge Stagnation Point

B

A

Compare the upper surface of an airfoil with the con-striction in a venturi tube that is narrower in the middlethan at the ends. [Figure 2-9]

The upper half of the venturi tube can be replaced bylayers of undisturbed air. Thus, as air flows over theupper surface of an airfoil, the camber of the airfoilcauses an increase in the speed of the airflow. Theincreased speed of airflow results in a decrease in pres-sure on the upper surface of the airfoil. At the sametime, air flows along the lower surface of the airfoil,building up pressure. The combination of decreasedpressure on the upper surface and increased pressureon the lower surface results in an upward force.[Figure 2-10]

As angle of attack is increased, the production of lift isincreased. More upwash is created ahead of the airfoilas the leading edge stagnation point moves under theleading edge, and more downwash is created aft of thetrailing edge. Total lift now being produced is perpen-dicular to relative wind. In summary, the production oflift is based upon the airfoil creating circulation in theairstream (Magnus Effect) and creating differentialpressure on the airfoil (Bernoulli’s Principle).

NEWTON’S THIRD LAW OF MOTIONAdditional lift is provided by the rotor blade’s lowersurface as air striking the underside is deflected down-

Figure 2-10. Lift is produced when there is decreased pres-sure above and increased pressure below an airfoil.

LiftDecreased Pressure

Increased Pressure

Increased Velocity Decreased Pressure

Figure 2-9. The upper surface of an airfoil is similar to theconstriction in a venturi tube.

2-5

DRAGThe force that resists the movement of a helicopterthrough the air and is produced when lift is developedis called drag. Drag always acts parallel to the relativewind. Total drag is composed of three types of drag:profile, induced, and parasite.

PROFILE DRAGProfile drag develops from the frictional resistance ofthe blades passing through the air. It does not changesignificantly with the airfoil’s angle of attack, butincreases moderately when airspeed increases. Profiledrag is composed of form drag and skin friction.

Form drag results from the turbulent wake caused bythe separation of airflow from the surface of a struc-ture. The amount of drag is related to both the size andshape of the structure that protrudes into the relativewind. [Figure 2-12]

Skin friction is caused by surface roughness. Eventhough the surface appears smooth, it may be quiterough when viewed under a microscope. A thin layer ofair clings to the rough surface and creates small eddiesthat contribute to drag.

INDUCED DRAGInduced drag is generated by the airflow circulationaround the rotor blade as it creates lift. The high-pres-sure area beneath the blade joins the low-pressure airabove the blade at the trailing edge and at the rotor tips.This causes a spiral, or vortex, which trails behind eachblade whenever lift is being produced. These vorticesdeflect the airstream downward in the vicinity of theblade, creating an increase in downwash. Therefore,the blade operates in an average relative wind that isinclined downward and rearward near the blade.Because the lift produced by the blade is perpendicular

Aircraft Yaw—The movement ofthe helicopter about its verticalaxis.

THRUSTThrust, like lift, is generated by the rotation of themain rotor system. In a helicopter, thrust can be for-ward, rearward, sideward, or vertical. The resultant oflift and thrust determines the direction of movement ofthe helicopter.

The solidity ratio is the ratio of the total rotor bladearea, which is the combined area of all the main rotorblades, to the total rotor disc area. This ratio provides ameans to measure the potential for a rotor system toprovide thrust.

The tail rotor also produces thrust. The amount ofthrust is variable through the use of the antitorque ped-als and is used to control the helicopter’s yaw.

Figure 2-11. The load factor diagram allows you to calculatethe amount of “G” loading exerted with various angle ofbank.

Load

Fact

or-

"G's

"

Bank Angle (in Degrees)0 10 20 30 40 50 60 70 80 90

9

8

7

6

5

4

3

2

1

0

Figure 2-12. It is easy to visualize the creation of form drag by examining the airflow around a flat plate. Streamlining decreasesform drag by reducing the airflow separation.

2-6

to the relative wind, the lift is inclined aft by the sameamount. The component of lift that is acting in a rear-ward direction is induced drag. [Figure 2-13]

As the air pressure differential increases with anincrease in angle of attack, stronger vortices form, andinduced drag increases. Since the blade’s angle ofattack is usually lower at higher airspeeds, and higherat low speeds, induced drag decreases as airspeedincreases and increases as airspeed decreases. Induceddrag is the major cause of drag at lower airspeeds.

PARASITE DRAGParasite drag is present any time the helicopter is movingthrough the air. This type of drag increases with airspeed.Nonlifting components of the helicopter, such as thecabin, rotor mast, tail, and landing gear, contribute to par-asite drag. Any loss of momentum by the airstream, dueto such things as openings for engine cooling, createsadditional parasite drag. Because of its rapid increase

with increasing airspeed, parasite drag is the major causeof drag at higher airspeeds. Parasite drag varies with thesquare of the velocity. Doubling the airspeed increasesthe parasite drag four times.

TOTAL DRAGTotal drag for a helicopter is the sum of all three dragforces. [Figure 2-14] As airspeed increases, parasitedrag increases, while induced drag decreases. Profiledrag remains relatively constant throughout the speedrange with some increase at higher airspeeds.Combining all drag forces results in a total drag curve.The low point on the total drag curve shows the air-speed at which drag is minimized. This is the pointwhere the lift-to-drag ratio is greatest and is referred toas L/Dmax. At this speed, the total lift capacity of thehelicopter, when compared to the total drag of the heli-copter, is most favorable. This is important in helicopterperformance.

Figure 2-14. The total drag curve represents the combinedforces of parasite, profile, and induced drag; and is plottedagainst airspeed.

0 25 50 75 100 125 150Speed

Dra

g

Parasite Drag Profile Drag

Induced Drag

Total Drag

Minimum Drag or L/D max

L/Dmax—The maximum ratiobetween total lift (L) and the totaldrag (D). This point provides thebest glide speed. Any deviationfrom best glide speed increasesdrag and reduces the distance youcan glide.

Induced Drag

Figure 2-13. The formation of induced drag is associated withthe downward deflection of the airstream near the rotorblade.

3-1

Once a helicopter leaves the ground, it is acted upon bythe four aerodynamic forces. In this chapter, we willexamine these forces as they relate to flight maneuvers.

POWERED FLIGHTIn powered flight (hovering, vertical, forward, side-ward, or rearward), the total lift and thrust forces of arotor are perpendicular to the tip-path plane or plane ofrotation of the rotor.

HOVERING FLIGHTFor standardization purposes, this discussion assumesa stationary hover in a no-wind condition. During hov-ering flight, a helicopter maintains a constant positionover a selected point, usually a few feet above theground. For a helicopter to hover, the lift and thrustproduced by the rotor system act straight up and mustequal the weight and drag, which act straight down.While hovering, you can change the amount of mainrotor thrust to maintain the desired hovering altitude.This is done by changing the angle of attack of the mainrotor blades and by varying power, as needed. In thiscase, thrust acts in the same vertical direction as lift.[Figure 3-1]

The weight that must be supported is the total weight of thehelicopter and its occupants. If the amount of thrust isgreater than the actual weight, the helicopter gains altitude;if thrust is less than weight, the helicopter loses altitude.

The drag of a hovering helicopter is mainly induced dragincurred while the blades are producing lift. There is,however, some profile drag on the blades as they rotatethrough the air. Throughout the rest of this discussion,the term “drag” includes both induced and profile drag.

An important consequence of producing thrust istorque. As stated before, for every action there is anequal and opposite reaction. Therefore, as the engineturns the main rotor system in a counterclockwisedirection, the helicopter fuselage turns clockwise. Theamount of torque is directly related to the amount ofengine power being used to turn the main rotor system.Remember, as power changes, torque changes.

To counteract this torque-induced turning tendency, anantitorque rotor or tail rotor is incorporated into mosthelicopter designs. You can vary the amount of thrustproduced by the tail rotor in relation to the amount oftorque produced by the engine. As the engine suppliesmore power, the tail rotor must produce more thrust.This is done through the use of antitorque pedals.

TRANSLATING TENDENCY OR DRIFTDuring hovering flight, a single main rotor helicopter tendsto drift in the same direction as antitorque rotor thrust. Thisdrifting tendency is called translating tendency. [Figure 3-2]

Thrust

Lift

Weight

Drag

Figure 3-1. To maintain a hover at a constant altitude, enoughlift and thrust must be generated to equal the weight of thehelicopter and the drag produced by the rotor blades.

Blade Rotation

Torque

TorqueDrift

Tail Rotor Thrust

Figure 3-2. A tail rotor is designed to produce thrust in adirection opposite torque. The thrust produced by the tailrotor is sufficient to move the helicopter laterally.

3-2

greater the centrifugal force. This force gives the rotorblades their rigidity and, in turn, the strength to supportthe weight of the helicopter. The centrifugal force gen-erated determines the maximum operating rotor r.p.m.due to structural limitations on the main rotor system.

As a vertical takeoff is made, two major forces are act-ing at the same time—centrifugal force acting outwardand perpendicular to the rotor mast, and lift actingupward and parallel to the mast. The result of these twoforces is that the blades assume a conical path insteadof remaining in the plane perpendicular to the mast.[Figure 3-4]

CORIOLIS EFFECT (LAW OF CONSERVATION OF ANGULAR MOMENTUM)Coriolis Effect, which is sometimes referred to as con-servation of angular momentum, might be compared tospinning skaters. When they extend their arms, theirrotation slows down because the center of mass movesfarther from the axis of rotation. When their arms areretracted, the rotation speeds up because the center ofmass moves closer to the axis of rotation.

When a rotor blade flaps upward, the center of mass ofthat blade moves closer to the axis of rotation and bladeacceleration takes place in order to conserve angularmomentum. Conversely, when that blade flaps down-ward, its center of mass moves further from the axis of

Before Takeoff

During Takeoff

Lift

Centrifugal Force

Resultant Blade Angle

Figure 3-4. Rotor blade coning occurs as the rotor bladesbegin to lift the weight of the helicopter. In a semirigid andrigid rotor system, coning results in blade bending. In anarticulated rotor system, the blades assume an upward anglethrough movement about the flapping hinges.

Centrifugal Force—The apparentforce that an object moving alonga circular path exerts on the bodyconstraining the obect and thatacts outwardy away from the cen-ter of rotation.

To counteract this drift, one or more of the followingfeatures may be used:

• The main transmission is mounted so that the rotormast is rigged for the tip-path plane to have a built-in tilt opposite tail thrust, thus producing a smallsideward thrust.

• Flight control rigging is designed so that the rotordisc is tilted slightly opposite tail rotor thrust whenthe cyclic is centered.

• The cyclic pitch control system is designed so thatthe rotor disc tilts slightly opposite tail rotor thrustwhen in a hover.

Counteracting translating tendency, in a helicopter with acounterclockwise main rotor system, causes the left skidto hang lower while hovering. The opposite is true forrotor systems turning clockwise when viewed from above.

PENDULAR ACTIONSince the fuselage of the helicopter, with a single mainrotor, is suspended from a single point and has consider-able mass, it is free to oscillate either longitudinally orlaterally in the same way as a pendulum. This pendularaction can be exaggerated by over controlling; therefore,control movements should be smooth and not exagger-ated. [Figure 3-3]

CONINGIn order for a helicopter to generate lift, the rotor bladesmust be turning. This creates a relative wind that isopposite the direction of rotor system rotation. The rotation of the rotor system creates centrifugal force(inertia), which tends to pull the blades straight outwardfrom the main rotor hub. The faster the rotation, the

Hover

Rearward Flight

Forward Flight

Figure 3-3. Because the helicopter’s body has mass and issuspended from a single point (the rotor mast head), it tendsto act much like a pendulum.

3-3

rotation and blade deceleration takes place. [Figure 3-5]Keep in mind that due to coning, a rotor blade will notflap below a plane passing through the rotor hub andperpendicular to the axis of rotation. The accelerationand deceleration actions of the rotor blades are absorbedby either dampers or the blade structure itself, depend-ing upon the design of the rotor system.

Two-bladed rotor systems are normally subject toCoriolis Effect to a much lesser degree than are articu-lated rotor systems since the blades are generally“underslung” with respect to the rotor hub, and thechange in the distance of the center of mass from theaxis of rotation is small. [Figure 3-6] The huntingaction is absorbed by the blades through bending. If atwo-bladed rotor system is not “underslung,” it will be

subject to Coriolis Effect comparable to that of a fullyarticulated system.

GROUND EFFECTWhen hovering near the ground, a phenomenon knownas ground effect takes place. [Figure 3-7] This effectusually occurs less than one rotor diameter above thesurface. As the induced airflow through the rotor disc isreduced by the surface friction, the lift vector increases.This allows a lower rotor blade angle for the sameamount of lift, which reduces induced drag. Groundeffect also restricts the generation of blade tip vorticesdue to the downward and outward airflow making alarger portion of the blade produce lift. When the heli-copter gains altitude vertically, with no forward air-speed, induced airflow is no longer restricted, and theblade tip vortices increase with the decrease in outwardairflow. As a result, drag increases which means a

Axis of Rotation

Blade Flapping

Center of Mass

Figure 3-5. The tendency of a rotor blade to increase ordecrease its velocity in its plane of rotation due to massmovement is known as Coriolis Effect, named for the mathe-matician who made studies of forces generated by radialmovements of mass on a rotating disc.

Large Blade Tip Vortex

No Wind HoverBlade Tip Vortex

OUT OF GROUND EFFECT (OGE) IN GROUND EFFECT (IGE)

Downwash Pattern Equidistant 360°

Figure 3-7. Air circulation patterns change when hovering out of ground effect (OGE) and when hovering in ground effect (IGE).

This elbow moves away from the mast as the rotor is tilted.

This elbow moves toward the mast as the rotor is tilted.

Mast Axis

CM CM

CM

CM

Figure 3-6. Because of the underslung rotor, the center ofmass remains approximately the same distance from themast after the rotor is tilted.

3-4

higher pitch angle, and more power is needed to movethe air down through the rotor.

Ground effect is at its maximum in a no-wind conditionover a firm, smooth surface. Tall grass, rough terrain,revetments, and water surfaces alter the airflow pattern,causing an increase in rotor tip vortices.

GYROSCOPIC PRECESSIONThe spinning main rotor of a helicopter acts like a gyro-scope. As such, it has the properties of gyroscopicaction, one of which is precession. Gyroscopic preces-sion is the resultant action or deflection of a spinningobject when a force is applied to this object. This actionoccurs approximately 90° in the direction of rotationfrom the point where the force is applied. [Figure 3-8]

Let us look at a two-bladed rotor system to see howgyroscopic precession affects the movement of the tip-path plane. Moving the cyclic pitch control increasesthe angle of attack of one rotor blade with the resultthat a greater lifting force is applied at that point in theplane of rotation. This same control movement simul-taneously decreases the angle of attack of the otherblade the same amount, thus decreasing the lifting forceapplied at that point in the plane of rotation. The bladewith the increased angle of attack tends to flap up; theblade with the decreased angle of attack tends to flapdown. Because the rotor disk acts like a gyro, theblades reach maximum deflection at a point approxi-mately 90° later in the plane of rotation. As shown infigure 3-9, the retreating blade angle of attack isincreased and the advancing blade angle of attack isdecreased resulting in a tipping forward of the tip-pathplane, since maximum deflection takes place 90° laterwhen the blades are at the rear and front, respectively.

In a rotor system using three or more blades, the move-ment of the cyclic pitch control changes the angle ofattack of each blade an appropriate amount so that theend result is the same.

VERTICAL FLIGHTHovering is actually an element of vertical flight.Increasing the angle of attack of the rotor blades (pitch)while their velocity remains constant generates addi-tional vertical lift and thrust and the helicopter ascends.Decreasing the pitch causes the helicopter to descend.In a no wind condition when lift and thrust are less thanweight and drag, the helicopter descends vertically. If

90°

Axis

Upward Force

Applied Here

Reaction Occurs Here

New Axis

Gyro Tips Down Here

Gyro Tips Up Here

Old Axis

Figure 3-8. Gyroscopic precession principle—when a force is applied to a spinning gyro, the maximum reaction occurs approx-imately 90° later in the direction of rotation.

Blade Rotation

Angle of Attack Decreased

Maximum Upward

Deflection

Maximum Downward Deflection Angle of Attack

Increased

Figure 3-9. With a counterclockwise main rotor blade rota-tion, as each blade passes the 90° position on the left, themaximum increase in angle of attack occurs. As each bladepasses the 90° position to the right, the maximum decreasein angle of attack occurs. Maximum deflection takes place90° later—maximum upward deflection at the rear and maxi-mum downward deflection at the front—and the tip-pathplane tips forward.

3-5

lift and thrust are greater than weight and drag, the hel-icopter ascends vertically. [Figure 3-10]

FORWARD FLIGHTIn or during forward flight, the tip-path plane is tilted for-ward, thus tilting the total lift-thrust force forward fromthe vertical. This resultant lift-thrust force can be resolvedinto two components—lift acting vertically upward andthrust acting horizontally in the direction of flight. Inaddition to lift and thrust, there is weight (the downwardacting force) and drag (the rearward acting or retardingforce of inertia and wind resistance). [Figure 3-11]

In straight-and-level, unaccelerated forward flight, liftequals weight and thrust equals drag (straight-and-levelflight is flight with a constant heading and at a constantaltitude). If lift exceeds weight, the helicopter climbs;if lift is less than weight, the helicopter descends. Ifthrust exceeds drag, the helicopter speeds up; if thrustis less than drag, it slows down.

As the helicopter moves forward, it begins to lose alti-tude because of the lift that is lost as thrust is divertedforward. However, as the helicopter begins to acceler-ate, the rotor system becomes more efficient due to theincreased airflow. The result is excess power over thatwhich is required to hover. Continued accelerationcauses an even larger increase in airflow through therotor disc and more excess power.

TRANSLATIONAL LIFTTranslational lift is present with any horizontal flow ofair across the rotor. This increased flow is most notice-able when the airspeed reaches approximately 16 to 24knots. As the helicopter accelerates through this speed,the rotor moves out of its vortices and is in relativelyundisturbed air. The airflow is also now more horizontal,which reduces induced flow and drag with a correspon-ding increase in angle of attack and lift. The additionallift available at this speed is referred to as “effectivetranslational lift” (ETL). [Figure 3-12]

When a single-rotor helicopter flies through translationallift, the air flowing through the main rotor and over thetail rotor becomes less turbulent and more aerodynami-cally efficient. As the tail rotor efficiency improves,more thrust is produced causing the aircraft to yaw leftin a counterclockwise rotor system. It will be necessaryto use right torque pedal to correct for this tendency ontakeoff. Also, if no corrections are made, the nose risesor pitches up, and rolls to the right. This is caused bycombined effects of dissymmetry of lift and transverseflow effect, and is corrected with cyclic control.

Resultant

Resultant

Lift

Thrust

Helicopter Movement

Weight

Drag

Figure 3-11. To transition into forward flight, some of the ver-tical thrust must be vectored horizontally. You initiate this byforward movement of the cyclic control.

No Recirculation of Air

More Horizontal Flow of Air

Reduced Induced Flow Increases Angle of Attack

Tail Rotor Operates in Relatively Clean Air

16 to 24 Knots

Figure 3-12. Effective translational lift is easily recognized inactual flight by a transient induced aerodynamic vibrationand increased performance of the helicopter.

Thrust

Lift

Weight

Drag

Vertical Ascent

Figure 3-10. To ascend vertically, more lift and thrust must be

generated to overcome the forces of weight and the drag.

3-6

Translational lift is also present in a stationary hover ifthe wind speed is approximately 16 to 24 knots. In nor-mal operations, always utilize the benefit of translationallift, especially if maximum performance is needed.

INDUCED FLOWAs the rotor blades rotate they generate what is calledrotational relative wind. This airflow is characterizedas flowing parallel and opposite the rotor’s plane ofrotation and striking perpendicular to the rotor blade’sleading edge. This rotational relative wind is used togenerate lift. As rotor blades produce lift, air is acceler-ated over the foil and projected downward. Anytime ahelicopter is producing lift, it moves large masses of airvertically and down through the rotor system. Thisdownwash or induced flow can significantly changethe efficiency of the rotor system. Rotational relativewind combines with induced flow to form the resultantrelative wind. As induced flow increases, resultant rel-ative wind becomes less horizontal. Since angle ofattack is determined by measuring the differencebetween the chord line and the resultant relative wind,as the resultant relative wind becomes less horizontal,angle of attack decreases. [Figure 3-13]

TRANSVERSE FLOW EFFECTAs the helicopter accelerates in forward flight, inducedflow drops to near zero at the forward disc area andincreases at the aft disc area. This increases the angleof attack at the front disc area causing the rotor blade toflap up, and reduces angle of attack at the aft disc areacausing the rotor blade to flap down. Because the rotoracts like a gyro, maximum displacement occurs 90° inthe direction of rotation. The result is a tendency forthe helicopter to roll slightly to the right as it acceler-

ates through approximately 20 knots or if the headwindis approximately 20 knots.

You can recognize transverse flow effect because ofincreased vibrations of the helicopter at airspeeds justbelow effective translational lift on takeoff and afterpassing through effective translational lift during land-ing. To counteract transverse flow effect, a cyclic inputneeds to be made.

DISSYMMETRY OF LIFTWhen the helicopter moves through the air, the relativeairflow through the main rotor disc is different on theadvancing side than on the retreating side. The relativewind encountered by the advancing blade is increasedby the forward speed of the helicopter, while the rela-tive wind speed acting on the retreating blade isreduced by the helicopter’s forward airspeed.Therefore, as a result of the relative wind speed, theadvancing blade side of the rotor disc produces morelift than the retreating blade side. This situation isdefined as dissymmetry of lift. [Figure 3-14]

If this condition was allowed to exist, a helicopter witha counterclockwise main rotor blade rotation would rollto the left because of the difference in lift. In reality, themain rotor blades flap and feather automatically toequalize lift across the rotor disc. Articulated rotor sys-tems, usually with three or more blades, incorporate ahorizontal hinge (flapping hinge) to allow the individ-ual rotor blades to move, or flap up and down as theyrotate. A semirigid rotor system (two blades) utilizes ateetering hinge, which allows the blades to flap as aunit. When one blade flaps up, the other flaps down.

Figure 3-13. A helicopter in forward flight, or hovering with a headwind or crosswind, has more molecules of air entering the aftportion of the rotor blade. Therefore, the angle of attack is less and the induced flow is greater at the rear of the rotor disc.

Resultant Relative Wind

Resultant Relative Wind

10 to 20 Knots

A

A

B

B

Induced Flow

Induced Flow

Angle of Attack Angle of

Attack

Rotational Relative Wind Rotational Relative Wind

3-7

As shown in figure 3-15, as the rotor blade reaches theadvancing side of the rotor disc (A), it reaches its max-imum upflap velocity. When the blade flaps upward,the angle between the chord line and the resultant rela-tive wind decreases. This decreases the angle of attack,

which reduces the amount of lift produced by the blade.At position (C) the rotor blade is now at its maximumdownflapping velocity. Due to downflapping, the anglebetween the chord line and the resultant relative windincreases. This increases the angle of attack and thusthe amount of lift produced by the blade.

The combination of blade flapping and slow relative windacting on the retreating blade normally limits the maxi-mum forward speed of a helicopter. At a high forwardspeed, the retreating blade stalls because of a high angle ofattack and slow relative wind speed. This situation iscalled retreating blade stall and is evidenced by a nosepitch up, vibration, and a rolling tendency—usually to theleft in helicopters with counterclockwise blade rotation.

You can avoid retreating blade stall by not exceedingthe never-exceed speed. This speed is designated VNEand is usually indicated on a placard and marked on theairspeed indicator by a red line.

During aerodynamic flapping of the rotor blades as theycompensate for dissymmetry of lift, the advancing blade

Rel

ativ

eW

ind

Rel

ativ

eW

ind

Direction of Flight

Advancing Side

Blade Tip Speed Plus Helicopter

Speed (400 KTS)

Blade Tip Speed Minus

Helicopter Speed

(200 KTS)

Retreating Side

Forward Flight 100 KTS

Blade Rotation

Figure 3-14. The blade tip speed of this helicopter is approxi-mately 300 knots. If the helicopter is moving forward at 100knots, the relative wind speed on the advancing side is 400knots. On the retreating side, it is only 200 knots. This differ-ence in speed causes a dissymmetry of lift.

Figure 3-15. The combined upward flapping (reduced lift) of the advancing blade and downward flapping (increased lift) of theretreating blade equalizes lift across the main rotor disc counteracting dissymmetry of lift.

Direction of Rotation

Chord Line

Resultant RW

Chord Line

Resultant RW

Chord Line

Downflap Velocity

Resultant RW

Chord Line

Resultant RW

Upflap Velocity

Angle of Attack at 9 O'Clock Position

Angle of Attack at 3 O'Clock Position

Angle of Attack over Tail

Angle of Attack over Nose

A

B

C

D

D

A

B

C

RW = Relative Wind = Angle of Attack

VNE —The speed beyond which an aircraft should never beoperated. VNE can change with altitude, density altitude, andweight.

3-8

ward. Drag now acts forward with the lift componentstraight up and weight straight down. [Figure 3-18]

TURNING FLIGHTIn forward flight, the rotor disc is tilted forward, whichalso tilts the total lift-thrust force of the rotor disc for-ward. When the helicopter is banked, the rotor disc istilted sideward resulting in lift being separated into twocomponents. Lift acting upward and opposing weight iscalled the vertical component of lift. Lift acting hori-zontally and opposing inertia (centrifugal force) is thehorizontal component of lift (centripetal force).[Figure 3-19]

As the angle of bank increases, the total lift force is tiltedmore toward the horizontal, thus causing the rate of turnto increase because more lift is acting horizontally. Sincethe resultant lifting force acts more horizontally, theeffect of lift acting vertically is deceased. To compen-sate for this decreased vertical lift, the angle of attack ofthe rotor blades must be increased in order to maintainaltitude. The steeper the angle of bank, the greater theangle of attack of the rotor blades required to maintainaltitude. Thus, with an increase in bank and a greaterangle of attack, the resultant lifting force increases andthe rate of turn is faster.

AUTOROTATIONAutorotation is the state of flight where the main rotorsystem is being turned by the action of relative wind

Centripetal Force—The forceopposite centrifugal force andattracts a body toward its axis ofrotation.

ResultantLift

Thrust

Drag

Resultant

Weight

Helicopter Movement

Figure 3-18. Forces acting on the helicopter during rearwardflight.

achieves maximum upflapping displacement over thenose and maximum downflapping displacement over thetail. This causes the tip-path plane to tilt to the rear and isreferred to as blowback. Figure 3-16 shows how the rotordisc was originally oriented with the front down follow-ing the initial cyclic input, but as airspeed is gained andflapping eliminates dissymmetry of lift, the front of thedisc comes up, and the back of the disc goes down. Thisreorientation of the rotor disc changes the direction inwhich total rotor thrust acts so that the helicopter’s for-ward speed slows, but can be corrected with cyclic input.

SIDEWARD FLIGHTIn sideward flight, the tip-path plane is tilted in the direc-tion that flight is desired. This tilts the total lift-thrustvector sideward. In this case, the vertical or lift compo-nent is still straight up and weight straight down, but thehorizontal or thrust component now acts sideward withdrag acting to the opposite side. [Figure 3-17]

REARWARD FLIGHTFor rearward flight, the tip-path plane is tilted rear-ward, which, in turn, tilts the lift-thrust vector rear-

Helicopter Movement

Weight

Drag

Resultant

Thrust

Lift

Figure 3-17. Forces acting on the helicopter during sidewardflight.

Figure 3-16. To compensate for blowback, you must movethe cyclic forward. Blowback is more pronounced with higherairspeeds.

3-9

rather than engine power. It is the means by which ahelicopter can be landed safely in the event of anengine failure. In this case, you are using altitude aspotential energy and converting it to kinetic energy dur-ing the descent and touchdown. All helicopters musthave this capability in order to be certified.Autorotation is permitted mechanically because of afreewheeling unit, which allows the main rotor to con-

tinue turning even if the engine is not running. In nor-mal powered flight, air is drawn into the main rotor sys-tem from above and exhausted downward. Duringautorotation, airflow enters the rotor disc from belowas the helicopter descends. [Figure 3-20]

AUTOROTATION (VERTICAL FLIGHT)Most autorotations are performed with forward speed.For simplicity, the following aerodynamic explanationis based on a vertical autorotative descent (no forwardspeed) in still air. Under these conditions, the forcesthat cause the blades to turn are similar for all bladesregardless of their position in the plane of rotation.Therefore, dissymmetry of lift resulting from helicop-ter airspeed is not a factor.

During vertical autorotation, the rotor disc is dividedinto three regions as illustrated in figure 3-21—the

Figure 3-20. During an autorotation, the upward flow of relative wind permits the main rotor blades to rotate at their normalspeed. In effect, the blades are “gliding” in their rotational plane.

Figure 3-21. Blade regions in vertical autorotation descent.

Figure 3-19. The horizontal component of lift accelerates thehelicopter toward the center of the turn.

Centripetal Force (Horizontal Component of Lift)

Vertical Component

of Lift

Bank Angle

Resultant Lift

Weight

Centrifugal Force (Inertia)

Normal Powered Flight Autorotation

Direction

of FlightDire

ctio

n

of Flight

Stall Region 25%

Driven Region 30% Driving

Region 45%

3-10

driven region, the driving region, and the stall region.Figure 3-22 shows four blade sections that illustrateforce vectors. Part A is the driven region, B and D arepoints of equilibrium, part C is the driving region, andpart E is the stall region. Force vectors are different ineach region because rotational relative wind is slowernear the blade root and increases continually towardthe blade tip. Also, blade twist gives a more positive

angle of attack in the driving region than in the drivenregion. The combination of the inflow up through therotor with rotational relative wind produces differentcombinations of aerodynamic force at every pointalong the blade.

The driven region, also called the propeller region, isnearest the blade tips. Normally, it consists of about 30

Figure 3-22. Force vectors in vertical autorotation descent.

B & D

Rotational Relative Wind

Lift

TAF

TAF

Total Aerodynamic Force Aft of Axis of Rotation

Total Aerodynamic Force Forward of Axis of Rotation

Angle of Attack 2° Drag

Chord Line

Inflow Up Through Rotor

Resultant Relative Wind

Equilibrium

Drag

Inflow TAF

Angle of Attack 6°

Drag Driving Region

Inflow

Axis of Rotation

Angle of Attack 24°

(Blade is Stalled)

TAFDrag

Stall Region

Inflow

Driven Range

A

B

C

D

E

Driven Region

Drag

Point of Equilibrium

Point of Equilibrium

Driving Region

Stall Region

Drag

Aut

orot

ativ

eF

orce

A

B & D

C

E

E

D

C

B

A

Lift

Lift

Lift

3-11

percent of the radius. In the driven region, part A of fig-ure 3-22, the total aerodynamic force acts behind theaxis of rotation, resulting in a overall drag force. Thedriven region produces some lift, but that lift is offsetby drag. The overall result is a deceleration in the rota-tion of the blade. The size of this region varies with theblade pitch, rate of descent, and rotor r.p.m. Whenchanging autorotative r.p.m., blade pitch, or rate ofdescent, the size of the driven region in relation to theother regions also changes.

There are two points of equilibrium on the blade—onebetween the driven region and the driving region, andone between the driving region and the stall region. Atpoints of equilibrium, total aerodynamic force isaligned with the axis of rotation. Lift and drag are pro-duced, but the total effect produces neither accelerationnor deceleration.

The driving region, or autorotative region, normallylies between 25 to 70 percent of the blade radius. PartC of figure 3-22 shows the driving region of the blade,which produces the forces needed to turn the bladesduring autorotation. Total aerodynamic force in thedriving region is inclined slightly forward of the axis ofrotation, producing a continual acceleration force. Thisinclination supplies thrust, which tends to acceleratethe rotation of the blade. Driving region size varieswith blade pitch setting, rate of descent, and rotor r.p.m.

By controlling the size of this region you can adjustautorotative r.p.m. For example, if the collective pitchis raised, the pitch angle increases in all regions. Thiscauses the point of equilibrium to move inboard alongthe blade’s span, thus increasing the size of the drivenregion. The stall region also becomes larger while thedriving region becomes smaller. Reducing the size ofthe driving region causes the acceleration force of thedriving region and r.p.m. to decrease.

The inner 25 percent of the rotor blade is referred to asthe stall region and operates above its maximum angleof attack (stall angle) causing drag which tends to slow

rotation of the blade. Part E of figure 3-22 depicts thestall region.

A constant rotor r.p.m. is achieved by adjusting the col-lective pitch so blade acceleration forces from the driv-ing region are balanced with the deceleration forcesfrom the driven and stall regions.

AUTOROTATION (FORWARD FLIGHT)Autorotative force in forward flight is produced inexactly the same manner as when the helicopter isdescending vertically in still air. However, because for-ward speed changes the inflow of air up through therotor disc, all three regions move outboard along theblade span on the retreating side of the disc where angleof attack is larger, as shown in figure 3-23. With lowerangles of attack on the advancing side blade, more ofthat blade falls in the driven region. On the retreatingside, more of the blade is in the stall region. A smallsection near the root experiences a reversed flow, there-fore the size of the driven region on the retreating sideis reduced.

Figure 3-23. Blade regions in forward autorotation descent.

Forward

Driven Region

Driving Region

Retreating Side

Stall Region

Advancing Side

3-12

4-1

Note: In this chapter, it is assumed that the helicopter hasa counterclockwise main rotor blade rotation as viewedfrom above. If flying a helicopter with a clockwise rota-tion, you will need to reverse left and right references,particularly in the areas of rotor blade pitch change, anti-torque pedal movement, and tail rotor thrust.

There are four basic controls used during flight. Theyare the collective pitch control, the throttle, the cyclicpitch control, and the antitorque pedals.

COLLECTIVE PITCH CONTROLThe collective pitch control, located on the left side ofthe pilot’s seat, changes the pitch angle of all main rotorblades simultaneously, or collectively, as the nameimplies. As the collective pitch control is raised, thereis a simultaneous and equal increase in pitch angle ofall main rotor blades; as it is lowered, there is a simul-taneous and equal decrease in pitch angle. This is donethrough a series of mechanical linkages and the amountof movement in the collective lever determines theamount of blade pitch change. [Figure 4-1] An

adjustable friction control helps prevent inadvertentcollective pitch movement.

Changing the pitch angle on the blades changes theangle of attack on each blade. With a change in angleof attack comes a change in drag, which affects thespeed or r.p.m. of the main rotor. As the pitch angleincreases, angle of attack increases, drag increases,and rotor r.p.m. decreases. Decreasing pitch angledecreases both angle of attack and drag, while rotorr.p.m. increases. In order to maintain a constant rotorr.p.m., which is essential in helicopter operations, aproportionate change in power is required to com-pensate for the change in drag. This is accomplishedwith the throttle control or a correlator and/or gover-nor, which automatically adjusts engine power.

THROTTLE CONTROLThe function of the throttle is to regulate engine r.p.m.If the correlator or governor system does not maintainthe desired r.p.m. when the collective is raised or low-ered, or if those systems are not installed, the throttle

Figure 4-1. Raising the collective pitch control increases the pitch angle the same amount on all blades.

4-2

has to be moved manually with the twist grip in orderto maintain r.p.m. Twisting the throttle outboardincreases r.p.m.; twisting it inboard decreases r.p.m.[Figure 4-2]

COLLECTIVE PITCH / THROTTLECOORDINATIONWhen the collective pitch is raised, the load on theengine is increased in order to maintain desired r.p.m.The load is measured by a manifold pressure gaugein piston helicopters or by a torque gauge in turbinehelicopters.

In piston helicopters, the collective pitch is the primarycontrol for manifold pressure, and the throttle is the pri-mary control for r.p.m. However, the collective pitchcontrol also influences r.p.m., and the throttle alsoinfluences manifold pressure; therefore, each is consid-ered to be a secondary control of the other’s function.Both the tachometer (r.p.m. indicator) and the manifoldpressure gauge must be analyzed to determine whichcontrol to use. Figure 4-3 illustrates this relationship.

CORRELATOR / GOVERNORA correlator is a mechanical connection between thecollective lever and the engine throttle. When the col-lective lever is raised, power is automatically increasedand when lowered, power is decreased. This systemmaintains r.p.m. close to the desired value, but stillrequires adjustment of the throttle for fine tuning.

A governor is a sensing device that senses rotor andengine r.p.m. and makes the necessary adjustments inorder to keep rotor r.p.m. constant. In normal operations,once the rotor r.p.m. is set, the governor keeps the r.p.m.constant, and there is no need to make any throttle adjust-ments. Governors are common on all turbine helicoptersand used on some piston powered helicopters.

Some helicopters do not have correlators or governorsand require coordination of all collective and throttlemovements. When the collective is raised, the throttlemust be increased; when the collective is lowered, thethrottle must be decreased. As with any aircraft control,large adjustments of either collective pitch or throttleshould be avoided. All corrections should be madethrough the use of smooth pressure.

CYCLIC PITCH CONTROLThe cyclic pitch control tilts the main rotor disc bychanging the pitch angle of the rotor blades in theircycle of rotation. When the main rotor disc is tilted, thehorizontal component of lift moves the helicopter inthe direction of tilt. [Figure 4-4]

Figure 4-2. A twist grip throttle is usually mounted on the endof the collective lever. Some turbine helicopters have thethrottles mounted on the overhead panel or on the floor inthe cockpit.

If Manifold Pressure

is

and R.P.M.

is

Solution

Low

Low

Low

LowHigh

High

High

High

Increasing the throttle increases manifold pressure and r.p.m.

Lowering the collective pitch decreases manifold pressure and increases r.p.m.

Raising the collective pitch increases manifold pressure and decreases r.p.m.

Reducing the throttle decreases manifold pressure and r.p.m.

Figure 4-3. Relationship between manifold pressure, r.p.m.,collective, and throttle.

Figure 4-4. The cyclic pitch control may be mounted verti-cally between the pilot’s knees or on a teetering bar from asingle cyclic located in the center of the helicopter. The cycliccan pivot in all directions.

4-3

The rotor disc tilts in the direction that pressure is appliedto the cyclic pitch control. If the cyclic is moved forward,the rotor disc tilts forward; if the cyclic is moved aft, thedisc tilts aft, and so on. Because the rotor disc acts like agyro, the mechanical linkages for the cyclic control rodsare rigged in such a way that they decrease the pitch angleof the rotor blade approximately 90° before it reaches thedirection of cyclic displacement, and increase the pitchangle of the rotor blade approximately 90° after it passesthe direction of displacement. An increase in pitch angleincreases angle of attack; a decrease in pitch angledecreases angle of attack. For example, if the cyclic ismoved forward, the angle of attack decreases as the rotorblade passes the right side of the helicopter and increaseson the left side. This results in maximum downwarddeflection of the rotor blade in front of the helicopter andmaximum upward deflection behind it, causing the rotordisc to tilt forward.

ANTITORQUE PEDALSThe antitorque pedals, located on the cabin floor by thepilot’s feet, control the pitch, and therefore the thrust,of the tail rotor blades. [Figure 4-5] . The main purposeof the tail rotor is to counteract the torque effect of themain rotor. Since torque varies with changes in power,the tail rotor thrust must also be varied. The pedals areconnected to the pitch change mechanism on the tailrotor gearbox and allow the pitch angle on the tail rotorblades to be increased or decreased.

HEADING CONTROLBesides counteracting torque of the main rotor, the tailrotor is also used to control the heading of the helicopterwhile hovering or when making hovering turns. Hoveringturns are commonly referred to as “pedal turns.”

In forward flight, the antitorque pedals are not used tocontrol the heading of the helicopter, except during por-tions of crosswind takeoffs and approaches. Instead theyare used to compensate for torque to put the helicopter inlongitudinal trim so that coordinated flight can be main-tained. The cyclic control is used to change heading bymaking a turn to the desired direction.

The thrust of the tail rotor depends on the pitch angle ofthe tail rotor blades. This pitch angle can be positive, neg-ative, or zero. A positive pitch angle tends to move the tailto the right. A negative pitch angle moves the tail to theleft, while no thrust is produced with a zero pitch angle.

With the right pedal moved forward of the neutral posi-tion, the tail rotor either has a negative pitch angle or asmall positive pitch angle. The farther it is forward, thelarger the negative pitch angle. The nearer it is to neu-tral, the more positive the pitch angle, and somewherein between, it has a zero pitch angle. As the left pedal ismoved forward of the neutral position, the positive pitchangle of the tail rotor increases until it becomes maxi-mum with full forward displacement of the left pedal.

If the tail rotor has a negative pitch angle, tail rotorthrust is working in the same direction as the torque ofthe main rotor. With a small positive pitch angle, thetail rotor does not produce sufficient thrust to overcomethe torque effect of the main rotor during cruise flight.Therefore, if the right pedal is displaced forward ofneutral during cruising flight, the tail rotor thrust doesnot overcome the torque effect, and the nose yaws tothe right. [Figure 4-6]

With the antitorque pedals in the neutral position, the tailrotor has a medium positive pitch angle. In medium pos-itive pitch, the tail rotor thrust approximately equals thetorque of the main rotor during cruise flight, so the heli-copter maintains a constant heading in level flight.

Figure 4-5. Antitorque pedals compensate for changes intorque and control heading in a hover.

Tail MovesTail MovesNegative or Low

Positive PitchMedium

Positive PitchHigh Positive

Pitch

Figure 4-6. Tail rotor pitch angle and thrust in relation to pedal positions during cruising flight.

4-4

If the left pedal is in a forward position, the tail rotorhas a high positive pitch position. In this position, tailrotor thrust exceeds the thrust needed to overcometorque effect during cruising flight so the helicopteryaws to the left.

The above explanation is based on cruise power and air-speed. Since the amount of torque is dependent on theamount of engine power being supplied to the main rotor,the relative positions of the pedals required to counteracttorque depend upon the amount of power being used atany time. In general, the less power being used, thegreater the requirement for forward displacement of the

right pedal; the greater the power, the greater the forwarddisplacement of the left pedal.

The maximum positive pitch angle of the tail rotor isgenerally somewhat greater than the maximum nega-tive pitch angle available. This is because the primarypurpose of the tail rotor is to counteract the torque ofthe main rotor. The capability for tail rotors to producethrust to the left (negative pitch angle) is necessary,because during autorotation the drag of the transmis-sion tends to yaw the nose to the left, or in the samedirection the main rotor is turning.

5-1

By knowing the various systems on a helicopter, youwill be able to more easily recognize potential problems,and if a problem arises, you will have a better under-standing of what to do to correct the situation.

ENGINESThe two most common types of engines used in heli-copters are the reciprocating engine and the turbineengine. Reciprocating engines, also called pistonengines, are generally used in smaller helicopters. Mosttraining helicopters use reciprocating engines becausethey are relatively simple and inexpensive to operate.Turbine engines are more powerful and are used in awide variety of helicopters. They produce a tremen-dous amount of power for their size but are generallymore expensive to operate.

RECIPROCATING ENGINEThe reciprocating engine consists of a series of pistonsconnected to a rotating crankshaft. As the pistons moveup and down, the crankshaft rotates. The reciprocatingengine gets its name from the back-and-forth movementof its internal parts. The four-stroke engine is the mostcommon type, and refers to the four different cycles theengine undergoes to produce power. [Figure 5-1]

When the piston moves away from the cylinder head onthe intake stroke, the intake valve opens and a mixtureof fuel and air is drawn into the combustion chamber.As the cylinder moves back towards the cylinder head,the intake valve closes, and the fuel/air mixture is com-pressed. When compression is nearly complete, thespark plugs fire and the compressed mixture is ignitedto begin the power stroke. The rapidly expanding gasesfrom the controlled burning of the fuel/air mixturedrive the piston away from the cylinder head, thus pro-viding power to rotate the crankshaft. The piston thenmoves back toward the cylinder head on the exhauststroke where the burned gasses are expelled throughthe opened exhaust valve.

Even when the engine is operated at a fairly low speed,the four-stroke cycle takes place several hundred timeseach minute. In a four-cylinder engine, each cylinderoperates on a different stroke. Continuous rotation of acrankshaft is maintained by the precise timing of thepower strokes in each cylinder.

TURBINE ENGINEThe gas turbine engine mounted on most helicopters ismade up of a compressor, combustion chamber, turbine,and gearbox assembly. The compressor compresses theair, which is then fed into the combustion chamberwhere atomized fuel is injected into it. The fuel/airmixture is ignited and allowed to expand. This com-bustion gas is then forced through a series of turbinewheels causing them to turn. These turbine wheelsprovide power to both the engine compressor and themain rotor system through an output shaft. The

Figure 5-1. The arrows in this illustration indicate the direc-tion of motion of the crankshaft and piston during the four-stroke cycle.

Intake Compression

Power Exhaust

Intake Valve

Exhaust Valve

Spark Plug

Piston

Connecting Rod

Crankshaft

1 2

3 4

5-2

combustion gas is finally expelled through an exhaustoutlet. [Figure 5-2]

COMPRESSORThe compressor may consist of an axial compressor, acentrifugal compressor, or both. An axial compressorconsists of two main elements, the rotor and the stator.The rotor consists of a number of blades fixed on arotating spindle and resembles a fan. As the rotorturns, air is drawn rearwards. Stator vanes are arrangedin fixed rows between the rotor blades and act as adiffuser at each stage to decrease air velocity andincrease air pressure. There may be a number of rowsof rotor blades and stator vanes. Each row constitutesa pressure stage, and the number of stages depends onthe amount of air and pressure rise required for theparticular engine.

A centrifugal compressor consists of an impeller, dif-fuser, and a manifold. The impeller, which is a forgeddisc with integral blades, rotates at a high speed todraw air in and expel it at an accelerated rate. The airthen passes through the diffuser which slows the airdown. When the velocity of the air is slowed, staticpressure increases, resulting in compressed, high-pres-sure air. The high pressure air then passes through thecompressor manifold where it is distributed to thecombustion chamber.

COMBUSTION CHAMBERUnlike a piston engine, the combustion in a turbineengine is continuous. An igniter plug serves only toignite the fuel/air mixture when starting the engine.Once the fuel/air mixture is ignited, it will continue toburn as long as the fuel/air mixture continues to bepresent. If there is an interruption of fuel, air, or both,combustion ceases. This is known as a “flame-out,” andthe engine has to be restarted or re-lit. Some helicoptersare equipped with auto-relight, which automaticallyactivates the igniters to start combustion if the engineflames out.

TURBINEThe turbine section consists of a series of turbinewheels that are used to drive the compressor sectionand the rotor system. The first stage, which is usuallyreferred to as the gas producer or N1 may consist ofone or more turbine wheels. This stage drives thecomponents necessary to complete the turbine cyclemaking the engine self-sustaining. Common compo-nents driven by the N1 stage are the compressor, oilpump, and fuel pump. The second stage, which mayalso consist of one or more wheels, is dedicated todriving the main rotor system and accessories fromthe engine gearbox. This is referred to as the powerturbine (N2 or Nr).

Compressor Discharge Air Tube

Exhaust Air Outlet

Igniter Plug

Fuel Nozzle

Air

Inlet

Output Shaft

Gear

Compressor Rotor Turbine to Compressor CouplingCombustion

Liner

N2

N1

Inlet Air Compressor Discharge Air Combustion Gasses Exhaust Gasses

Compression Section Gearbox Section Turbine Section Combustion Section

StatorRotor

Figure 5-2. Many helicopters use a turboshaft engine to drive the main transmission and rotor systems. The main differencebetween a turboshaft and a turbojet engine is that most of the energy produced by the expanding gases is used to drive a tur-bine rather than producing thrust through the expulsion of exhaust gases.

5-3

If the first and second stage turbines are mechanically cou-pled to each other, the system is said to be a direct-driveengine or fixed turbine. These engines share a commonshaft, which means the first and second stage turbines, andthus the compressor and output shaft, are connected.

On most turbine assemblies used in helicopters, thefirst stage and second stage turbines are not mechani-cally connected to each other. Rather, they are mountedon independent shafts and can turn freely with respect toeach other. This is referred to as a “free turbine.” Whenthe engine is running, the combustion gases passthrough the first stage turbine to drive the compressorrotor, and then past the independent second stage tur-bine, which turns the gearbox to drive the output shaft.

TRANSMISSION SYSTEMThe transmission system transfers power from theengine to the main rotor, tail rotor, and other acces-sories. The main components of the transmission sys-tem are the main rotor transmission, tail rotor drivesystem, clutch, and freewheeling unit. Helicopter trans-missions are normally lubricated and cooled with theirown oil supply. A sight gauge is provided to check theoil level. Some transmissions have chip detectorslocated in the sump. These detectors are wired to warn-ing lights located on the pilot’s instrument panel thatilluminate in the event of an internal problem.

MAIN ROTOR TRANSMISSIONThe primary purpose of the main rotor transmissionis to reduce engine output r.p.m. to optimum rotorr.p.m. This reduction is different for the various heli-copters, but as an example, suppose the engine r.p.m. ofa specific helicopter is 2,700. To achieve a rotor speed of450 r.p.m. would require a 6 to 1 reduction. A 9 to 1reduction would mean the rotor would turn at300 r.p.m.

Most helicopters use a dual-needle tachometer to showboth engine and rotor r.p.m. or a percentage of engineand rotor r.p.m. The rotor r.p.m. needle normally isused only during clutch engagement to monitor rotoracceleration, and in autorotation to maintain r.p.m.within prescribed limits. [Figure 5-3]

Chip Detector—A chip detector isa warning device that alerts you toany abnormal wear in a transmis-sion or engine. It consists of amagnetic plug located within thetransmission. The magnet attractsany ferrous metal particles thathave come loose from the bearingsor other transmission parts. Mostchip detectors send a signal tolights located on the instrumentpanel that illuminate when ferrousmetal particles are picked up.

In helicopters with horizontally mounted engines,another purpose of the main rotor transmission is tochange the axis of rotation from the horizontal axis ofthe engine to the vertical axis of the rotor shaft.

TAIL ROTOR DRIVE SYSTEMThe tail rotor drive system consists of a tail rotor driveshaft powered from the main transmission and a tailrotor transmission mounted at the end of the tail boom.The drive shaft may consist of one long shaft or a seriesof shorter shafts connected at both ends with flexiblecouplings. This allows the drive shaft to flex with thetail boom. The tail rotor transmission provides a rightangle drive for the tail rotor and may also include gear-ing to adjust the output to optimum tail rotor r.p.m.[Figure 5-4]

Figure 5-3. There are various types of dual-needle tachome-ters, however, when the needles are superimposed or married,the ratio of the engine r.p.m. is the same as the gear reductionratio.

Figure 5-4. The typical components of a tail rotor drive sys-tem are shown here.

Tail Rotor Transmission

Tail Rotor

Drive Shaft

Main Transmission

5-4

CLUTCHIn a conventional airplane, the engine and propeller arepermanently connected. However, in a helicopter thereis a different relationship between the engine and therotor. Because of the greater weight of a rotor in rela-tion to the power of the engine, as compared to theweight of a propeller and the power in an airplane, therotor must be disconnected from the engine when youengage the starter. A clutch allows the engine to bestarted and then gradually pick up the load of the rotor.

On free turbine engines, no clutch is required, as thegas producer turbine is essentially disconnected fromthe power turbine. When the engine is started, there islittle resistance from the power turbine. This enablesthe gas producer turbine to accelerate to normal idlespeed without the load of the transmission and rotorsystem dragging it down. As the gas pressure increasesthrough the power turbine, the rotor blades begin toturn, slowly at first and then gradually accelerate tonormal operating r.p.m.

On reciprocating helicopters, the two main types ofclutches are the centrifugal clutch and the belt drive clutch.

CENTRIFUGAL CLUTCHThe centrifugal clutch is made up of an inner assemblyand a outer drum. The inner assembly, which is con-nected to the engine driveshaft, consists of shoes linedwith material similar to automotive brake linings. Atlow engine speeds, springs hold the shoes in, so there isno contact with the outer drum, which is attached to thetransmission input shaft. As engine speed increases,centrifugal force causes the clutch shoes to move out-ward and begin sliding against the outer drum. Thetransmission input shaft begins to rotate, causing therotor to turn, slowly at first, but increasing as the frictionincreases between the clutch shoes and transmissiondrum. As rotor speed increases, the rotor tachometerneedle shows an increase by moving toward the enginetachometer needle. When the two needles are superim-posed, the engine and the rotor are synchronized,indicating the clutch is fully engaged and there is nofurther slippage of the clutch shoes.

BELT DRIVE CLUTCHSome helicopters utilize a belt drive to transmit powerfrom the engine to the transmission. A belt drive con-sists of a lower pulley attached to the engine, an upperpulley attached to the transmission input shaft, a beltor a series of V-belts, and some means of applyingtension to the belts. The belts fit loosely over theupper and lower pulley when there is no tension onthe belts. This allows the engine to be started withoutany load from the transmission. Once the engine isrunning, tension on the belts is gradually increased.When the rotor and engine tachometer needles aresuperimposed, the rotor and the engine are synchro-nized, and the clutch is then fully engaged.

Advantages of this system include vibration isolation,simple maintenance, and the ability to start and warmup the engine without engaging the rotor.

FREEWHEELING UNITSince lift in a helicopter is provided by rotating airfoils,these airfoils must be free to rotate if the engine fails. Thefreewheeling unit automatically disengages the enginefrom the main rotor when engine r.p.m. is less than mainrotor r.p.m. This allows the main rotor to continue turningat normal in-flight speeds. The most common freewheel-ing unit assembly consists of a one-way sprag clutchlocated between the engine and main rotor transmission.This is usually in the upper pulley in a piston helicopteror mounted on the engine gearbox in a turbine helicopter.When the engine is driving the rotor, inclined surfaces inthe spray clutch force rollers against an outer drum. Thisprevents the engine from exceeding transmission r.p.m. Ifthe engine fails, the rollers move inward, allowing theouter drum to exceed the speed of the inner portion. Thetransmission can then exceed the speed of the engine. Inthis condition, engine speed is less than that of the drivesystem, and the helicopter is in an autorotative state.

MAIN ROTOR SYSTEMMain rotor systems are classified according to how themain rotor blades move relative to the main rotor hub.As was described in Chapter 1—Introduction to theHelicopter, there are three basic classifications: fullyarticulated, semirigid, or rigid. Some modern rotor sys-tems use a combination of these types.

FULLY ARTICULATED ROTOR SYSTEMIn a fully articulated rotor system, each rotor blade isattached to the rotor hub through a series of hinges,which allow the blade to move independently of theothers. These rotor systems usually have three or moreblades. [Figure 5-5]

Pitch Change Axis

(Feathering)

Flapping Hinge

Damper

Drag Hinge

Pitch Horn

Figure 5-5. Each blade of a fully articulated rotor system canflap, drag, and feather independently of the other blades.

5-5

The horizontal hinge, called the flapping hinge, allowsthe blade to move up and down. This movement iscalled flapping and is designed to compensate for dis-symetry of lift. The flapping hinge may be located atvarying distances from the rotor hub, and there may bemore than one hinge.

The vertical hinge, called the lead-lag or drag hinge,allows the blade to move back and forth. This move-ment is called lead-lag, dragging, or hunting.Dampers are usually used to prevent excess backand forth movement around the drag hinge. The pur-pose of the drag hinge and dampers is to compensatefor the acceleration and deceleration caused byCoriolis Effect.

Each blade can also be feathered, that is, rotated aroundits spanwise axis. Feathering the blade means changingthe pitch angle of the blade. By changing the pitchangle of the blades you can control the thrust and direc-tion of the main rotor disc.

SEMIRIGID ROTOR SYSTEMA semirigid rotor system is usually composed of twoblades which are rigidly mounted to the main rotor hub.The main rotor hub is free to tilt with respect to themain rotor shaft on what is known as a teeteringhinge. This allows the blades to flap together as aunit. As one blade flaps up, the other flaps down.Since there is no vertical drag hinge, lead-lag forcesare absorbed through blade bending. [Figure 5-6]

RIGID ROTOR SYSTEMIn a rigid rotor system, the blades, hub, and mast arerigid with respect to each other. There are no vertical orhorizontal hinges so the blades cannot flap or drag, but

they can be feathered. Flapping and lead/lag forces areabsorbed by blade bending.

COMBINATION ROTOR SYSTEMSModern rotor systems may use the combined princi-ples of the rotor systems mentioned above. Somerotor hubs incorporate a flexible hub, which allowsfor blade bending (flexing) without the need for bear-ings or hinges. These systems, called flextures, areusually constructed from composite material.Elastomeric bearings may also be used in place ofconventional roller bearings. Elastomeric bearings arebearings constructed from a rubber type material andhave limited movement that is perfectly suited for hel-icopter applications. Flextures and elastomeric bear-ings require no lubrication and, therefore, require lessmaintenance. They also absorb vibration, whichmeans less fatigue and longer service life for the heli-copter components. [Figure 5-7]

SWASH PLATE ASSEMBLYThe purpose of the swash plate is to transmit controlinputs from the collective and cyclic controls to the mainrotor blades. It consists of two main parts: the stationary

Teetering Hinge

Feathering Hinge

Static Stops

Pitch Horn

Figure 5-6. On a semirigid rotor system, a teetering hingeallows the rotor hub and blades to flap as a unit. A static flap-ping stop located above the hub prevents excess rockingwhen the blades are stopped. As the blades begin to turn,centrifugal force pulls the static stops out of the way.

Figure 5-7. Rotor systems, such as Eurocopter’s Starflex orBell’s soft-in-plane, use composite material and elastomericbearings to reduce complexity and maintenance and,thereby, increase reliability.

5-6

swash plate and the rotating swash plate. [Figure 5-8]The stationary swash plate is mounted around the mainrotor mast and connected to the cyclic and collectivecontrols by a series of pushrods. It is restrained fromrotating but is able to tilt in all directions and move verti-cally. The rotating swash plate is mounted to the sta-tionary swash plate by means of a bearing and isallowed to rotate with the main rotor mast. Both swashplates tilt and slide up and down as one unit. The rotat-ing swash plate is connected to the pitch horns by thepitch links.

FUEL SYSTEMSThe fuel system in a helicopter is made up of twogroups of components: the fuel supply system and theengine fuel control system.

FUEL SUPPLY SYSTEMThe supply system consists of a fuel tank or tanks, fuelquantity gauges, a shut-off valve, fuel filter, a fuel lineto the engine, and possibly a primer and fuel pumps.[Figure 5-9]

The fuel tanks are usually mounted to the airframe asclose as possible to the center of gravity. This way, asfuel is burned off, there is a negligible effect on the cen-ter of gravity. A drain valve located on the bottom ofthe fuel tank allows the pilot to drain water and sedi-ment that may have collected in the tank. A fuel ventprevents the formation of a vacuum in the tank, and anoverflow drain allows for fuel to expand without rup-turing the tank. A fuel quantity gauge located on thepilot’s instrument panel shows the amount of fuelmeasured by a sensing unit inside the tank. Somegauges show tank capacity in both gallons and pounds.

The fuel travels from the fuel tank through a shut-offvalve, which provides a means to completely stop fuel

flow to the engine in the event of an emergency or fire.The shut-off valve remains in the open position for allnormal operations.

Most non-gravity feed fuel systems contain both anelectric pump and a mechanical engine driven pump.The electrical pump is used to maintain positive fuelpressure to the engine pump and also serves as abackup in the event of mechanical pump failure. Theelectrical pump is controlled by a switch in the cockpit.The engine driven pump is the primary pump that sup-plies fuel to the engine and operates any time theengine is running.

A fuel filter removes moisture and other sediment fromthe fuel before it reaches the engine. These contami-nants are usually heavier than fuel and settle to the bot-tom of the fuel filter sump where they can be drainedout by the pilot.

Some fuel systems contain a small hand-operated pumpcalled a primer. A primer allows fuel to be pumpeddirectly into the intake port of the cylinders prior toengine start. The primer is useful in cold weather whenfuel in the carburetor is difficult to vaporize.

ENGINE FUEL CONTROL SYSTEMThe purpose of the fuel control system is to bring out-side air into the engine, mix it with fuel in the properproportion, and deliver it to the combustion chamber.

Throttle

Low Level Warning Light

Vent

Fuel Quantity Gauge

Mixture Control

Fuel Shutoff

Primer

Tank

Shut-off Valve

Carburetor

Fuel Strainer

Primer Nozzle at Cylinder

Figure 5-9. A typical gravity feed fuel system, in a helicopterwith a reciprocating engine, contains the componentsshown here.

Stationary Swash Plate

Pitch Link

Rotating Swash

Plate

Control Rod

Figure 5-8. Collective and cyclic control inputs are transmit-ted to the stationary swash plate by control rods causing it totilt or to slide vertically. The pitch links attached from therotating swash plate to the pitch horns on the rotor hubtransmit these movements to the blades.

5-7

RECIPROCATING ENGINESFuel is delivered to the cylinders by either a carburetoror fuel injection system.

CARBURETORIn a carburetor system, air is mixed with vaporized fuel asit passes through a venturi in the carburetor. The meteredfuel/air mixture is then delivered to the cylinder intake.

Carburetors are calibrated at sea level, and the correctfuel-to-air mixture ratio is established at that altitudewith the mixture control set in the FULL RICH posi-tion. However, as altitude increases, the density of airentering the carburetor decreases while the density ofthe fuel remains the same. This means that at higheraltitudes, the mixture becomes progressively richer. Tomaintain the correct fuel/air mixture, you must be ableto adjust the amount of fuel that is mixed with theincoming air. This is the function of the mixture con-trol. This adjustment, often referred to as “leaning themixture,” varies from one aircraft to another. Refer tothe FAA-Approved Rotocraft Flight Manual (RFM) todetermine specific procedures for your helicopter. Notethat most manufacturers do not recommend leaning hel-icopters in-flight.

Most mixture adjustments are required during changes ofaltitude or during operations at airports with field eleva-tions well above sea level. A mixture that is too rich canresult in engine roughness and reduced power. The rough-ness normally is due to spark plug fouling from exces-sive carbon buildup on the plugs. This occurs becausethe excessively rich mixture lowers the temperature insidethe cylinder, inhibiting complete combustion of the fuel.This condition may occur during the pretakeoff runup athigh elevation airports and during climbs or cruise flightat high altitudes. Usually, you can correct the problem byleaning the mixture according to RFM instructions.

If you fail to enrich the mixture during a descent fromhigh altitude, it normally becomes too lean. Highengine temperatures can cause excessive engine wearor even failure. The best way to avoid this type of situ-ation is to monitor the engine temperature gauges regu-larly and follow the manufacturer’s guidelines formaintaining the proper mixture.

CARBURETOR ICEThe effect of fuel vaporization and decreasing air pres-sure in the venturi causes a sharp drop in temperaturein the carburetor. If the air is moist, the water vapor inthe air may condense. When the temperature in the car-buretor is at or below freezing, carburetor ice may formon internal surfaces, including the throttle valve.[Figure 5-10] Because of the sudden cooling that takesplace in the carburetor, icing can occur even on warm

days with temperatures as high as 38°C (100°F) andthe humidity as low as 50 percent. However, it is morelikely to occur when temperatures are below 21°C(70°F) and the relative humidity is above 80 percent.The likelihood of icing increases as temperaturedecreases down to 0°C (32°F), and as relative humidityincreases. Below freezing, the possibility of carburetoricing decreases with decreasing temperatures.

Although carburetor ice can occur during any phase offlight, it is particularly dangerous when you are usingreduced power, such as during a descent. You may notnotice it during the descent until you try to add power.

Indications of carburetor icing are a decrease in enginer.p.m. or manifold pressure, the carburetor air tempera-ture gauge indicating a temperature outside the safeoperating range, and engine roughness. Since changesin r.p.m. or manifold pressure can occur for a numberof reasons, it is best to closely check the carburetor airtemperature gauge when in possible carburetor icingconditions. Carburetor air temperature gauges aremarked with a yellow caution arc or green operatingarcs. You should refer to the FAA-Approved RotorcraftFlight Manual for the specific procedure as to whenand how to apply carburetor heat. However, in mostcases, you should keep the needle out of the yellow arcor in the green arc. This is accomplished by using a car-buretor heat system, which eliminates the ice by

To Engine

Incoming Air

Ice

Ice

Venturi

Fuel/Air Mixture

Ice

Figure 5-10. Carburetor ice reduces the size of the air pas-sage to the engine. This restricts the flow of the fuel/airmixture, and reduces power.

5-8

routing air across a heat source, such as an exhaustmanifold, before it enters the carburetor. [Figure 5-11].

FUEL INJECTIONIn a fuel injection system, fuel and air are metered atthe fuel control unit but are not mixed. The fuel isinjected directly into the intake port of the cylinderwhere it is mixed with the air just before entering thecylinder. This system ensures a more even fuel distri-bution in the cylinders and better vaporization, whichin turn, promotes more efficient use of fuel. Also, thefuel injection system eliminates the problem of carbu-retor icing and the need for a carburetor heat system.

TURBINE ENGINESThe fuel control system on the turbine engine is fairlycomplex, as it monitors and adjusts many differentparameters on the engine. These adjustments are doneautomatically and no action is required of the pilotother than starting and shutting down. No mixtureadjustment is necessary, and operation is fairly simpleas far as the pilot is concerned. New generation fuelcontrols incorporate the use of a full authority digitalengine control (FADEC) computer to control theengine’s fuel requirements. The FADEC systemsincrease efficiency, reduce engine wear, and alsoreduce pilot workload. The FADEC usually incorpo-rates back-up systems in the event of computer failure.

ELECTRICAL SYSTEMSThe electrical systems, in most helicopters, reflect theincreased use of sophisticated avionics and other elec-trical accessories. More and more operations in today’sflight environment are dependent on the aircraft’s elec-trical system; however, all helicopters can be safelyflown without any electrical power in the event of anelectrical malfunction or emergency.

Helicopters have either a 14- or 28-volt, direct-cur-rent electrical system. On small, piston powered helicopters, electrical energy is supplied by an engine-

driven alternator. These alternators have advantagesover older style generators as they are lighter inweight, require lower maintenance, and maintain auniform electrical output even at low engine r.p.m.[Figure 5-12]

Turbine powered helicopters use a starter/generatorsystem. The starter/generator is permanently coupledto the engine gearbox. When starting the engine, elec-trical power from the battery is supplied to thestarter/generator, which turns the engine over. Once theengine is running, the starter/generator is driven by theengine and is then used as a generator.

Current from the alternator or generator is deliveredthrough a voltage regulator to a bus bar. The voltageregulator maintains the constant voltage required bythe electrical system by regulating the output of thealternator or generator. An over-voltage control may be

Avionic Bus Bar

Avionic Bus Avionics Relay

On

Off

Avionics Master Switch

Lights

Panel Position Beacon

Trim Instr Lndg Lt

Radio Xpdr Clutch

Ammeter

Mag Switch

Left Magneto

Right Magneto

Starter Relay Engine

Starter

Bus

Bar

Battery Relay

Battery

Battery Switch

Starter Switch

M/R Gearbox Press Switch

Release

Hold

EngageClutch Switch

Alternator

Alternator Switch

Alternator Control Unit

Clutch Actuator (Internal Limit Switches Shown in Full Disengage Position)

24V– +

F1F2

–+

Starting VibratorR

RBoth

L L

OffRet

Adv

Adv

G

(Optional Avionics)

Figure 5-12. An electrical system scematic like this sample isincluded in most POHs. Notice that the various bus baraccessories are protected by circuit breakers. However, youshould still make sure all electrical equipment is turned offbefore you start the engine. This protects sensitive compo-nents, particularly the radios, from damage which may becaused by random voltages generated during the startingprocess.

Filter To Carb

Carb Heat Collector

Manifold Pipe

Door

Filter To Carb

Carb Heat Collector

Manifold Pipe

Door

Heated Air

Carb Heat Off

Carb Heat On

Figure 5-11. When you turn the carburetor heat ON, normalair flow is blocked, and heated air from an alternate sourceflows through the filter to the carburetor.

5-9

incorporated to prevent excessive voltage, which maydamage the electrical components. The bus bar servesto distribute the current to the various electrical com-ponents of the helicopter.

A battery is mainly used for starting the engine. Inaddition, it permits limited operation of electricalcomponents, such as radios and lights, without theengine running. The battery is also a valuable sourceof standby or emergency electrical power in the eventof alternator or generator failure.

An ammeter or loadmeter is used to monitor theelectrical current within the system. The ammeterreflects current flowing to and from the battery. Acharging ammeter indicates that the battery is beingcharged. This is normal after an engine start sincethe battery power used in starting is being replaced.After the battery is charged, the ammeter should sta-bilize near zero since the alternator or generator issupplying the electrical needs of the system. A dis-charging ammeter means the electrical load isexceeding the output of the alternator or generator,and the battery is helping to supply electrical power.This may mean the alternator or generator is mal-functioning, or the electrical load is excessive. Aloadmeter displays the load placed on the alternatoror generator by the electrical equipment. The RFMfor a particular helicopter shows the normal load to

expect. Loss of the alternator or generator causes theloadmeter to indicate zero.

Electrical switches are used to select electrical compo-nents. Power may be supplied directly to the componentor to a relay, which in turn provides power to the component. Relays are used when high current and/orheavy electrical cables are required for a particular com-ponent, which may exceed the capacity of the switch.

Circuit breakers or fuses are used to protect variouselectrical components from overload. A circuit breakerpops out when its respective component is overloaded.The circuit breaker may be reset by pushing it back in,unless a short or the overload still exists. In this case,the circuit breaker continues to pop, indicating an elec-trical malfunction. A fuse simply burns out when it isoverloaded and needs to be replaced. Manufacturersusually provide a holder for spare fuses in the event onehas to be replaced in flight. Caution lights on the instru-ment panel may be installed to show the malfunction ofan electrical component.

HYDRAULICSMost helicopters, other than smaller piston poweredhelicopters, incorporate the use of hydraulic actuatorsto overcome high control forces. [Figure 5-13] A typi-cal hydraulic system consists of actuators, also called

Pressure

Return

Supply

Scupper Drain

Vent Reservoir

Pump

Pressure Regulator Valve

Quick Disconnects

Filter

Solenoid Valve

Servo Actuator, Lateral Cyclic

Servo Actuator, Fore and Aft Cyclic

Servo Actuator, Collective

Pilot Input

Rotor Control

Figure 5-13. A typical hydraulic system for helicopters in the light to medium range is shown here.

5-10

igation capabilities, such as VOR, ILS, and GPSintercept and tracking, which is especially useful inIFR conditions. The most advanced autopilots canfly an instrument approach to a hover without anyadditional pilot input once the initial functions havebeen selected.

The autopilot system consists of electric actuators orservos connected to the flight controls. The number andlocation of these servos depends on the type of systeminstalled. A two-axis autopilot controls the helicopterin pitch and roll; one servo controls fore and aft cyclic,and another controls left and right cyclic. A three-axisautopilot has an additional servo connected to the anti-torque pedals and controls the helicopter in yaw. Afour-axis system uses a fourth servo which controls thecollective. These servos move the respective flight con-trols when they receive control commands from a cen-tral computer. This computer receives data input fromthe flight instruments for attitude reference and fromthe navigation equipment for navigation and trackingreference. An autopilot has a control panel in the cock-pit that allows you to select the desired functions, aswell as engage the autopilot.

For safety purposes, an automatic disengage feature isusually included which automatically disconnects theautopilot in heavy turbulence or when extreme flightattitudes are reached. Even though all autopilots can beoverridden by the pilot, there is also an autopilot disen-gage button located on the cyclic or collective whichallows you to completely disengage the autopilot with-out removing your hands from the controls. Becauseautopilot systems and installations differ from one hel-icopter to another, it is very important that you refer tothe autopilot operating procedures located in theRotorcraft Flight Manual.

ENVIRONMENTAL SYSTEMSHeating and cooling for the helicopter cabin can beprovided in different ways. The simplest form of cool-ing is ram air cooling. Air ducts in the front or sides ofthe helicopter are opened or closed by the pilot to letram air into the cabin. This system is limited as itrequires forward airspeed to provide airflow and also

servos, on each flight control, a pump which is usuallydriven by the main rotor gearbox, and a reservoir tostore the hydraulic fluid. A switch in the cockpit canturn the system off, although it is left on under normalconditions. A pressure indicator in the cockpit may alsobe installed to monitor the system.

When you make a control input, the servo is activatedand provides an assisting force to move the respectiveflight control, thus lightening the force required by thepilot. These boosted flight controls ease pilot workloadand fatigue. In the event of hydraulic system failure,you are still able to control the helicopter, but the con-trol forces will be very heavy.

In those helicopters where the control forces are sohigh that they cannot be moved without hydraulicassistance, two or more independent hydraulic systemsmay be installed. Some helicopters use hydraulic accu-mulators to store pressure, which can be used for ashort period of time in an emergency if the hydraulicpump fails. This gives you enough time to land the hel-icopter with normal control

STABILITY AUGMENTATIONS SYSTEMSSome helicopters incorporate stability augmentationssystems (SAS) to aid in stabilizing the helicopter inflight and in a hover. The simplest of these systems is aforce trim system, which uses a magnetic clutch andsprings to hold the cyclic control in the position whereit was released. More advanced systems use electricservos that actually move the flight controls. Theseservos receive control commands from a computer thatsenses helicopter attitude. Other inputs, such asheading, speed, altitude, and navigation informationmay be supplied to the computer to form a completeautopilot system. The SAS may be overridden ordisconnected by the pilot at any time.

Stability augmentation systems reduce pilot workloadby improving basic aircraft control harmony anddecreasing disturbances. These systems are very usefulwhen you are required to perform other duties, such assling loading and search and rescue operations.

AUTOPILOTHelicopter autopilot systems are similar to stabilityaugmentations systems except they have additionalfeatures. An autopilot can actually fly the helicopterand perform certain functions selected by the pilot.These functions depend on the type of autopilot andsystems installed in the helicopter.

The most common functions are altitude and headinghold. Some more advanced systems include a verticalspeed or indicated airspeed (IAS) hold mode, where aconstant rate of climb/descent or indicated airspeed ismaintained by the autopilot. Some autopilots have nav-

VOR—Ground-based navigation system consisting of very high fre-quency omnidirectional range (VOR) stations which provide courseguidance.

ILS (Instrument Landing System)—A precision instrument approachsystem, which normally consists of the following electronic componentsand visual aids: localizer, glide slope, outer marker, and approachlights.

GPS (Global Positioning System)—A satellite-based radio positioning,navigation, and time-transfer system.

IFR (Instrument Flight Rules)—Rules that govern the procedure forconducting flight in weather conditions below VFR weather minimums.The term IFR also is used to define weather conditions and the type offlight plan under which an aircraft is operating.

5-11

depends on the temperature of the outside air. Air con-ditioning provides better cooling but it is more com-plex and weighs more than a ram air system.

Piston powered helicopters use a heat exchangershroud around the exhaust manifold to provide cabinheat. Outside air is piped to the shroud and the hotexhaust manifold heats the air, which is then blowninto the cockpit. This warm air is heated by the exhaustmanifold but is not exhaust gas. Turbine helicoptersuse a bleed air system for heat. Bleed air is hot, com-pressed, discharge air from the engine compressor. Hotair is ducted from the compressor to the helicoptercabin through a pilot-controlled, bleed air valve.

ANTI-ICING SYSTEMSMost anti-icing equipment installed on small helicoptersis limited to engine intake anti-ice and pitot heat systems.

The anti-icing system found on most turbine-poweredhelicopters uses engine bleed air. The bleed air flowsthrough the inlet guide vanes to prevent ice formation onthe hollow vanes. A pilot-controlled, electrically operatedvalve on the compressor controls the air flow. The pitotheat system uses an electrical element to heat the pitottube, thus melting or preventing ice formation.

Airframe and rotor anti-icing may be found on somelarger helicopters, but it is not common due to the complexity, expense, and weight of such systems. Theleading edges of rotors may be heated with bleed air orelectrical elements to prevent ice formation. Balance andcontrol problems might arise if ice is allowed to formunevenly on the blades. Research is being done on lightweight ice-phobic (anti-icing) materials or coatings.These materials placed in strategic areas could signifi-cantly reduce ice formation and improve performance.

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6-1

Title 14 of the Code of Federal Regulations (14 CFR)part 91 requires that pilots comply with the operatinglimitations specified in approved rotorcraft flight man-uals, markings, and placards. Originally, flight manualswere often characterized by a lack of essential infor-mation and followed whatever format and content themanufacturer felt was appropriate. This changed withthe acceptance of the General Aviation ManufacturersAssociation’s (GAMA) Specification for Pilot’sOperating Handbook, which established a standardizedformat for all general aviation airplane and rotorcraftflight manuals. The term “Pilot’s Operating Handbook(POH)” is often used in place of “Rotorcraft FlightManual (RFM).” However, if “Pilot’s OperatingHandbook” is used as the main title instead of “RotorcraftFlight Manual,” a statement must be included on the titlepage indicating that the document is the FAA-ApprovedRotorcraft Flight Manual. [Figure 6-1]

Besides the preliminary pages, an FAA-ApprovedRotorcraft Flight Manual may contain as many as ten sec-tions. These sections are: General Information; OperatingLimitations; Emergency Procedures; Normal Procedures;Performance; Weight and Balance; Aircraft and SystemsDescription; Handling, Servicing, and Maintenance; andSupplements. Manufacturers have the option of includinga tenth section on Safety and Operational Tips and analphabetical index at the end of the handbook.

PRELIMINARY PAGESWhile rotorcraft flight manuals may appear similar forthe same make and model of aircraft, each flight man-

ual is unique since it contains specific informationabout a particular aircraft, such as the equipmentinstalled, and weight and balance information.Therefore, manufacturers are required to include theserial number and registration on the title page to iden-tify the aircraft to which the flight manual belongs. If aflight manual does not indicate a specific aircraft regis-tration and serial number, it is limited to general studypurposes only.

Most manufacturers include a table of contents, whichidentifies the order of the entire manual by section num-ber and title. Usually, each section also contains its owntable of contents. Page numbers reflect the section youare reading, 1-1, 2-1, 3-1, and so on. If the flight manualis published in looseleaf form, each section is usuallymarked with a divider tab indicating the section numberor title, or both. The Emergency Procedures section mayhave a red tab for quick identification and reference.

GENERAL INFORMATIONThe General Information section provides the basicdescriptive information on the rotorcraft and the power-plant. In some manuals there is a three-view drawing ofthe rotorcraft that provides the dimensions of variouscomponents, including the overall length and width, andthe diameter of the rotor systems. This is a good place toquickly familiarize yourself with the aircraft.

You can find definitions, abbreviations, explanations ofsymbology, and some of the terminology used in themanual at the end of this section. At the option of themanufacturer, metric and other conversion tables mayalso be included.

OPERATING LIMITATIONSThe Operating Limitations section contains only thoselimitations required by regulation or that are necessaryfor the safe operation of the rotorcraft, powerplant, sys-tems, and equipment. It includes operating limitations,instrument markings, color coding, and basic placards.Some of the areas included are: airspeed, altitude, rotor,and powerplant limitations, including fuel and oilrequirements; weight and loading distribution; andflight limitations.

AIRSPEED LIMITATIONSAirspeed limitations are shown on the airspeed indica-tor by color coding and on placards or graphs in the

Figure 6-1. The Rotorcraft Flight Manual is a regulatory docu-ment in terms of the maneuvers, procedures, and operatinglimitations described therein.

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aircraft. A red line on the airspeed indicator shows theairspeed limit beyond which structural damage couldoccur. This is called the never exceed speed, or VNE.The normal operating speed range is depicted by a greenarc. A blue line is sometimes added to show the maxi-mum safe autorotation speed. [Figure 6-2]

ALTITUDE LIMITATIONSIf the rotorcraft has a maximum operating density alti-tude, it is indicated in this section of the flight manual.Sometimes the maximum altitude varies based on differ-ent gross weights.

ROTOR LIMITATIONSLow rotor r.p.m. does not produce sufficient lift, andhigh r.p.m. may cause structural damage, thereforerotor r.p.m. limitations have minimum and maximumvalues. A green arc depicts the normal operating rangewith red lines showing the minimum and maximumlimits. [Figure 6-3]

There are two different rotor r.p.m. limitations: power-onand power-off. Power-on limitations apply anytime theengine is turning the rotor and is depicted by a fairly nar-row green band. A yellow arc may be included to show atransition range, which means that operation within thisrange is limited. Power-off limitations apply anytime theengine is not turning the rotor, such as when in an autoro-tation. In this case, the green arc is wider than the power-on arc, indicating a larger operating range.

POWERPLANT LIMITATIONSThe Powerplant Limitations area describes operatinglimitations on the rotorcraft’s engine including suchitems as r.p.m. range, power limitations, operating tem-peratures, and fuel and oil requirements. Most turbineengines and some reciprocating engines have a maxi-mum power and a maximum continuous power rating.The “maximum power” rating is the maximum powerthe engine can generate and is usually limited by time.The maximum power range is depicted by a yellow arcon the engine power instruments, with a red line indi-cating the maximum power that must not be exceeded.“Maximum continuous power” is the maximum powerthe engine can generate continually, and is depicted bya green arc. [Figure 6-4]

Like on a torque and turbine outlet temperature gauge,the red line on a manifold pressure gauge indicates themaximum amount of power. A yellow arc on the gaugewarns of pressures approaching the limit of ratedpower. A placard near the gauge lists the maximumreadings for specific conditions. [Figure 6-5]

WEIGHT AND LOADING DISTRIBUTIONThe Weight and Loading Distribution area contains themaximum certificated weights, as well as the center ofgravity (CG) range. The location of the reference datumused in balance computations should also be included inthis section. Weight and balance computations are notprovided here, but rather in the Weight and BalanceSection of the FAA-Approved Rotocraft Flight Manual.

150 20

40

60

80

100

120AIRSPEED

KNOTS

17

14

128

6

4

MPHX 10

Figure 6-2. Typical airspeed indicator limitations and mark-ings.

ROTOR

ENGINE

R P M100

5

l0

l

23

4

5

l520

25

30

35

40

Figure 6-3. Markings on a typical dual-needle tachometer in areciprocating-engine helicopter. The outer band shows thelimits of the superimposed needles when the engine is turn-ing the rotor. The inner band indicates the power-off limits.

4050 60 70

8090

100

1101200

1020

30TORQUE

PERCENT

12

34 5

6

7

89

TURBOUT

TEMP°C X 100

Figure 6-4. Torque and turbine outlet temperature (TOT)gauges are commonly used with turbine-powered aircraft.

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FLIGHT LIMITATIONSThis area lists any maneuvers which are prohibited,such as acrobatic flight or flight into known icing con-ditions. If the rotorcraft can only be flown in VFRconditions, it will be noted in this area. Also includedare the minimum crew requirements, and the pilot seatlocation, if applicable, where solo flights must be con-ducted.

PLACARDSAll rotorcraft generally have one or more placards dis-played that have a direct and important bearing on thesafe operation of the rotorcraft. These placards arelocated in a conspicuous place within the cabin andnormally appear in the Limitations Section. Since VNEchanges with altitude, this placard can be found in allhelicopters. [Figure 6-6]

EMERGENCY PROCEDURESConcise checklists describing the recommended proce-dures and airspeeds for coping with various types ofemergencies or critical situations can be found in thissection. Some of the emergencies covered include:engine failure in a hover and at altitude, tail rotor fail-ures, fires, and systems failures. The procedures forrestarting an engine and for ditching in the water mightalso be included.

Manufacturers may first show the emergencies check-lists in an abbreviated form with the order of itemsreflecting the sequence of action. This is followed byamplified checklists providing additional informationto help you understand the procedure. To be preparedfor an abnormal or emergency situation, memorize thefirst steps of each checklist, if not all the steps. If timepermits, you can then refer to the checklist to make sureall items have been covered. (For more information onemergencies, refer to Chapter 11—Helicopter Emergenciesand Chapter 21—Gyroplane Emergencies.)

Manufacturers also are encouraged to include an optionalarea titled “Abnormal Procedures,” which describes rec-ommended procedures for handling malfunctions that arenot considered to be emergencies. This informationwould most likely be found in larger helicopters.

NORMAL PROCEDURESThe Normal Procedures is the section you will proba-bly use the most. It usually begins with a listing of theairspeeds, which may enhance the safety of normaloperations. It is a good idea to memorize the airspeedsthat are used for normal flight operations. The next partof the section includes several checklists, which takeyou through the preflight inspection, before startingprocedure, how to start the engine, rotor engagement,ground checks, takeoff, approach, landing, and shut-down. Some manufacturers also include the proceduresfor practice autorotations. To avoid skipping an impor-tant step, you should always use a checklist when one isavailable. (More information on maneuvers can befound in Chapter 9—Basic Maneuvers, Chapter 10—Advanced Maneuvers, and Chapter 20—GyroplaneFlight Operations.)

PERFORMANCEThe Performance Section contains all the informationrequired by the regulations, and any additional per-formance information the manufacturer feels mayenhance your ability to safely operate the rotorcraft.

l5

l0

2025

355

30MANIFOLDPRESSURE

INCHESOF MERCURY

Figure 6-5. A manifold pressure gauge is commonly usedwith piston-powered aircraft.

Press Alt.1,000 FTF OAT 8 4 6 8 10 12 14

0 109 109 105 84 61 -- --

109 109 109 109 98 77 58109 109 109 109 85 67 48109 109 109 96 75 57 --109 109 108 84 66 48 --109 109 95 74 57 -- --109 108 84 66 48 -- --

109 109 94 72 49 -- --09 103 81 59 -- -- --

109 91 70 48 -- -- --109 80 59 -- -- -- --109 70 48 -- -- -- --

20406080

100

020406080

100

MAXIMUM VNE DOORS OFF - 102 MPH IAS

VNE - MPH IASGROSS WEIGHT

MORE THAN 1,700 LBS

1,700 LBS OR

LESS

NEVER EXCEED SPEED

Pressure Al t . 1,000 Feet0 2 4 6 8 10 12 14

110

100

90

80

70

60

50

KIAS

VNE -20° C

0° C+20° C+40° C

MAX ALT.

Figure 6-6. Various VNE placards.

ers should describe the systems in a manner that isunderstandable to most pilots. For larger, more com-plex rotorcraft, the manufacturer may assume a higherdegree of knowledge. (For more information on rotor-craft systems, refer to Chapter 5—Helicopter Systemsand Chapter 18—Gyroplane Systems.)

HANDLING, SERVICING, ANDMAINTENANCEThe Handling, Servicing, and Maintenance sectiondescribes the maintenance and inspections recom-mended by the manufacturer, as well as those requiredby the regulations, and Airworthiness Directive (AD)compliance procedures. There are also suggestions onhow the pilot/operator can ensure that the work is doneproperly.

This section also describes preventative maintenancethat may be accomplished by certificated pilots, aswell as the manufacturer’s recommended ground han-dling procedures, including considerations forhangaring, tie down, and general storage proceduresfor the rotorcraft.

SUPPLEMENTSThe Supplements Section describes pertinent informa-tion necessary to operate optional equipment installed onthe rotorcraft that would not be installed on a standardaircraft. Some of this information may be supplied by theaircraft manufacturer, or by the maker of the optionalequipment. The information is then inserted into theflight manual at the time the equipment is installed.

SAFETY AND OPERATIONAL TIPSThe Safety and Operational Tips is an optional sectionthat contains a review of information that couldenhance the safety of the operation. Some examples ofthe information that might be covered include: physio-logical factors, general weather information, fuel con-servation procedures, external load warnings, low rotorr.p.m. considerations, and recommendations that if notadhered to could lead to an emergency.

Airworthiness Directive (AD)—Aregulatory notice that is sent outby the FAA to the registered own-ers of aircraft informing them ofthe discovery of a condition thatkeeps their aircraft from continu-ing to meet its conditions for air-worthiness. AirworthinessDirectives must be complied withwithin the required time limit, andthe fact of compliance, the date ofcompliance, and the method ofcompliance must be recorded inthe aircraft maintenance records.

6-4

These charts, graphs, and tables vary in style but allcontain the same basic information. Some examplesof the performance information that can be found inmost flight manuals include a calibrated versus indi-cated airspeed conversion graph, hovering ceilingversus gross weight charts, and a height-velocity dia-gram. [Figure 6-7] For information on how to use thecharts, graphs, and tables, refer to Chapter 8—Performance.

WEIGHT AND BALANCEThe Weight and Balance section should contain all theinformation required by the FAA that is necessary tocalculate weight and balance. To help you correctlycompute the proper data, most manufacturers includesample problems. (Weight and balance is further dis-cussed in Chapter 7—Weight and Balance.)

AIRCRAFT AND SYSTEMSDESCRIPTIONThe Aircraft and Systems Description section is anexcellent place to study and familiarize yourself withall the systems found on your aircraft. The manufactur-

1,5001,4000

2,000

4,000

6,000

8,000

10,000

12,000

1,600 1,700 1,800

PR

ES

SU

RE

ALT

ITU

DE

~F

EE

T

GROSS WEIGHT ~ LBS

8,000 FT. DENSITY ALTITUDE

MIXTURE FULL RICH

OAT 120°F

OAT 100°F

OAT 80°F

OAT 60°F

OAT 40°F

OAT 20°F

OAT 0°F

Figure 6-7. One of the performance charts in the PerformanceSection is the “In Ground Effect Hover Ceiling versus GrossWeight” chart. This chart allows you to determine how muchweight you can carry and still operate at a specific pressurealtitude, or if you are carrying a specific weight, what is youraltitude limitation.

7-1

It is vital to comply with weight and balance limitsestablished for helicopters. Operating above the maxi-mum weight limitation compromises the structuralintegrity of the helicopter and adversely affects per-formance. Balance is also critical because on somefully loaded helicopters, center of gravity deviations assmall as three inches can dramatically change a heli-copter’s handling characteristics. Taking off in a heli-copter that is not within the weight and balancelimitations is unsafe.

WEIGHTWhen determining if your helicopter is within theweight limits, you must consider the weight of the basichelicopter, crew, passengers, cargo, and fuel. Althoughthe effective weight (load factor) varies during maneu-vering flight, this chapter primarily considers theweight of the loaded helicopter while at rest.

The following terms are used when computing a heli-copter’s weight.

BASIC EMPTY WEIGHT—The starting point forweight computations is the basic empty weight, whichis the weight of the standard helicopter, optionalequipment, unusable fuel, and full operating fluidsincluding full engine oil. Some helicopters might usethe term “licensed empty weight,” which is nearly thesame as basic empty weight, except that it does notinclude full engine oil, just undrainable oil. If you fly ahelicopter that lists a licensed empty weight, be sure toadd the weight of the oil to your computations.

USEFUL LOAD—The difference between the grossweight and the basic empty weight is referred to asuseful load. It includes the flight crew, usable fuel,drainable oil, if applicable, and payload.

PAYLOAD—The weight of the passengers, cargo, andbaggage.

GROSS WEIGHT—The sum of the basic empty weightand useful load.

MAXIMUM GROSS WEIGHT— The maximumweight of the helicopter. Most helicopters have an inter-nal maximum gross weight, which refers to the weightwithin the helicopter structure and an external maximumgross weight, which refers to the weight of the helicopterwith an external load.

WEIGHT LIMITATIONSWeight limitations are necessary to guarantee the struc-tural integrity of the helicopter, as well as enabling youto predict helicopter performance accurately. Althoughaircraft manufacturers build in safety factors, youshould never intentionally exceed the load limits forwhich a helicopter is certificated. Operating above amaximum weight could result in structural deformationor failure during flight if you encounter excessive loadfactors, strong wind gusts, or turbulence. Operatingbelow a minimum weight could adversely affect thehandling characteristics of the helicopter. During sin-gle-pilot operations in some helicopters, you may haveto use a large amount of forward cyclic in order tomaintain a hover. By adding ballast to the helicopter,the cyclic will be closer to the center, which gives youa greater range of control motion in every direction.Additional weight also improves autorotational charac-teristics since the autorotational descent can be estab-lished sooner. In addition, operating below minimumweight could prevent you from achieving the desirablerotor r.p.m. during autorotations.

Although a helicopter is certificated for a specifiedmaximum gross weight, it is not safe to take off withthis load under all conditions. Anything that adverselyaffects takeoff, climb, hovering, and landing perform-ance may require off-loading of fuel, passengers, orbaggage to some weight less than the published maxi-mum. Factors which can affect performance includehigh altitude, high temperature, and high humidity con-ditions, which result in a high density altitude.

DETERMINING EMPTY WEIGHTA helicopter’s weight and balance records containessential data, including a complete list of all installedoptional equipment. Use these records to determine theweight and balance condition of the empty helicopter.

When a helicopter is delivered from the factory, the basicempty weight, empty weight center of gravity (CG), anduseful load are recorded on a weight and balance datasheet included in the FAA-Approved Rotocraft FlightManual. The basic empty weight can vary even in thesame model of helicopter because of differences ininstalled equipment. If the owner or operator of a heli-copter has equipment removed, replaced, or additionalequipment installed, these changes must be reflected inthe weight and balance records. In addition, major

7-2

repairs or alterations must be recorded by a certifiedmechanic. When the revised weight and moment arerecorded on a new form, the old record is marked withthe word “superseded” and dated with the effectivedate of the new record. This makes it easy to determinewhich weight and balance form is the latest version.You must use the latest weight and balance data forcomputing all loading problems.

BALANCEHelicopter performance is not only affected by grossweight, but also by the position of that weight. It isessential to load the aircraft within the allowable center-of-gravity range specified in the rotorcraft flight man-ual’s weight and balance limitations.

CENTER OF GRAVITY (CG)The center of gravity is defined as the theoretical pointwhere all of the aircraft’s weight is considered to beconcentrated. If a helicopter was suspended by a cableattached to the center-of-gravity point, it would balancelike a teeter-totter. For helicopters with a single mainrotor, the CG is usually close to the main rotor mast.

Improper balance of a helicopter’s load can result inserious control problems. The allowable range in whichthe CG may fall is called the “CG range.” The exactCG location and range are specified in the rotorcraftflight manual for each helicopter. In addition to makinga helicopter difficult to control, an out-of-balance load-ing condition also decreases maneuverability sincecyclic control is less effective in the direction oppositeto the CG location.

Ideally, you should try to perfectly balance a helicopterso that the fuselage remains horizontal in hoveringflight, with no cyclic pitch control needed except forwind correction. Since the fuselage acts as a pendulumsuspended from the rotor, changing the center of grav-ity changes the angle at which the aircraft hangs fromthe rotor. When the center of gravity is directly underthe rotor mast, the helicopter hangs horizontal; if theCG is too far forward of the mast, the helicopter hangswith its nose tilted down; if the CG is too far aft of themast, the nose tilts up. [Figure 7-1]

CG FORWARD OF FORWARD LIMITA forward CG may occur when a heavy pilot and pas-senger take off without baggage or proper ballastlocated aft of the rotor mast. This situation becomesworse if the fuel tanks are located aft of the rotor mastbecause as fuel burns the weight located aft of the rotormast becomes less.

You can recognize this condition when coming to ahover following a vertical takeoff. The helicopter willhave a nose-low attitude, and you will need excessiverearward displacement of the cyclic control to maintaina hover in a no-wind condition. You should not continueflight in this condition, since you could rapidly run outof rearward cyclic control as you consume fuel. You alsomay find it impossible to decelerate sufficiently to bringthe helicopter to a stop. In the event of engine failure andthe resulting autorotation, you may not have enoughcyclic control to flare properly for the landing.

A forward CG will not be as obvious when hovering intoa strong wind, since less rearward cyclic displacement isrequired than when hovering with no wind. When deter-mining whether a critical balance condition exists, it isessential to consider the wind velocity and its relation tothe rearward displacement of the cyclic control.

CG AFT OF AFT LIMITWithout proper ballast in the cockpit, exceeding the aftCG may occur when:

• A lightweight pilot takes off solo with a full loadof fuel located aft of the rotor mast.

• A lightweight pilot takes off with maximum bag-gage allowed in a baggage compartment locatedaft of the rotor mast.

• A lightweight pilot takes off with a combinationof baggage and substantial fuel where both are aftof the rotor mast.

You can recognize the aft CG condition when comingto a hover following a vertical takeoff. The helicopterwill have a tail-low attitude, and you will need exces-

Forward CG

CG Directly Under The Rotor Mast

Aft CG

Figure 7-1. The location of the center of gravity strongly influences how the helicopter handles.

7-3

sive forward displacement of cyclic control to main-tain a hover in a no-wind condition. If there is a wind,you need even greater forward cyclic.

If flight is continued in this condition, you may find itimpossible to fly in the upper allowable airspeed rangedue to inadequate forward cyclic authority to maintain anose-low attitude. In addition, with an extreme aft CG,gusty or rough air could accelerate the helicopter to aspeed faster than that produced with full forward cycliccontrol. In this case, dissymmetry of lift and blade flap-ping could cause the rotor disc to tilt aft. With full for-ward cyclic control already applied, you might not beable to lower the rotor disc, resulting in possible loss ofcontrol, or the rotor blades striking the tailboom.

LATERAL BALANCEFor most helicopters, it is usually not necessary todetermine the lateral CG for normal flight instructionand passenger flights. This is because helicopter cab-ins are relatively narrow and most optional equip-ment is located near the center line. However, somehelicopter manuals specify the seat from which youmust conduct solo flight. In addition, if there is anunusual situation, such as a heavy pilot and a fullload of fuel on one side of the helicopter, which couldaffect the lateral CG, its position should be checkedagainst the CG envelope. If carrying external loads ina position that requires large lateral cyclic controldisplacement to maintain level flight, fore and aftcyclic effectiveness could be dramatically limited.

WEIGHT AND BALANCECALCULATIONSWhen determining whether your helicopter is properlyloaded, you must answer two questions:

1. Is the gross weight less than or equal to the max-imum allowable gross weight?

2. Is the center of gravity within the allowable CGrange, and will it stay within the allowable rangeas fuel is burned off?

To answer the first question, just add the weight of theitems comprising the useful load (pilot, passengers,fuel, oil, if applicable, cargo, and baggage) to the basicempty weight of the helicopter. Check that the total weightdoes not exceed the maximum allowable gross weight.

To answer the second question, you need to use CG ormoment information from loading charts, tables, or graphsin the rotorcraft flight manual. Then using one of themethods described below, calculate the loaded momentand/or loaded CG and verify that it falls within the allow-able CG range shown in the rotorcraft flight manual.

It is important to note that any weight and balance com-putation is only as accurate as the information provided.Therefore, you should ask passengers what they weigh

and add a few pounds to cover the additional weight ofclothing, especially during the winter months. The bag-gage weight should be determined by the use of a scale, ifpractical. If a scale is not available, be conservative andoverestimate the weight. Figure 7-2 indicates the stan-dard weights for specific operating fluids.

The following terms are used when computing a heli-copter’s balance.

REFERENCE DATUM—Balance is determined by thelocation of the CG, which is usually described as agiven number of inches from the reference datum. Thehorizontal reference datum is an imaginary verticalplane or point, arbitrarily fixed somewhere along thelongitudinal axis of the helicopter, from which all hori-zontal distances are measured for weight and balancepurposes. There is no fixed rule for its location. It maybe located at the rotor mast, the nose of the helicopter,or even at a point in space ahead of the helicopter.[Figure 7-3]

Aviation Gasoline (AVGAS) . . . . . . . . . . . . . . . . . . .6 lbs. / gal.

Jet Fuel (JP-4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 lbs. / gal.

Jet Fuel (JP-5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8 lbs. / gal.

Reciprocating Engine Oil . . . . . . . . . . . . . . . . . . 7.5 lbs. / gal.*

Turbine Engine Oil . . Varies between 7.5 and 8.5 lbs. / gal.*

Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.35 lbs. / gal. * Oil weight is given in pounds per gallon while oil capacity is usually given in quarts; therefore, you must convert the amount of oil to gallons before calculating its weight.

Figure 7-2. When making weight and balance computations,always use actual weights if they are available, especially ifthe helicopter is loaded near the weight and balance limits.

Datum +–

Figure 7-3. While the horizontal reference datum can be any-where the manufacturer chooses, most small training heli-copters have the horizontal reference datum 100 inchesforward of the main rotor shaft centerline. This is to keep allthe computed values positive.

7-4

The lateral reference datum, is usually located at thecenter of the helicopter. The location of the referencedatums is established by the manufacturer and isdefined in the rotorcraft flight manual. [Figure 7-4]

ARM—The horizontal distance from the datum to anycomponent of the helicopter or to any object locatedwithin the helicopter is called the arm. Another termthat can be used interchangeably with arm is station.If the component or object is located to the rear of thedatum, it is measured as a positive number and usu-ally is referred to as inches aft of the datum.Conversely, if the component or object is located for-ward of the datum, it is indicated as a negative num-ber and is usually referred to as inches forward of thedatum.

MOMENT—If the weight of an object is multiplied byits arm, the result is known as its moment. You maythink of moment as a force that results from an object’sweight acting at a distance. Moment is also referred toas the tendency of an object to rotate or pivot about apoint. The farther an object is from a pivotal point, thegreater its force.

CENTER OF GRAVITY COMPUTATION—By totaling theweights and moments of all components and objects car-ried, you can determine the point where a loaded heli-copter would balance. This point is known as the centerof gravity.

WEIGHT AND BALANCE METHODSSince weight and balance is so critical to the safe oper-ation of a helicopter, it is important to know how tocheck this condition for each loading arrangement.Most helicopter manufacturers use one of two meth-ods, or a combination of the methods, to check weightand balance conditions.

COMPUTATIONAL METHODWith the computational method, you use simple math-ematics to solve weight and balance problems. The firststep is to look up the basic empty weight and totalmoment for the particular helicopter you fly. If the cen-ter of gravity is given, it should also be noted. Theempty weight CG can be considered the arm of theempty helicopter. This should be the first item recordedon the weight and balance form. [Figure 7-5]

Next, the weights of the oil, if required, pilot, passen-gers, baggage, and fuel are recorded. Use care inrecording the weight of each passenger and baggage.Recording each weight in its proper location isextremely important to the accurate calculation of aCG. Once you have recorded all of the weights, addthem together to determine the total weight of theloaded helicopter.

Now, check to see that the total weight does not exceedthe maximum allowable weight under existing condi-tions. In this case, the total weight of the helicopter isunder the maximum gross weight of 3,200 pounds.

Figure 7-4. The lateral reference datum is located longitudi-nally through the center of the helicopter; therefore, there arepositive and negative values.

Weight Arm Moment (pounds) (inches) (lb/inches)

Basic Empty Weight

Oil

Pilot

Forward Passenger

Passengers Aft

Baggage

Fuel

Total

CG

1,700

12

190

170

510

40

553

3,175

116.5

179.0

65.0

65.0

104

148

120

109.9

198,050

2,148

12,350

11,050

53,040

5,920

66,360

348,918

Max Gross Weight = 3,200 lbs. CG Range 106.0 – 114.2 in.

Figure 7-5. In this example, the helicopter’s weight of 1,700pounds is recorded in the first column, its CG or arm of 116.5inches in the second, and its moment of 198,050 pound-inches in the last. Notice that the weight of the helicopter,multiplied by its CG, equals its moment.

Lateral Datum

+ –

+ –

Front View

Top View

7-5

Once you are satisfied that the total weight is withinprescribed limits, multiply each individual weight byits associated arm to determine its moment. Then, addthe moments together to arrive at the total moment forthe helicopter. Your final computation is to find thecenter of gravity of the loaded helicopter by dividingthe total moment by the total weight.

After determining the helicopter’s weight and centerof gravity location, you need to determine if the CGis within acceptable limits. In this example, theallowable range is between 106.0 inches and 114.2inches. Therefore, the CG location is within theacceptable range. If the CG falls outside the accept-able limits, you will have to adjust the loading of thehelicopter.

LOADING CHART METHODYou can determine if a helicopter is within weight andCG limits using a loading chart similar to the one infigure 7-6. To use this chart, first subtotal the emptyweight, pilot, and passengers. This is the weight atwhich you enter the chart on the left. The next step is tofollow the upsloping lines for baggage and then for fuelto arrive at your final weight and CG. Any value on orinside the envelope is within the range.

SAMPLE PROBLEM 1Determine if the gross weight and center of gravity arewithin allowable limits under the following loadingconditions for a helicopter based on the loading chartin figure 7-6.

To use the loading chart for the helicopter in this exam-ple, you must add up the items in a certain order. Themaximum allowable gross weight is 1,600 pounds.

ITEM POUNDSBasic empty weight 1,040Pilot 135Passenger 200Subtotal 1,375 (point A)Baggage compartment load 25Subtotal 1,400 (point B)Fuel load (30 gallons) 180Total weight 1,580 (point C)

1. Follow the green arrows in figure 7-6. Enter thegraph on the left side at 1,375 lb., the subtotal ofthe empty weight and the passenger weight.Move right to the yellow line. (point A)

2. Move up and to the right, parallel to the baggagecompartment loading lines to 1,400 lb. (Point B)

3. Continue up and to the right, this time parallel tothe fuel loading lines, to the total weight of 1,580lb. (Point C).

Point C is within allowable weight and CG limits.

SAMPLE PROBLEM 2Assume that the pilot in sample problem 1 dischargesthe passenger after using only 20 pounds of fuel.

ITEM POUNDSBasic empty weight 1,040Pilot 135Subtotal 1,175 (point D)Baggage compartment load 25Subtotal 1,200 (point E)Fuel load 160Total weight 1,360 (point F)

Follow the blue arrows in figure 7-6, starting at 1,175lb. on the left side of the graph, then to point D, E, andF. Although the total weight of the helicopter is wellbelow the maximum allowable gross weight, point Ffalls outside the aft allowable CG limit.

As you can see, it is important to reevaluate the balancein a helicopter whenever you change the loading. Unlikemost airplanes, where discharging a passenger isunlikely to adversely affect the CG, off-loading a pas-senger from a helicopter could make the aircraft unsafeto fly. Another difference between helicopter and air-plane loading is that most small airplanes carry fuel inthe wings very near the center of gravity. Burning offfuel has little effect on the loaded CG. However, heli-copter fuel tanks are often significantly behind the centerof gravity. Consuming fuel from a tank aft of the rotormast causes the loaded helicopter CG to move forward.As standard practice, you should compute the weightand balance with zero fuel to verify that your helicopterremains within the acceptable limits as fuel is used.

A B

C

D

F

1,600 1,500 1,400 1,300 1,200 1,100

104 105 106 107 108 109

Baggage Compartment Loading Lines

Fuel Loading Lines

E

Figure 7-6. Loading chart illustrating the solution to sampleproblems 1 and 2.

7-6

SAMPLE PROBLEM 3The loading chart used in the sample problems 1 and 2is designed to graphically calculate the loaded center ofgravity and show whether it is within limits, all on asingle chart. Another type of loading chart calculatesmoments for each station. You must then add up thesemoments and consult another graph to determinewhether the total is within limits. Although this methodhas more steps, the charts are sometimes easier to use.

To begin, record the basic empty weight of the helicop-ter, along with its total moment. Remember to use theactual weight and moment of the helicopter you are fly-ing. Next, record the weights of the pilot, passengers,fuel, and baggage on a weight and balance worksheet.Then, determine the total weight of the helicopter.Once you have determined the weight to be within pre-scribed limits, compute the moment for each weightand for the loaded helicopter. Do this with a loadinggraph provided by the manufacturer. Use figure 7-7 todetermine the moments for a pilot and passengerweighing 340 pounds and for 211 pounds of fuel.

Start at the bottom scale labeled LOAD WEIGHT.Draw a line from 211 pounds up to the line labeled“FUEL @ STA108.5.” Draw your line to the left tointersect the MOMENT scale and read the fuel moment(22.9 thousand lb.-inches). Do the same for the pilot/pas-senger moment. Draw a line from a weight of 340pounds up to the line labeled “PILOT & PASSENGER

@STA. 83.2.” Go left and read the pilot/passengermoment (28.3 thousand lb.-inches).

Reduction factors are often used to reduce the size oflarge numbers to manageable levels. In figure 7-7, thescale on the loading graph gives you moments in thou-sands of pound-inches. In most cases, when using thistype of chart, you need not be concerned with reduc-tion factors because the CG/moment envelope chartnormally uses the same reduction factor. [Figure 7-8]

After recording the basic empty weight and moment ofthe helicopter, and the weight and moment for eachitem, total and record all weights and moments. Next,plot the calculated takeoff weight and moment on thesample moment envelope graph. Based on a weight of1,653 pounds and a moment/1,000 of 162 pound-inches,the helicopter is within the prescribed CG limits.

COMBINATION METHODThe combination method usually uses the computa-tion method to determine the moments and center ofgravity. Then, these figures are plotted on a graph todetermine if they intersect within the acceptable enve-lope. Figure 7-9 illustrates that with a total weight of2,399 pounds and a total moment of 225,022 pound-

FUE

L@

STA

. 108

.5

PIL

OT

&PA

SS

EN

GE

R@

STA

. 83.

2

0100 200 300 400 500

4

8

12

16

20

24

28

32

36

MO

ME

NT

(TH

OU

SA

ND

SO

FLB

S.-

IN.)

LOAD WEIGHT (LBS)

Figure 7-7. Moments for fuel, pilot, and passenger.

190

180

170

160

150

140

130

120

110

1001,100 1,200 1,300 1,400 1,500

1,600 1,700

LOADED WEIGHT (POUND)

LOA

DM

OM

EN

T/1

000

(PO

UN

DS

-IN

CH

ES

)

1. Basic Empty Weight..................

2. Pilot and Front Passenger........

3. Fuel...........................................

5. Baggage...................................

TOTALS

Weight (lbs.)

Moment (lb.-ins. /1,000)

1,102 110.8

28.3340

22.9211

162.01,653

Aft CG Limit Station 101.0

Forward CG Limit Station 95.0

Figure 7-8. CG/Moment Chart.

7-7

inches, the CG is 93.8. Plotting this CG against theweight indicates that the helicopter is loaded withinthe longitudinal limits (point A).

CALCULATING LATERAL CGSome helicopter manufacturers require that you alsodetermine the lateral CG limits. These calculations aresimilar to longitudinal calculations. However, since thelateral CG datum line is almost always defined as thecenter of the helicopter, you are likely to encounternegative CGs and moments in your calculations.Negative values are located on the left side while posi-tive stations are located on the right.

Refer to figure 7-10. When computing moment for thepilot, 170 pounds is multiplied by the arm of 12.2 inchesresulting in a moment of 2,074 pound-inches. As withany weight placed right of the aircraft centerline, themoment is expressed as a positive value. The forwardpassenger sits left of the aircraft centerline. To computethis moment, multiply 250 pounds by –10.4 inches. Theresult is in a moment of –2,600 pound-inches. Once theaircraft is completely loaded, the weights and momentsare totaled and the CG is computed. Since more weightis located left of the aircraft centerline, the resultingtotal moment is –3,837 pound-inches. To calculate CG,divide –3,837 pound-inches by the total weight of 2,399pounds. The result is –1.6 inches, or a CG that is 1.6inches left of the aircraft centerline.

Weight Arm Moment (pounds) (inches) (lb/inches)

Basic Empty Weight

Pilot

Fwd Passenger

Right Fwd Baggage

Left Fwd Baggage

Right Aft Passenger

Left Aft Passenger

Right Aft Baggage

Left Aft Baggage

Totals with Zero Fuel

Main Fuel Tank

Aux Fuel Tank

Totals with Fuel

CG

1,400

170

250

185

50

50

2,105

184

110

2,399

107.75

49.5

49.5

44

44

79.5

79.5

79.5

79.5

106

102

93.8

150,850

8,415

12,375

0

0

0

14,708

3,975

3,975

194,298

19,504

11,220

225,022

Longitudinal

2,500

2,300

2,100

1,900

1,700

1,500

CL

91 93 95 97 99 101 103

260

256

252

248

244

240

236

232

1,100 1,050 1,000 950 900 850 800 750 700

Fuselage Station (CM from Datum)

Gro

ssW

eigh

t-lb

.

Gro

ssW

eigh

t-K

G

Fuselage Station (in. from Datum)

Main Rotor

Most Fwd CG with Full Fuel

Longitudinal

(Point A)

Figure 7-9. Use the longitudinal CG envelope along with the computed CGs to determine if the helicopter is loaded properly.

Figure 7-10. Computed Lateral CG.

Weight Arm Moment (pounds) (inches) (lb/inches)

Basic Empty Weight

Pilot

Fwd Passenger

Right Fwd Baggage

Left Fwd Baggage

Right Aft Passenger

Left Aft Passenger

Right Aft Baggage

Left Aft Baggage

Totals with Zero Fuel

Main Fuel Tank

Aux Fuel Tank

Totals with Fuel

CG

1,400

170

250

185

50

50

2,105

184

110

2,399

0

12.2

–10.4

11.5

–11.5

12.2

–12.2

12.2

–12.2

–13.5

13

–1.6

0

2,074

–2,600

0

0

0

–2,257

610

–610

–2,783

–2,484

1,430

–3,837

Lateral

7-8

Lateral CG is often plotted against the longitudinal CG.[Figure 7-11] In this case, –1.6 is plotted against 93.8,which was the longitudinal CG determined in the previ-ous problem. The intersection of the two lines falls wellwithin the lateral CG envelope.

CL

260

256

252

248

244

240

236

232

8R 6R 4R 2R 02L 4L 6L 8L

Fuselage Station (CM from Datum)

Late

ral-

in.

Late

ralC

G-

CM

Fuselage Station (in. from Datum)Lateral

3R

1R

1L

3L

CLMain Rotor

(Point A)

91 93 95 97 99 101 103

Figure 7-11. Use the lateral CG envelope to determine if thehelicopter is properly loaded.

8-1

Your ability to predict the performance of a helicopteris extremely important. It allows you to determinehow much weight the helicopter can carry beforetakeoff, if your helicopter can safely hover at a spe-cific altitude and temperature, how far it will take toclimb above obstacles, and what your maximumclimb rate will be.

FACTORS AFFECTING PERFORMANCEA helicopter’s performance is dependent on the poweroutput of the engine and the lift production of therotors, whether it is the main rotor(s) or tail rotor. Anyfactor that affects engine and rotor efficiency affectsperformance. The three major factors that affect per-formance are density altitude, weight, and wind.

DENSITY ALTITUDEThe density of the air directly affects the performanceof the helicopter. As the density of the air increases,engine power output, rotor efficiency, and aerodynamiclift all increase. Density altitude is the altitude abovemean sea level at which a given atmospheric densityoccurs in the standard atmosphere. It can also beinterpreted as pressure altitude corrected for nonstan-dard temperature differences.

Pressure altitude is displayed as the height above astandard datum plane, which, in this case, is a theoret-ical plane where air pressure is equal to 29.92 in. Hg.Pressure altitude is the indicated height value on thealtimeter when the altimeter setting is adjusted to29.92 in. Hg. Pressure altitude, as opposed to true alti-tude, is an important value for calculating perform-ance as it more accurately represents the air content ata particular level. The difference between true altitude

and pressure altitude must be clearly understood. Truealtitude means the vertical height above mean sea leveland is displayed on the altimeter when the altimeter iscorrectly adjusted to the local setting.

For example, if the local altimeter setting is 30.12 in.Hg., and the altimeter is adjusted to this value, thealtimeter indicates exact height above sea level.However, this does not reflect conditions found at thisheight under standard conditions. Since the altimetersetting is more than 29.92 in. Hg., the air in this exam-ple has a higher pressure, and is more compressed,indicative of the air found at a lower altitude.Therefore, the pressure altitude is lower than the actualheight above mean sea level.

To calculate pressure altitude without the use of analtimeter, remember that the pressure decreasesapproximately 1 inch of mercury for every 1,000-footincrease in altitude. For example, if the current localaltimeter setting at a 4,000-foot elevation is 30.42, thepressure altitude would be 3,500 feet. (30.42 – 29.92 =.50 in. Hg. 3 1,000 feet = 500 feet. Subtracting 500 feetfrom 4,000 equals 3,500 feet).

The four factors that most affect density altitude are:atmospheric pressure, altitude, temperature, and themoisture content of the air.

ATMOSPHERIC PRESSUREDue to changing weather conditions, atmospheric pres-sure at a given location changes from day to day. If thepressure is lower, the air is less dense. This means ahigher density altitude and less helicopter performance.

Density Altitude—Pressure altitude corrected for nonstandard temper-ature variations. Performance charts for many older aircraft are basedon this value.

Standard Atmosphere—At sea level, the standard atmosphere consistsof a barometric pressure of 29.92 inches of mercury (in. Hg.) or 1013.2millibars, and a temperature of 15°C (59°F). Pressure and temperaturenormally decrease as altitude increases. The standard lapse rate in thelower atmosphere for each 1,000 feet of altitude is approximately 1 in.Hg. and 2°C (3.5°F). For example, the standard pressure and tempera-ture at 3,000 feet mean sea level (MSL) is 26.92 in. Hg. (29.92 – 3) and9°C (15°C – 6°C).

Pressure Altitude—The height above the standard pressure level of29.92 in. Hg. It is obtained by setting 29.92 in the barometric pressurewindow and reading the altimeter.

True Altitude—The actual height of an object above mean sea level.

8-2

ALTITUDEAs altitude increases, the air becomes thinner or lessdense. This is because the atmospheric pressure actingon a given volume of air is less, allowing the air mole-cules to move further apart. Dense air contains more airmolecules spaced closely together, while thin air con-tains less air molecules because they are spaced furtherapart. As altitude increases, density altitude increases.

TEMPERATURETemperature changes have a large affect on density alti-tude. As warm air expands, the air molecules move fur-ther apart, creating less dense air. Since cool aircontracts, the air molecules move closer together, cre-ating denser air. High temperatures cause even low ele-vations to have high density altitudes.

MOISTURE (HUMIDITY)The water content of the air also changes air densitybecause water vapor weighs less than dry air.Therefore, as the water content of the air increases, theair becomes less dense, increasing density altitude anddecreasing performance.

Humidity, also called “relative humidity,” refers to theamount of water vapor contained in the atmosphere,and is expressed as a percentage of the maximumamount of water vapor the air can hold. This amountvaries with temperature; warm air can hold more watervapor, while colder air can hold less. Perfectly dry airthat contains no water vapor has a relative humidity of0 percent, while saturated air that cannot hold any morewater vapor, has a relative humidity of 100 percent.

Humidity alone is usually not considered an importantfactor in calculating density altitude and helicopter per-formance; however, it does contribute. There are norules-of-thumb or charts used to compute the effects ofhumidity on density altitude, so you need to take thisinto consideration by expecting a decrease in hoveringand takeoff performance in high humidity conditions.

HIGH AND LOW DENSITY ALTITUDE CONDITIONSYou need to thoroughly understand the terms “highdensity altitude” and “low density altitude.” In general,high density altitude refers to thin air, while low den-sity altitude refers to dense air. Those conditions thatresult in a high density altitude (thin air) are high ele-vations, low atmospheric pressure, high temperatures,high humidity, or some combination thereof. Lowerelevations, high atmospheric pressure, low tempera-tures, and low humidity are more indicative of lowdensity altitude (dense air). However, high densityaltitudes may be present at lower elevations on hotdays, so it is important to calculate the density altitudeand determine performance before a flight.

One of the ways you can determine density altitude isthrough the use of charts designed for that purpose.[Figure 8-1]. For example, assume you are planning todepart an airport where the field elevation is 1,165 feetMSL, the altimeter setting is 30.10, and the tempera-ture is 70°F. What is the density altitude? First, correctfor nonstandard pressure (30.10) by referring to theright side of the chart, and subtracting 165 feet fromthe field elevation. The result is a pressure altitude of1,000 feet. Then, enter the chart at the bottom, justabove the temperature of 70°F (21°C). Proceed up thechart vertically until you intercept the diagonal 1,000-foot pressure altitude line, then move horizontally tothe left and read the density altitude of approximately2,000 feet. This means your helicopter will perform asif it were at 2,000 feet MSL on a standard day.

Most performance charts do not require you to com-pute density altitude. Instead, the computation is builtinto the performance chart itself. All you have to do isenter the chart with the correct pressure altitude and thetemperature.

WEIGHTLift is the force that opposes weight. As weightincreases, the power required to produce the lift neededto compensate for the added weight must also increase.Most performance charts include weight as one of thevariables. By reducing the weight of the helicopter, youmay find that you are able to safely take off or land at alocation that otherwise would be impossible. However,if you are ever in doubt about whether you can safelyperform a takeoff or landing, you should delay yourtakeoff until more favorable density altitude conditionsexist. If airborne, try to land at a location that has morefavorable conditions, or one where you can make alanding that does not require a hover.

In addition, at higher gross weights, the increasedpower required to hover produces more torque, whichmeans more antitorque thrust is required. In some heli-copters, during high altitude operations, the maximumantitorque produced by the tail rotor during a hovermay not be sufficient to overcome torque even if thegross weight is within limits.

WINDSWind direction and velocity also affect hovering, take-off, and climb performance. Translational lift occursanytime there is relative airflow over the rotor disc.This occurs whether the relative airflow is caused byhelicopter movement or by the wind. As wind speedincreases, translational lift increases, resulting in lesspower required to hover.

The wind direction is also an important consideration.Headwinds are the most desirable as they contribute tothe most increase in performance. Strong crosswinds

8-3

and tailwinds may require the use of more tail rotorthrust to maintain directional control. This increasedtail rotor thrust absorbs power from the engine, whichmeans there is less power available to the main rotorfor the production of lift. Some helicopters even have acritical wind azimuth or maximum safe relative windchart. Operating the helicopter beyond these limitscould cause loss of tail rotor effectiveness.

Takeoff and climb performance is greatly affected bywind. When taking off into a headwind, effective trans-lational lift is achieved earlier, resulting in more lift anda steeper climb angle. When taking off with a tailwind,more distance is required to accelerate through transla-tion lift.

PERFORMANCE CHARTSIn developing performance charts, aircraft manufactur-ers make certain assumptions about the condition of thehelicopter and the ability of the pilot. It is assumed thatthe helicopter is in good operating condition and theengine is developing its rated power. The pilot isassumed to be following normal operating proceduresand to have average flying abilities. Average means apilot capable of doing each of the required tasks cor-rectly and at the appropriate times.

Using these assumptions, the manufacturer devel-ops performance data for the helicopter based on

actual flight tests. However, they do not test the hel-icopter under each and every condition shown on aperformance chart. Instead, they evaluate specificdata and mathematically derive the remaining data.

HOVERING PERFORMANCEHelicopter performance revolves around whether ornot the helicopter can be hovered. More power isrequired during the hover than in any other flightregime. Obstructions aside, if a hover can be maintained,a takeoff can be made, especially with the additionalbenefit of translational lift. Hover charts are provided forin ground effect (IGE) hover and out of ground effect(OGE) hover under various conditions of gross weight,altitude, temperature, and power. The “in ground effect”hover ceiling is usually higher than the “out of groundeffect” hover ceiling because of the added lift benefitproduced by ground effect.

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Altimeter Setting

Pressure Altitude

Conversion Factor

0

-18

°F

°C -12

10

-7

20

-1

30

4

40

10

50

16

60

21

70

27

80

32

90

Outside Air Temperature

App

roxi

mat

eD

ensi

tyA

ltitu

de–

Tho

usan

dsof

Fee

t

13

12

11

10

9

8

7

6

5

4

3

2

1

SL

12,000

11,000

10,000

9,000

8,000

7,000

6,000

5,000

4,000

3,000

2,000

1,000

-1,000

PressureAltitu

de – Feet

Standard

Temperature

Sea Level

Figure 8-1. Density Altitude Chart.

In Ground Effect (IGE) Hover—Hovering close to the surface (usuallyless than one rotor diameter above the surface) under the influence ofground effect.

Out of Ground Effect (OGE) Hover—Hovering greater than one rotordiameter distance above the surface. Because induced drag is greaterwhile hovering out of ground effect, it takes more power to achieve ahover. See Chapter 3—Aerodynamics of Flight for more details on IGEand OGE hover.

8-4

Since the gross weight of your helicopter is less thanthis, you can safely hover with these conditions.

SAMPLE PROBLEM 2Once you reach the remote location in the previousproblem, you will need to hover out of ground effectfor some of the pictures. The pressure altitude at theremote site is 9,000 feet, and you will use 50 poundsof fuel getting there. (The new gross weight is now1,200 pounds.) The temperature will remain at +15°C.Using figure 8-3, can you accomplish the mission?

Enter the chart at 9,000 feet (point A) and proceed topoint B (+15°C). From there determine that the maxi-mum gross weight to hover out of ground effect isapproximately 1,130 pounds (point C). Since yourgross weight is higher than this value, you will not beable to hover with these conditions. To accomplish themission, you will have to remove approximately 70pounds before you begin the flight.

These two sample problems emphasize the importance ofdetermining the gross weight and hover ceiling throughout

DENSITY ALTITUDE 12,600 FT

STANDARD DAY

(Point A)

900 1,000 1,100 1,200 1,300 1,400

GROSS WEIGHT - LBS.

425 450 475 500 525 550 57514

13

12

11

10

9

8

7

6

5

4

3

2

1

0

PR

ES

SU

RE

ALT

ITU

DE

-H

pX

1,00

0F

T.

OAT

°C °F– 20 – 4

+ 14+ 32+ 50+ 68+ 86+ 104

– 10

+ 10+ 20+ 30+ 40

0

OUT OF GROUND EFFECT FULL THROTTLE ( OR LIMIT MANIFOLD

PRESSURE) AND 104% RPMGROSS WEIGHT - KGS.

MAX CONT. OR FULL THROTTLE OGE HOVER CEILING VS. GROSS WEIGHT

600 625

–20

–10

+10+20+30+40

0

OAT°C

(Point B)

(Point C)

Figure 8-3. Out of Ground Effect Hover Ceiling versus GrossWeight Chart.

As density altitude increases, more power is required tohover. At some point, the power required is equal to thepower available. This establishes the hovering ceilingunder the existing conditions. Any adjustment to thegross weight by varying fuel, payload, or both, affectsthe hovering ceiling. The heavier the gross weight, thelower the hovering ceiling. As gross weight isdecreased, the hover ceiling increases.

SAMPLE PROBLEM 1You are to fly a photographer to a remote location totake pictures of the local wildlife. Using figure 8-2, canyou safely hover in ground effect at your departurepoint with the following conditions?

Pressure Altitude..................................8,000 feetTemperature...............................................+15°CTakeoff Gross Weight.....................1,250 poundsR.P.M..........................................................104%

First enter the chart at 8,000 feet pressure altitude(point A), then move right until reaching a point mid-way between the +10°C and +20°C lines (point B).From that point, proceed down to find the maximumgross weight where a 2 foot hover can be achieved. Inthis case, it is approximately 1,280 pounds (point C).

DENSITY ALTITUDE 12,600 FT

STANDARD DAY

1,370

(Point A)

(Point B)

900 1,000 1,100 1,200 1,300 1,400GROSS WEIGHT - LBS.

425 450 475 500 525 550 57514

13

12

11

10

9

8

7

6

5

4

3

2

1

0

OAT°C

PR

ES

SU

RE

ALT

ITU

DE

-H

pX

1,00

0F

T.

OAT

°C °F– 20 – 4

+ 14+ 32+ 50+ 68+ 86+ 104

– 10

+ 10+ 20+ 30+ 40

0

IN GROUND EFFECT AT 2 FOOT SKID CLEARANCE FULL THROTTLE AND 104% RPM

GROSS WEIGHT - KGS.

–20–10

+10+20+30+40

0

IGE HOVER CEILING VS. GROSS WEIGHT

(Point C)

Figure 8-2. In Ground Effect Hover Ceiling versus GrossWeight Chart.

8-5

the entire flight operation. Being able to hover at the take-off location with a certain gross weight does not ensure thesame performance at the landing point. If the destinationpoint is at a higher density altitude because of higher ele-vation, temperature, and/or relative humidity, more poweris required to hover. You should be able to predict whetherhovering power will be available at the destination byknowing the temperature and wind conditions, using theperformance charts in the helicopter flight manual, andmaking certain power checks during hover and in flightprior to commencing the approach and landing.

TAKEOFF PERFORMANCEIf takeoff charts are included in the rotorcraft flight man-ual, they usually indicate the distance it takes to clear a 50-foot obstacle based on various conditions of weight,pressure altitude, and temperature. In addition, the valuescomputed in the takeoff charts usually assume that theflight profile is per the applicable height-velocity diagram.

SAMPLE PROBLEM 3In this example, determine the distance to clear a 50-foot obstacle with the following conditions:

Pressure Altitude..................................5,000 feetTakeoff Gross Weight.....................2,850 poundsTemperature .................................................95°F

Using figure 8-4, locate 2,850 pounds in the first col-umn. Since the pressure altitude of 5,000 feet is not oneof the choices in column two, you have to interpolatebetween the values from the 4,000- and 6,000-footlines. Follow each of these rows out to the column

headed by 95°F. The values are 1,102 feet and 1,538feet. Since 5,000 is halfway between 4,000 and 6,000,the interpolated value should be halfway between thesetwo values or 1,320 feet ([1,102 + 1,538] 4 2 = 1,320).

CLIMB PERFORMANCEMost of the factors affecting hover and takeoff per-formance also affect climb performance. In addition,turbulent air, pilot techniques, and overall condition ofthe helicopter can cause climb performance to vary.

A helicopter flown at the “best rate-of-climb” speedwill obtain the greatest gain in altitude over a givenperiod of time. This speed is normally used during theclimb after all obstacles have been cleared and is usu-ally maintained until reaching cruise altitude. Rate ofclimb must not be confused with angle of climb.Angle of climb is a function of altitude gained over agiven distance. The best rate-of-climb speed results inthe highest climb rate, but not the steepest climb angleand may not be sufficient to clear obstructions. The“best angle-of-climb” speed depends upon the poweravailable. If there is a surplus of power available, thehelicopter can climb vertically, so the best angle-of-climb speed is zero.

Wind direction and speed have an effect on climb per-formance, but it is often misunderstood. Airspeed isthe speed at which the helicopter is moving throughthe atmosphere and is unaffected by wind.Atmospheric wind affects only the groundspeed, orspeed at which the helicopter is moving over theearth’s surface. Thus, the only climb performance

Gross Weight Pounds

Pressure Altitude

Feet

At –13°F–25°C

At 23°F–5°C

At 59°F15°C

At 95°F35°C

TAKE-OFF DISTANCE (FEET TO CLEAR 50 FOOT OBSTACLE)

373 400 428 461 567

531 568 611 654 811

743 770 861 939

1,201

401 434 462 510 674

569 614 660 727 975

806 876 940

1,064 1,527

430 461 494 585 779

613 660 709 848

1,144

864 929

1,017 1,255

– –

2,150

2,500

2,850

458 491 527 677 896

652 701 759 986

1,355

929 1,011 1,102 1,538

1,320

SL 2,000 4,000 6,000 8,000 SL 2,000 4,000 6,000 8,000 SL 2,000 4,000 6,000 8,000

Figure 8-4. Takeoff Distance Chart.

8-6

affected by atmospheric wind is the angle of climb andnot the rate of climb.

SAMPLE PROBLEM 4Determine the best rate of climb using figure 8-5. Usethe following conditions:

Pressure Altitude................................12,000 feetOutside Air Temperature ...........................+10°CGross Weight ..................................3,000 poundsPower ...........................................Takeoff PowerAnti-ice ..........................................................ONIndicated Airspeed .................................52 knots

With this chart, first locate the temperature of +10°C(point A). Then proceed up the chart to the 12,000-footpressure altitude line (point B). From there, move hori-zontally to the right until you intersect the 3,000-footline (point C). With this performance chart, you mustnow determine the rate of climb with anti-ice off andthen subtract the rate of climb change with it on. Frompoint C, go to the bottom of the chart and find that themaximum rate of climb with anti-ice off is approxi-mately 890 feet per minute. Then, go back to point Cand up to the anti-ice-on line (point D). Proceed hori-zontally to the right and read approximately 240 feetper minute change (point E). Now subtract 240 from890 to get a maximum rate of climb, with anti-ice on,of 650 feet per minute.

Other rate-of-climb charts use density altitude as astarting point. [Figure 8-6] While it cleans up the chartsomewhat, you must first determine density altitude.Notice also that this chart requires a change in the indi-cated airspeed with a change in altitude.

RATE OF CLIMB — MAXIMUM TAKEOFF POWER

–40 –20 0 20 40 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32OAT — ° C ANTI-ICE OFF RATE OF CLIMB — FT./MIN. (X 100)

0100200300400500

R/C

orre

ctio

n—

FT.

/MIN

.

This Chart is Based on: Indicated Airspeed 60 MPH 52 KNOTS N2 ENGINE RPM 100%

PR

ES

SU

RE

ALT

ITU

DE

—FT

.

20,0

0018

,000

16,0

0014

,000

12,0

0010

,000

6,00

0

4,0002,000S.L.

GRO

SSW

EIGHT

POUNDS

2,0002,2002,4002,6002,8003,0003,200

8,00

0

(Point A)

(Point B) (Point C)

(Point D)

(Point E)

890 ft/min. – 240 ft/min.

650 ft/min.

HOT DAY

ANTI-ICE ON

Figure 8-5. Maximum Rate-of-Climb Chart.

400 600 800 1,000 1,200 1,400

12,000

10,000

8,000

6,000

4,000

2,000

0

Rate of Climb, Feet Per Minute

Den

sity

Alt

itu

de

—F

eet

RATE OF CLIMB/DENSITY ALTITUDE 2,350 LBS. GROSS WEIGHT

BEST RATE OF CLIMB SPEED VARIES WITH ALTITUDE; 57 MPH AT S.L. DECREASING TO 49

MPH, IAS AT 12,000 FT.

Figure 8-6. This chart uses density altitude in determiningmaximum rate of climb.

9-1

From the previous chapters, it should be apparent thatno two helicopters perform the same way. Even whenflying the same model of helicopter, wind, temperature,humidity, weight, and equipment make it difficult topredict just how the helicopter will perform. Therefore,this chapter presents the basic flight maneuvers in away that would apply to a majority of the helicopters.In most cases, the techniques described apply to smalltraining helicopters with:

• A single, main rotor rotating in a counterclock-wise direction (looking downward on the rotor).

• An antitorque system.

Where a technique differs, it will be noted. For example,a power increase on a helicopter with a clockwise rotorsystem requires right antitorque pedal pressure insteadof left pedal pressure. In many cases, the terminology“apply proper pedal pressure” is used to indicate bothtypes of rotor systems. However, when discussing throt-tle coordination to maintain proper r.p.m., there will beno differentiation between those helicopters with a gov-ernor and those without. In a sense, the governor is doingthe work for you. In addition, instead of using the termscollective pitch control and the cyclic pitch controlthroughout the chapter, these controls are referred to asjust collective and cyclic.

Because helicopter performance varies with differentweather conditions and aircraft loading, specific noseattitudes and power settings will not be discussed. Inaddition, this chapter does not detail each and everyattitude of a helicopter in the various flight maneuvers,nor each and every move you must make in order toperform a given maneuver.

When a maneuver is presented, there will be a briefdescription, followed by the technique to accomplishthe maneuver. In most cases, there is a list of commonerrors at the end of the discussion.

PREFLIGHTBefore any flight, you must ensure the helicopter isairworthy by inspecting it according to the rotorcraftflight manual, pilot’s operating handbook, or otherinformation supplied either by the operator or the man-ufacturer. Remember that as pilot in command, it is

your responsibility to ensure the aircraft is in an air-worthy condition.

In preparation for flight, the use of a checklist is importantso that no item is overlooked. Follow the manufacturer’ssuggested outline for both the inside and outside inspec-tion. This ensures that all the items the manufacturerfeels are important are checked. Obviously, if there areother items you feel might need attention, inspectthem as well.

MINIMUM EQUIPMENT LISTS (MELS) ANDOPERATIONS WITH INOPERATIVEEQUIPMENTThe Code of Federal Regulations (CFRs) requires thatall aircraft instruments and installed equipment beoperative prior to each departure. However, when theFAA adopted the minimum equipment list (MEL)concept for 14 CFR part 91 operations, flights wereallowed with inoperative items, as long as the inopera-tive items were determined to be nonessential for safeflight. At the same time, it allowed part 91 operators,without an MEL, to defer repairs on nonessentialequipment within the guidelines of part 91.

There are two primary methods of deferring maintenanceon rotorcraft operating under part 91. They are the defer-ral provision of 14 CFR part 91, section 91.213(d) and anFAA-approved MEL.

The deferral provision of section 91.213(d) is widelyused by most pilot/operators. Its popularity is due tosimplicity and minimal paperwork. When inoperativeequipment is found during preflight or prior to depar-ture, the decision should be to cancel the flight, obtainmaintenance prior to flight, or to defer the item or equipment.

Maintenance deferrals are not used for in-flight discrep-ancies. The manufacturer's RFM/POH procedures areto be used in those situations. The discussion that

Minimum Equipment List (MEL)—An inventory of instruments andequipment that may legally be inoperative, with the specific conditionsunder which an aircraft may be flown with such items inoperative.

9-2

follows assumes that the pilot wishes to defer mainte-nance that would ordinarily be required prior to flight.

Using the deferral provision of section 91.213(d), thepilot determines whether the inoperative equipment isrequired by type design, the CFRs, or ADs. If the inop-erative item is not required, and the helicopter can besafely operated without it, the deferral may be made.The inoperative item shall be deactivated or removed andan INOPERATIVE placard placed near the appropriateswitch, control, or indicator. If deactivation or removalinvolves maintenance (removal always will), it must beaccomplished by certificated maintenance personnel.

For example, if the position lights (installed equipment)were discovered to be inoperative prior to a daytimeflight, the pilot would follow the requirements of sec-tion 91.213(d).

The deactivation may be a process as simple as the pilotpositioning a circuit breaker to the OFF position, or ascomplex as rendering instruments or equipment totallyinoperable. Complex maintenance tasks require a cer-tificated and appropriately rated maintenance person toperform the deactivation. In all cases, the item or equip-ment must be placarded INOPERATIVE.

All rotorcraft operated under part 91 are eligible to usethe maintenance deferral provisions of section 91.213(d).However, once an operator requests an MEL, and a Letterof Authorization (LOA) is issued by the FAA, then theuse of the MEL becomes mandatory for that helicopter.All maintenance deferrals must be accomplished inaccordance with the terms and conditions of the MEL andthe operator-generated procedures document.

The use of an MEL for rotorcraft operated under part 91also allows for the deferral of inoperative items orequipment. The primary guidance becomes the FAA-approved MEL issued to that specific operator and N-numbered helicopter.

The FAA has developed master minimum equipmentlists (MMELs) for rotorcraft in current use. Upon writ-ten request by a rotorcraft operator, the local FAA FlightStandards District Office (FSDO) may issue the appro-priate make and model MMEL, along with an LOA, andthe preamble. The operator then develops operationsand maintenance (O&M) procedures from the MMEL.This MMEL with O&M procedures now becomes theoperator's MEL. The MEL, LOA, preamble, and proce-dures document developed by the operator must be onboard the helicopter when it is operated.

The FAA considers an approved MEL to be a supple-mental type certificate (STC) issued to an aircraft byserial number and registration number. It thereforebecomes the authority to operate that aircraft in a condi-tion other than originally type certificated.

With an approved MEL, if the position lights were dis-covered inoperative prior to a daytime flight, the pilotwould make an entry in the maintenance record or dis-crepancy record provided for that purpose. The item isthen either repaired or deferred in accordance with theMEL. Upon confirming that daytime flight with inopera-tive position lights is acceptable in accordance with theprovisions of the MEL, the pilot would leave the positionlights switch OFF, open the circuit breaker (or whateveraction is called for in the procedures document), and plac-ard the position light switch as INOPERATIVE.

There are exceptions to the use of the MEL for deferral.For example, should a component fail that is not listedin the MEL as deferrable (the rotor tachometer, enginetachometer, or cyclic trim, for example), then repairsare required to be performed prior to departure. If main-tenance or parts are not readily available at that location, a special flight permit can be obtained fromthe nearest FSDO. This permit allows the helicopter tobe flown to another location for maintenance. Thisallows an aircraft that may not currently meet applica-ble airworthiness requirements, but is capable of safeflight, to be operated under the restrictive special termsand conditions attached to the special flight permit.

Deferral of maintenance is not to be taken lightly, anddue consideration should be given to the effect an inop-erative component may have on the operation of a helicopter, particularly if other items are inoperative.Further information regarding MELs and operationswith inoperative equipment can be found in AC 91-67,Minimum Equipment Requirements for GeneralAviation Operations Under FAR Part 91.

ENGINE START AND ROTOR ENGAGEMENTDuring the engine start, rotor engagement, and systemsground check, use the manufacturer’s checklists. If aproblem arises, have it checked before continuing.Prior to performing these tasks, however, make surethe area near the helicopter is clear of personnel andequipment. Helicopters are safe and efficient flyingmachines as long as they are operated within theparameters established by the manufacturer.

ROTOR SAFETY CONSIDERATIONSThe exposed nature of the main and tail rotors deservespecial caution. You must exercise extreme care whentaxiing near hangars or obstructions since the distancebetween the rotor blade tips and obstructions is verydifficult to judge. [Figure 9-1] In addition, you cannotsee the tail rotor of some helicopters from the cabin.Therefore, when hovering backwards or turning inthose helicopters, allow plenty of room for tail rotorclearance. It is a good practice to glance over yourshoulder to maintain this clearance.

9-3

Another rotor safety consideration is the thrust a heli-copter generates. The main rotor system is capable ofblowing sand, dust, snow, ice, and water at high veloci-ties for a significant distance causing injury to nearbypeople and damage to buildings, automobiles, and otheraircraft. Loose snow, can severely reduce visibility andobscure outside visual references. Any airborne debrisnear the helicopter can be ingested into the engine airintake or struck by the main and tail rotor blades.

SAFETY IN AND AROUND HELICOPTERSPeople have been injured, some fatally, in helicopteraccidents that would not have occurred had they beeninformed of the proper method of boarding or deplan-ing. A properly briefed passenger should never beendangered by a spinning rotor. The simplest methodof avoiding accidents of this sort is to stop the rotorsbefore passengers are boarded or allowed to depart.Because this action is not always practicable, and torealize the vast and unique capabilities of the helicop-ter, it is often necessary to take on passengers or todeplane them while the engine and rotors are turning.To avoid accidents, it is essential that all persons asso-ciated with helicopter operations, including passengers,be made aware of all possible hazards and instructed asto how they can be avoided.

Persons directly involved with boarding or deplaningpassengers, aircraft servicing, rigging, or hooking upexternal loads, etc., should be instructed as to theirduties. It would be difficult, if not impossible, to covereach and every type of operation related to helicopters.A few of the more obvious and common ones are cov-ered below.

RAMP ATTENDANTS AND AIRCRAFT SERVIC-ING PERSONNEL—These personnel should beinstructed as to their specific duties, and the propermethod of fulfilling them. In addition, the ramp atten-dant should be taught to:

1. keep passengers and unauthorized persons out ofthe helicopter landing and takeoff area.

2. brief passengers on the best way to approach andboard a helicopter with its rotors turning.

AIRCRAFT SERVICING—The helicopter rotor bladesshould be stopped, and both the aircraft and the refuel-ing unit properly grounded prior to any refueling oper-ation. You, as the pilot, should ensure that the propergrade of fuel and the proper additives, when required,are being dispensed.

Refueling the aircraft, while the blades are turning,known as "hot refueling," may be practical for certaintypes of operation. However, this can be hazardous ifnot properly conducted. Pilots should remain at theflight controls; and refueling personnel should beknowledgeable about the proper refueling proceduresand properly briefed for specific helicopter makes andmodels.

Refueling units should be positioned to ensure ade-quate rotor blade clearance. Persons not involved withthe refueling operation should keep clear of the area.

Smoking must be prohibited in and around the aircraftduring all refueling operations.

EXTERNAL-LOAD RIGGERS—Rigger training ispossibly one of the most difficult and continuallychanging problems of the helicopter external-loadoperator. A poorly rigged cargo net, light standard, orload pallet could result in a serious and costly accident.It is imperative that all riggers be thoroughly trained tomeet the needs of each individual external-load opera-tion. Since rigging requirements may vary severaltimes in a single day, proper training is of the utmostimportance to safe operations.

PILOT AT THE FLIGHT CONTROLS—Many heli-copter operators have been lured into a "quick turn-around" ground operation to avoid delays at airportterminals and to minimize stop/start cycles of theengine. As part of this quick turnaround, the pilot mightleave the cockpit with the engine and rotors turning.Such an operation can be extremely hazardous if a gustof wind disturbs the rotor disc, or the collective flightcontrol moves causing lift to be generated by the rotorsystem. Either occurrence may cause the helicopter toroll or pitch, resulting in a rotor blade striking the tail-boom or the ground. Good operating procedures dictatethat pilots remain at the flight controls whenever theengine is running and the rotors are turning.

EXTERNAL-LOAD HOOKUP PERSONNEL—There are several areas in which these personnelshould be knowledgeable. First, they should know thelifting capability of the helicopters involved. Sincesome operators have helicopter models with almost

Figure 9-1. Exercise extreme caution when hovering nearbuildings or other aircraft.

9-4

identical physical characteristics but different liftingcapabilities, this knowledge is essential. For example,a hookup person may be working with a turbochargedhelicopter on a high altitude project when a non-tur-bocharged helicopter, which looks exactly the same tothe ground crew, comes to pick up a load. If thehookup person attaches a load greater than the non-turbocharged helicopter can handle, a potentiallydangerous situation could exist.

Second, know the pilots. The safest plan is to stan-dardize all pilots in the manner in which sling loadsare picked up and released. Without pilot standardiza-tion, the operation could be hazardous. The operatorshould standardize the pilots on operations while personnel are beneath the helicopter.

Third, know the cargo. Many items carried via sling arevery fragile, others can take a beating. The hookup per-son should always know when a hazardous article isinvolved and the nature of the hazard, such as explo-sives, radioactive materials, and toxic chemicals. Inaddition to knowing this, the hookup person should befamiliar with the types of protective gear or clothingand the actions necessary to protect their own safetyand that of the operation.

Fourth, know appropriate hand signals. When directradio communications between ground and flight per-sonnel are not used, the specific meaning of hand signals should be coordinated prior to operations.

Fifth, know emergency procedures. Ground and flightpersonnel should fully agree to and understand theactions to be taken by all participants in the event ofemergencies. This prior planning is essential to avoidinjuries to all concerned.

PASSENGERS—All persons who board a helicopterwhile its rotors are turning should be instructed in thesafest means of doing so. Naturally, if you are at thecontrols, you may not be able to conduct a boardingbriefing. Therefore, the individual who arranged for thepassengers' flight or is assigned as the ramp attendantshould accomplish this task. The exact procedures mayvary slightly from one helicopter model to another, butin general the following should suffice.

When boarding—

1. stay away from the rear of the helicopter.

2. approach or leave the helicopter in a crouchingmanner.

3. approach from the side or front, but never out ofthe pilot's line of vision.

4. carry tools horizontally, below waist level, neverupright or over the shoulder.

5. hold firmly to hats and loose articles.

6. never reach up or dart after a hat or other objectthat might be blown off or away.

7. protect eyes by shielding them with a hand or bysquinting.

8. if suddenly blinded by dust or a blowing object,stop and crouch lower; or better yet, sit down andwait for help.

9. never grope or feel your way toward or awayfrom the helicopter.

Since few helicopters carry cabin attendants, you, asthe pilot, will have to conduct the pre-takeoff and pre-landing briefings. The type of operation dictates whatsort of briefing is necessary. All briefings shouldinclude the following:

1. The use and operation of seatbelts for takeoff, enroute, and landing.

2. For overwater flights, the location and use offlotation gear and other survival equipment thatmight be on board. You should also include howand when to abandon the helicopter should aditching be necessary.

3. For flights over rough or isolated terrain, alloccupants should be told where maps and sur-vival gear are located.

4. Passengers should be instructed as to whatactions and precautions to take in the event of anemergency, such as the body position for bestspinal protection against a high vertical impactlanding (erect with back firmly against the seatback); and when and how to exit after landing.Ensure that passengers are aware of the locationof the fire extinguisher and survival equipment.

5. Smoking should not be permitted within 50 feetof an aircraft on the ground. Smoking could bepermitted, at the discretion of the pilot, exceptunder the following conditions:

• during all ground operations.

• during, takeoff or landing.

• when carrying flammable or hazardous materials.

When passengers are approaching or leaving a helicop-ter that is sitting on a slope with the rotors turning, theyshould approach and depart downhill. This affords thegreatest distance between the rotor blades and theground. If this involves walking around the helicopter,they should always go around the front, never the rear.

9-5

VERTICAL TAKEOFF TO A HOVERA vertical takeoff, or takeoff to a hover, is a maneuverin which the helicopter is raised vertically from the sur-face to the normal hovering altitude (2 to 5 feet) with aminimum of lateral or longitudinal movement.

TECHNIQUEPrior to any takeoff or maneuver, you should ensurethat the area is clear of other traffic. Then, head the hel-icopter into the wind, if possible. Place the cyclic in theneutral position, with the collective in the full downposition. Increase the throttle smoothly to obtain andmaintain proper r.p.m., then raise the collective. Usesmooth, continuous movement, coordinating the throt-tle to maintain proper r.p.m. As you increase the collec-tive, the helicopter becomes light on the skids, andtorque tends to cause the nose to swing or yaw to theright unless sufficient left antitorque pedal is used tomaintain the heading. (On helicopters with a clockwisemain rotor system, the yaw is to the left and right pedalmust be applied.)

As the helicopter becomes light on the skids, make nec-essary cyclic pitch control adjustments to maintain alevel attitude. When airborne, use the antitorque pedalsto maintain heading and the collective to ensure contin-uous vertical assent to the normal hovering altitude.When hovering altitude is reached, use the throttle andcollective to control altitude, and the cyclic to maintaina stationary hover. Use the antitorque pedals to main-tain heading. When a stabilized hover is achieved,check the engine instruments and note the powerrequired to hover. You should also note the position ofthe cyclic. Cyclic position varies with wind and theamount and distribution of the load.

Excessive movement of any flight control requires achange in the other flight controls. For example, ifwhile hovering, you drift to one side, you naturallymove the cyclic in the opposite direction. When you dothis, part of the vertical thrust is diverted, resulting in aloss of altitude. To maintain altitude, you must increasethe collective. This increases drag on the blades andtends to slow them down. To counteract the drag andmaintain r.p.m., you need to increase the throttle.Increased throttle means increased torque, so you mustadd more pedal pressure to maintain the heading. Thiscan easily lead to overcontrolling the helicopter.However, as your level of proficiency increases, prob-lems associated with overcontrolling decrease.

COMMON ERRORS1. Failing to ascend vertically as the helicopter

becomes airborne.

2. Pulling through on the collective after becomingairborne, causing the helicopter to gain too muchaltitude.

3. Overcontrolling the antitorque pedals, which notonly changes the handling of the helicopter, butalso changes the r.p.m.

4. Reducing throttle rapidly in situations whereproper r.p.m. has been exceeded. This usuallyresults in exaggerated heading changes and lossof lift, resulting in loss of altitude.

HOVERINGHovering is a maneuver in which the helicopter is main-tained in a nearly motionless flight over a referencepoint at a constant altitude and on a constant heading.The maneuver requires a high degree of concentrationand coordination.

TECHNIQUETo maintain a hover over a point, you should look forsmall changes in the helicopter’s attitude and altitude.When you note these changes, make the necessary con-trol inputs before the helicopter starts to move from thepoint. To detect small variations in altitude or position,your main area of visual attention needs to be somedistance from the aircraft, using various points on thehelicopter or the tip-path plane as a reference. Lookingtoo close or looking down leads to overcontrolling.Obviously, in order to remain over a certain point, youshould know where the point is, but your attentionshould not be focused there.

As with a takeoff, you control altitude with the collec-tive and maintain a constant r.p.m. with the throttle.Use the cyclic to maintain the helicopter’s position andthe pedals to control heading. To maintain the helicopter in a stabilized hover, make small, smooth,coordinated corrections. As the desired effect occurs,remove the correction in order to stop the helicopter’smovement. For example, if the helicopter begins tomove rearward, you need to apply a small amount offorward cyclic pressure. However, neutralize this pres-sure just before the helicopter comes to a stop, or it willbegin to move forward.

After you gain experience, you will develop a certain“feel” for the helicopter. You will feel and see smalldeviations, so you can make the corrections before thehelicopter actually moves. A certain relaxed loosenessdevelops, and controlling the helicopter becomes sec-ond nature, rather than a mechanical response.

COMMON ERRORS1. Tenseness and slow reactions to movements of

the helicopter.

2. Failure to allow for lag in cyclic and collectivepitch, which leads to overcontrolling.

9-6

3. Confusing attitude changes for altitude changes,which result in improper use of the controls.

4. Hovering too high, creating a hazardous flightcondition.

5. Hovering too low, resulting in occasional touch-down.

HOVERING TURNA hovering turn is a maneuver performed at hoveringaltitude in which the nose of the helicopter is rotatedeither left or right while maintaining position over areference point on the surface. The maneuver requiresthe coordination of all flight controls and demands pre-cise control near the surface. You should maintain aconstant altitude, rate of turn, and r.p.m.

TECHNIQUEInitiate the turn in either direction by applying anti-torque pedal pressure toward the desired direction. Itshould be noted that during a turn to the left, you needto add more power because left pedal pressureincreases the pitch angle of the tail rotor, which, in turn,requires additional power from the engine. A turn to theright requires less power. (On helicopters with a clock-wise rotating main rotor, right pedal increases the pitchangle and, therefore, requires more power.)

As the turn begins, use the cyclic as necessary (usuallyinto the wind) to keep the helicopter over the desiredspot. To continue the turn, you need to add more and

more pedal pressure as the helicopter turns to the cross-wind position. This is because the wind is striking thetail surface and tail rotor area, making it more difficultfor the tail to turn into the wind. As pedal pressuresincrease due to crosswind forces, you must increase thecyclic pressure into the wind to maintain position. Usethe collective with the throttle to maintain a constantaltitude and r.p.m. [Figure 9-2]

After the 90° portion of the turn, you need to decreasepedal pressure slightly to maintain the same rate ofturn. Approaching the 180°, or downwind, portion,you need to anticipate opposite pedal pressure due tothe tail moving from an upwind position to a down-wind position. At this point, the rate of turn has a ten-dency to increase at a rapid rate due to theweathervaning tendency of the tail surfaces. Becauseof the tailwind condition, you need to hold rearwardcyclic pressure to keep the helicopter over the samespot.

Because of the helicopter’s tendency to weathervane,maintaining the same rate of turn from the 180° posi-tion actually requires some pedal pressure opposite thedirection of turn. If you do not apply opposite pedalpressure, the helicopter tends to turn at a faster rate.The amount of pedal pressure and cyclic deflectionthroughout the turn depends on the wind velocity. Asyou finish the turn on the upwind heading, applyopposite pedal pressure to stop the turn. Graduallyapply forward cyclic pressure to keep the helicopterfrom drifting.

Cyclic - Forward

Pedal - Some left in hover, more left to start turn to left.

Cyclic - Right

Pedal - Most left pressure in turn.

Cyclic - Rearward

Pedal - Changing from left to right pressure.

Cyclic - Left

Pedal - Most right pedal pressure in turn.

Cyclic - Forward

Pedal - Some right to stop turn, then left to maintain heading.

Collective - Power required to hover at desired height.

Throttle – As necessary to maintain r.p.m.

Collective -Most power in turn.

Throttle – As necessary to maintain r.p.m.

Collective - Power reducing.

Throttle – As necessary to maintain r.p.m.

Collective - Least power in turn.

Throttle – As necessary to maintain r.p.m.

Collective - Increasing as left pedal applied.

Throttle – As necessary to maintain r.p.m.

WIND

Figure 9-2. Left turns in helicopters with a counterclockwise rotating main rotor are more difficult to execute because the tailrotor demands more power. This requires that you compensate with additional collective pitch and increased throttle. Youmight want to refer to this graphic throughout the remainder of the discussion on a hovering turn to the left.

9-7

Control pressures and direction of application changecontinuously throughout the turn. The most dramaticchange is the pedal pressure (and corresponding powerrequirement) necessary to control the rate of turn as thehelicopter moves through the downwind portion of themaneuver.

Turns can be made in either direction; however, in ahigh wind condition, the tail rotor may not be able toproduce enough thrust, which means you will not beable to control a turn to the right in a counterclockwiserotor system. Therefore, if control is ever question-able, you should first attempt to make a 90° turn to theleft. If sufficient tail rotor thrust exists to turn thehelicopter crosswind in a left turn, a right turn canbe successfully controlled. The opposite applies tohelicopters with clockwise rotor systems. In thiscase, you should start your turn to the right.Hovering turns should be avoided in winds strongenough to preclude sufficient aft cyclic control tomaintain the helicopter on the selected surfacereference point when headed downwind. Checkthe flight manual for the manufacturer’s recom-mendations for this limitation.

COMMON ERRORS1. Failing to maintain a slow, constant rate of turn.

2. Failing to maintain position over the referencepoint.

3. Failing to maintain r.p.m. within normal range.

4. Failing to maintain constant altitude.

5. Failing to use the antitorque pedals properly.

HOVERING—FORWARD FLIGHTYou normally use forward hovering flight to move a helicopter to a specific location, and it is usually begunfrom a stationary hover. During the maneuver, constantgroundspeed, altitude, and heading should be maintained.

TECHNIQUEBefore starting, pick out two references directly infront and in line with the helicopter. These referencepoints should be kept in line throughout the maneuver.[Figure 9-3]

Begin the maneuver from a normal hovering altitude byapplying forward pressure on the cyclic. As movementbegins, return the cyclic toward the neutral position tokeep the groundspeed at a slow rate—no faster than abrisk walk. Throughout the maneuver, maintain aconstant groundspeed and path over the ground withthe cyclic, a constant heading with the antitorque

pedals, altitude with the collective, and the properr.p.m. with the throttle.

To stop the forward movement, apply reward cyclicpressure until the helicopter stops. As forward motionstops, return the cyclic to the neutral position to pre-vent rearward movement. Forward movement can alsobe stopped by simply applying rearward pressure tolevel the helicopter and let it drift to a stop.

COMMON ERRORS1. Exaggerated movement of the cyclic, resulting in

erratic movement over the surface.

2. Failure to use the antitorque pedals properly,resulting is excessive heading changes.

3. Failure to maintain desired hovering altitude.

4. Failure to maintain proper r.p.m.

HOVERING—SIDEWARD FLIGHTSideward hovering flight may be necessary to movethe helicopter to a specific area when conditions makeit impossible to use forward flight. During the maneu-ver, a constant groundspeed, altitude, and headingshould be maintained.

TECHNIQUEBefore starting sideward hovering flight, make sure thearea you are going to hover into is clear. Then pick twopoints of reference in a line in the direction of sidewardhovering flight to help you maintain the proper ground

Reference Points

Figure 9-3. To maintain a straight ground track, use two refer-ence points in line and at some distance in front of the helicopter.

9-8

track. These reference points should be kept in linethroughout the maneuver. [Figure 9-4]

Begin the maneuver from a normal hovering altitudeby applying cyclic toward the side in which themovement is desired. As the movement begins, returnthe cyclic toward the neutral position to keep thegroundspeed at a slow rate—no faster than a briskwalk. Throughout the maneuver, maintain a constantgroundspeed and ground track with cyclic. Maintainheading, which in this maneuver is perpendicular tothe ground track, with the antitorque pedals, and aconstant altitude with the collective. Use the throttleto maintain the proper operating r.p.m.

To stop the sideward movement, apply cyclic pres-sure in the direction opposite to that of movementand hold it until the helicopter stops. As motionstops, return the cyclic to the neutral position toprevent movement in the opposite direction.Applying sufficient opposite cyclic pressure tolevel the helicopter may also stop sideward move-ment. The helicopter then drifts to a stop.

COMMON ERRORS1. Exaggerated movement of the cyclic, resulting in

overcontrolling and erratic movement over thesurface.

2. Failure to use proper antitorque pedal control,resulting in excessive heading change.

3. Failure to maintain desired hovering altitude.

4. Failure to maintain proper r.p.m.

5. Failure to make sure the area is clear prior tostarting the maneuver.

HOVERING—REARWARD FLIGHTRearward hovering flight may be necessary to move thehelicopter to a specific area when the situation is suchthat forward or sideward hovering flight cannot be used.During the maneuver, maintain a constant groundspeed,altitude, and heading. Due to the limited visibilitybehind a helicopter, it is important that you make surethat the area behind the helicopter is cleared beforebeginning the maneuver. Use of ground personnel is rec-ommended.

TECHNIQUEBefore starting rearward hovering flight, pick out tworeference points in front of, and in line with the heli-copter just like you would if you were hovering for-ward. [Figure 9-3] The movement of the helicoptershould be such that these points remain in line.

Begin the maneuver from a normal hovering altitude byapplying rearward pressure on the cyclic. After themovement has begun, position the cyclic to maintain aslow groundspeed (no faster than a brisk walk).Throughout the maneuver, maintain constant ground-speed and ground track with the cyclic, a constantheading with the antitorque pedals, constant altitudewith the collective, and the proper r.p.m. with the throttle.

To stop the rearward movement, apply forward cyclicand hold it until the helicopter stops. As the motionstops, return the cyclic to the neutral position. Also, asin the case of forward and sideward hovering flight,opposite cyclic can be used to level the helicopter andlet it drift to a stop.

COMMON ERRORS1. Exaggerated movement of the cyclic resulting in

overcontrolling and an uneven movement overthe surface.

2. Failure to use the antitorque pedals properly,resulting in excessive heading change.

3. Failure to maintain desired hovering altitude.

4. Failure to maintain proper r.p.m.

5. Failure to make sure the area is clear prior tostarting the maneuver.

TAXIINGTaxiing refers to operations on, or near the surface oftaxiways or other prescribed routes. In helicopters,there are three different types of taxiing.

Reference Points

Figure 9-4. The key to hovering sideward is establishing atleast two reference points that help you maintain a straighttrack over the ground while keeping a constant heading.

9-9

HOVER TAXIA "hover taxi" is used when operating below 25 feetAGL. [Figure 9-5] Since hover taxi is just like forward,sideward, or rearward hovering flight, the technique toperform it will not be presented here.

AIR TAXIAn "air taxi" is preferred when movements requiregreater distances within an airport or heliport bound-ary. [Figure 9-6] In this case, you basically fly to yournew location; however, you are expected to remainbelow 100 feet AGL, and to avoid overflight of otheraircraft, vehicles, and personnel.

TECHNIQUEBefore starting, determine the appropriate airspeed andaltitude combination to remain out of the cross-hatchedor shaded areas of the height-velocity diagram.Additionally, be aware of crosswind conditions thatcould lead to loss of tail rotor effectiveness. Pick outtwo references directly in front of the helicopter for theground path desired. These reference points should bekept in line throughout the maneuver.

Begin the maneuver from a normal hovering altitudeby applying forward pressure on the cyclic. As move-ment begins, attain the desired airspeed with the cyclic.Control the desired altitude with the collective, and

r.p.m. with the throttle. Throughout the maneuver,maintain a desired groundspeed and ground track withthe cyclic, a constant heading with antitorque pedals,the desired altitude with the collective, and properoperating r.p.m. with the throttle.

To stop the forward movement, apply aft cyclic pressureto reduce forward speed. Simultaneously lower the col-lective to initiate a descent to hover altitude. As forward motion stops, return the cyclic to the neutral posi-tion to prevent rearward movement. When at the properhover altitude, increase the collective as necessary.

COMMON ERRORS1. Erratic movement of the cyclic, resulting in

improper airspeed control and erratic movementover the surface.

2. Failure to use antitorque pedals properly, result-ing in excessive heading changes.

3. Failure to maintain desired altitude.

4. Failure to maintain proper r.p.m.

5. Overflying parked aircraft causing possible dam-age from rotor downwash.

6. Flying in the cross-hatched or shaded area of theheight-velocity diagram.

7. Flying in a crosswind that could lead to loss oftail rotor effectiveness.

SURFACE TAXIA "surface taxi," for those helicopters with wheels, isused whenever you wish to minimize the effects ofrotor downwash. [Figure 9-7]

TECHNIQUEThe helicopter should be in a stationary position on thesurface with the collective full down and the r.p.m. thesame as that used for a hover. This r.p.m. should bemaintained throughout the maneuver. Then, move thecyclic slightly forward and apply gradual upward pres-sure on the collective to move the helicopter forward

Hover Taxi (25 Feet or Less)

Poor Surface Conditions or Skid Type Helicopters

Figure 9-5. Hover taxi.

Air Taxi (100 Feet or Less)

Faster Travel

Figure 9-6. Air taxi.

Surface Taxi

Less Rotor Downwash

Figure 9-7. Surface taxi.

9-10

along the surface. Use the antitorque pedals to maintainheading and the cyclic to maintain ground track. Thecollective controls starting, stopping, and speed whiletaxiing. The higher the collective pitch, the faster thetaxi speed; however, you should not taxi faster than abrisk walk. If your helicopter is equipped with brakes,use them to help you slow down. Do not use the cyclicto control groundspeed.

During a crosswind taxi, hold the cyclic into the wind asufficient amount to eliminate any drifting movement.

COMMON ERRORS1. Improper use of cyclic.

2. Failure to use antitorque pedals for heading control.

3. Improper use of the controls during crosswindoperations.

4. Failure to maintain proper r.p.m.

NORMAL TAKEOFF FROM A HOVERA normal takeoff from a hover is an orderly transitionto forward flight and is executed to increase altitudesafely and expeditiously. During the takeoff, fly a pro-file that avoids the cross-hatched or shaded areas of theheight-velocity diagram.

TECHNIQUERefer to figure 9-8 (position 1). Bring the helicopter toa hover and make a performance check, whichincludes power, balance, and flight controls. The powercheck should include an evaluation of the amount ofexcess power available; that is, the difference betweenthe power being used to hover and the power availableat the existing altitude and temperature conditions. Thebalance condition of the helicopter is indicated by theposition of the cyclic when maintaining a stationary

hover. Wind will necessitate some cyclic deflection,but there should not be an extreme deviation fromneutral. Flight controls must move freely, and the hel-icopter should respond normally. Then visually clearthe area all around.

Start the helicopter moving by smoothly and slowly eas-ing the cyclic forward (position 2). As the helicopterstarts to move forward, increase the collective, as nec-essary, to prevent the helicopter from sinking and adjustthe throttle to maintain r.p.m. The increase in powerrequires an increase in the proper antitorque pedal tomaintain heading. Maintain a straight takeoff paththroughout the takeoff. As you accelerate through effec-tive translational lift (position 3), the helicopter beginsto climb and the nose tends to rise due to increased lift.At this point adjust the collective to obtain normal climbpower and apply enough forward cyclic to overcomethe tendency of the nose to rise. At position 4, hold anattitude that allows a smooth acceleration toward climb-ing airspeed and a commensurate gain in altitude so thatthe takeoff profile does not take you through any of thecross-hatched or shaded areas of the height-velocity diagram. As airspeed increases (position 5), the stream-lining of the fuselage reduces engine torque effect,requiring a gradual reduction of antitorque pedal pressure. As the helicopter continues to climb and accel-erate to best rate of climb, apply aft cyclic pressure toraise the nose smoothly to the normal climb attitude.

COMMON ERRORS1. Failing to use sufficient collective pitch to pre-

vent loss of altitude prior to attaining transla-tional lift.

2. Adding power too rapidly at the beginning of thetransition from hovering to forward flight withoutforward cyclic compensation, causing the helicopterto gain excessive altitude before acquiring airspeed.

Figure 9-8. The helicopter takes several positions during a normal takeoff from a hover. The numbered positions in the text referto the numbers in this illustration.

9-11

3. Assuming an extreme nose-down attitude nearthe surface in the transition from hovering toforward flight.

4. Failing to maintain a straight flight path over thesurface (ground track).

5. Failing to maintain proper airspeed during theclimb.

6. Failing to adjust the throttle to maintain properr.p.m.

NORMAL TAKEOFF FROM THESURFACENormal takeoff from the surface is used to move thehelicopter from a position on the surface into effectivetranslational lift and a normal climb using a minimumamount of power. If the surface is dusty or covered withloose snow, this technique provides the most favorablevisibility conditions and reduces the possibility ofdebris being ingested by the engine.

TECHNIQUEPlace the helicopter in a stationary position on the sur-face. Lower the collective to the full down position,and reduce the r.p.m. below operating r.p.m. Visuallyclear the area and select terrain features, or otherobjects, to aid in maintaining the desired track duringtakeoff and climb out. Increase the throttle to theproper r.p.m. and raise the collective slowly until thehelicopter is light on the skids. Hesitate momentarilyand adjust the cyclic and antitorque pedals, as neces-sary, to prevent any surface movement. Continue toapply upward collective and, as the helicopter breaksground, use the cyclic, as necessary, to begin forwardmovement as altitude is gained. Continue to acceler-ate, and as effective translational lift is attained, thehelicopter begins to climb. Adjust attitude and power,if necessary, to climb in the same manner as a takeofffrom a hover.

COMMOM ERRORS1. Departing the surface in an attitude that is too

nose-low. This situation requires the use of exces-sive power to initiate a climb.

2. Using excessive power combined with a levelattitude, which causes a vertical climb.

3. Too abrupt application of the collective whendeparting the surface, causing r.p.m. and headingcontrol errors.

CROSSWIND CONSIDERATIONS DURING TAKEOFFSIf the takeoff is made during crosswind conditions, thehelicopter is flown in a slip during the early stages of

the maneuver. [Figure 9-9] The cyclic is held into thewind a sufficient amount to maintain the desiredground track for the takeoff. The heading is maintainedwith the use of the antitorque pedals. In other words,the rotor is tilted into the wind so that the sidewardmovement of the helicopter is just enough to counter-act the crosswind effect. To prevent the nose fromturning in the direction of the rotor tilt, it is necessaryto increase the antitorque pedal pressure on the sideopposite the rotor tilt.

After approximately 50 feet of altitude is gained, makea coordinated turn into the wind to maintain the desiredground track. This is called crabbing into the wind. Thestronger the crosswind, the more you have to turn thehelicopter into the wind to maintain the desired groundtrack. [Figure 9-10]

Wind Movement

Helicopter Side Movement

Figure 9-9. During a slip, the rotor disc is tilted into the wind.

Wind Movement

Helicopter Ground TrackHelicopter

Heading

Figure 9-10. To compensate for wind drift at altitude, crab thehelicopter into the wind.

9-12

STRAIGHT-AND-LEVEL FLIGHTStraight-and-level flight is flight in which a constantaltitude and heading are maintained. The attitude of thehelicopter determines the airspeed and is controlled bythe cyclic. Altitude is primarily controlled by use of thecollective.

TECHNIQUETo maintain forward flight, the rotor tip-path plane mustbe tilted forward to obtain the necessary horizontalthrust component from the main rotor. This generallyresults in a nose-low attitude. The lower the nose, thegreater the power required to maintain altitude, and thehigher the resulting airspeed. Conversely, the greaterthe power used, the lower the nose must be to maintainaltitude. [Figure 9-11]

When in straight-and-level flight, any increase in thecollective, while holding airspeed constant, causes thehelicopter to climb. A decrease in the collective, whileholding airspeed constant, causes the helicopter todescend. A change in the collective requires a coordi-nated change of the throttle to maintain a constantr.p.m. Additionally, the antitorque pedals need to beadjusted to maintain heading and to keep the helicopterin longitudinal trim.

To increase airspeed in straight-and-level flight, applyforward pressure on the cyclic and raise the collectiveas necessary to maintain altitude. To decrease airspeed,apply rearward pressure on the cyclic and lower thecollective, as necessary, to maintain altitude.

Although the cyclic is sensitive, there is a slight delayin control reaction, and it will be necessary to antici-pate actual movement of the helicopter. When makingcyclic inputs to control the altitude or airspeed of a hel-icopter, take care not to overcontrol. If the nose of thehelicopter rises above the level-flight attitude, applyforward pressure to the cyclic to bring the nose down.If this correction is held too long, the nose drops toolow. Since the helicopter continues to change attitudemomentarily after the controls reach neutral, return the

cyclic to neutral slightly before the desired attitude isreached. This principal holds true for any cyclic input.

Since helicopters are inherently unstable, if a gust orturbulence causes the nose to drop, the nose tends tocontinue to drop instead of returning to a straight-and-level attitude as would a fixed-wing aircraft.Therefore, you must remain alert and FLY the helicop-ter at all times.

COMMON ERRORS1. Failure to properly trim the helicopter, tending to

hold antitorque pedal pressure and oppositecyclic. This is commonly called cross-controlling.

2. Failure to maintain desired airspeed.

3. Failure to hold proper control position to main-tain desired ground track.

TURNSA turn is a maneuver used to change the heading of thehelicopter. The aerodynamics of a turn were previouslydiscussed in Chapter 3—Aerodynamics of Flight.

TECHNIQUEBefore beginning any turn, the area in the direction ofthe turn must be cleared not only at the helicopter’s alti-tude, but also above and below. To enter a turn fromstraight-and-level flight, apply sideward pressure onthe cyclic in the direction the turn is to be made. This isthe only control movement needed to start the turn. Donot use the pedals to assist the turn. Use the pedals onlyto compensate for torque to keep the helicopter in lon-gitudinal trim. [Figure 9-12]

How fast the helicopter banks depends on how muchlateral cyclic pressure you apply. How far the helicop-ter banks (the steepness of the bank) depends on howlong you displace the cyclic. After establishing theproper bank angle, return the cyclic toward the neutralposition. Increase the collective and throttle to main-

Tip-Path Plane

Figure 9-11. You can maintain a straight-and-level attitude bykeeping the tip-path plane parallel to and a constant distanceabove or below the natural horizon. For any given airspeed,this distance remains the same as long as you sit in the sameposition in the same type of aircraft.

HCL

Inertia

Figure 9-12. During a level, coordinated turn, the rate of turnis commensurate with the angle of bank used, and inertia andhorizontal component of lift (HCL) are equal.

9-13

tain altitude and r.p.m. As the torque increases, increasethe proper antitorque pedal pressure to maintain longi-tudinal trim. Depending on the degree of bank, addi-tional forward cyclic pressure may be required tomaintain airspeed.

Rolling out of the turn to straight-and-level flight is thesame as the entry into the turn except that pressure onthe cyclic is applied in the opposite direction. Since thehelicopter continues to turn as long as there is any bank,start the rollout before reaching the desired heading.

The discussion on level turns is equally applicable tomaking turns while climbing or descending. The onlydifference being that the helicopter is in a climbing ordescending attitude rather than that of level flight. If asimultaneous entry is desired, merely combine thetechniques of both maneuvers—climb or descententry and turn entry. When recovering from a climbingor descending turn, the desired heading and altitude arerarely reached at the same time. If the heading isreached first, stop the turn and maintain the climb ordescent until reaching the desired altitude. On theother hand, if the altitude is reached first, establish thelevel flight attitude and continue the turn to thedesired heading.

SLIPSA slip occurs when the helicopter slides sidewaystoward the center of the turn. [Figure 9-13] It is causedby an insufficient amount of antitorque pedal in thedirection of the turn, or too much in the direction oppo-site the turn, in relation to the amount of power used. Inother words, if you hold improper antitorque pedal pres-sure, which keeps the nose from following the turn, thehelicopter slips sideways toward the center of the turn.

SKIDSA skid occurs when the helicopter slides sidewaysaway from the center of the turn. [Figure 9-14] It iscaused by too much antitorque pedal pressure in thedirection of the turn, or by too little in the direction

opposite the turn in relation to the amount of powerused. If the helicopter is forced to turn faster withincreased pedal pressure instead of by increasing thedegree of the bank, it skids sideways away from thecenter of the turn instead of flying in its normal curvedpattern.

In summary, a skid occurs when the rate of turn is toofast for the amount of bank being used, and a slip occurswhen the rate of turn is too slow for the amount of bankbeing used.

COMMON ERRORS1. Using antitorque pedal pressures for turns. This is

usually not necessary for small helicopters.

2. Slipping or skidding in the turn.

NORMAL CLIMBThe entry into a climb from a hover has already beendiscussed under “Normal Takeoff from a Hover;” there-fore, this discussion is limited to a climb entry fromcruising flight.

TECHNIQUETo enter a climb from cruising flight, apply aft cyclic toobtain the approximate climb attitude. Simultaneouslyincrease the collective and throttle to obtain climbpower and maintain r.p.m. In a counterclockwise rotorsystem, increase the left antitorque pedal pressure tocompensate for the increased torque. As the airspeedapproaches normal climb airspeed, adjust the cyclic tohold this airspeed. Throughout the maneuver, maintainclimb attitude, heading, and airspeed with the cyclic;climb power and r.p.m. with the collective and throttle;and longitudinal trim with the antitorque pedals.

To level off from a climb, start adjusting the attitude to thelevel flight attitude a few feet prior to reaching the desiredaltitude. The amount of lead depends on the rate of climbat the time of level-off (the higher the rate of climb, the

Slip

InertiaHCL

Figure 9-13. During a slip, the rate of turn is too slow for theangle of bank used, and the horizontal component of lift(HCL) exceeds inertia.

Skid

HCL Inertia

Figure 9-14. During a skid, the rate of turn is too fast for theangle of bank used, and inertia exceeds the horizontal com-ponent of lift (HCL).

9-14

more the lead). Generally, the lead is 10 percent of theclimb rate. For example, if your climb rate is 500 feet perminute, you should lead the level-off by 50 feet.

To begin the level-off, apply forward cyclic to adjustand maintain a level flight attitude, which is slightlynose low. You should maintain climb power until theairspeed approaches the desired cruising airspeed, thenlower the collective to obtain cruising power and adjustthe throttle to obtain and maintain cruising r.p.m.Throughout the level-off, maintain longitudinal trimand heading with the antitorque pedals.

COMMON ERRORS1. Failure to maintain proper power and airspeed.

2. Holding too much or too little antitorque pedal.

3. In the level-off, decreasing power before lower-ing the nose to cruising attitude.

NORMAL DESCENTA normal descent is a maneuver in which the helicop-ter loses altitude at a controlled rate in a controlledattitude.

TECHNIQUETo establish a normal descent from straight-and-levelflight at cruising airspeed, lower the collective to obtainproper power, adjust the throttle to maintain r.p.m., andincrease right antitorque pedal pressure to maintainheading in a counterclockwise rotor system, or leftpedal pressure in a clockwise system. If cruising airspeed is the same as, or slightly above descending air-speed, simultaneously apply the necessary cyclic pressure to obtain the approximate descending attitude.If cruising speed is well above descending airspeed, youcan maintain a level flight attitude until the airspeedapproaches the descending airspeed, then lower thenose to the descending attitude. Throughout the maneu-ver, maintain descending attitude and airspeed with thecyclic; descending power and r.p.m. with the collectiveand throttle; and heading with the antitorque pedals.

To level off from the descent, lead the desired altitude byapproximately 10 percent of the rate of descent. For exam-ple, a 500 feet per minute rate of descent would require a50 foot lead. At this point, increase the collective to obtaincruising power, adjust the throttle to maintain r.p.m., andincrease left antitorque pedal pressure to maintain heading(right pedal pressure in a clockwise rotor system). Adjustthe cyclic to obtain cruising airspeed and a level flight atti-tude as the desired altitude is reached.

COMMON ERRORS1. Failure to maintain constant angle of decent dur-

ing training.

2. Failure to lead the level-off sufficiently, whichresults in recovery below the desired altitude.

3. Failure to adjust antitorque pedal pressures forchanges in power.

GROUND REFERENCE MANEUVERSGround reference maneuvers are training exercisesflown to help you develop a division of attentionbetween the flight path and ground references, whilecontrolling the helicopter and watching for other air-craft in the vicinity. Prior to each maneuver, a clearingturn should be accomplished to ensure the practice areais free of conflicting traffic.

RECTANGULAR COURSEThe rectangular course is a training maneuver in whichthe ground track of the helicopter is equidistant fromall sides of a selected rectangular area on the ground.While performing the maneuver, the altitude and air-speed should be held constant. The rectangular coursehelps you to develop a recognition of a drift toward oraway from a line parallel to the intended ground track.This is helpful in recognizing drift toward or from anairport runway during the various legs of the airporttraffic pattern.

For this maneuver, pick a square or rectangular field,or an area bounded on four sides by section lines orroads, where the sides are approximately a mile inlength. The area selected should be well away fromother air traffic. Fly the maneuver approximately 600to 1,000 feet above the ground, which is the altitudeusually required for an airport traffic pattern. Youshould fly the helicopter parallel to and at a uniformdistance, about one-fourth to one-half mile, from thefield boundaries, not above the boundaries. For bestresults, position your flight path outside the fieldboundaries just far enough away that they may beeasily observed from either pilot seat by looking outthe side of the helicopter. If an attempt is made to flydirectly above the edges of the field, you will haveno usable reference points to start and complete theturns. In addition, the closer the track of the helicop-ter is to the field boundaries, the steeper the banknecessary at the turning points. Also, you should beable to see the edges of the selected field while seatedin a normal position and looking out the side of thehelicopter during either a left-hand or right-handcourse. The distance of the ground track from theedges of the field should be the same regardless ofwhether the course is flown to the left or right. Allturns should be started when your helicopter is abeamthe corners of the field boundaries. The bank nor-mally should not exceed 30°.

Although the rectangular course may be entered fromany direction, this discussion assumes entry on a

9-15

downwind heading. [Figure 9-15] As you approach thefield boundary on the downwind leg, you should beginplanning for your turn to the crosswind leg. Since youhave a tailwind on the downwind leg, the helicopter'sgroundspeed is increased (position 1). During the turnonto the crosswind leg, which is the equivalent of thebase leg in a traffic pattern, the wind causes the heli-copter to drift away from the field. To counteract thiseffect, the roll-in should be made at a fairly fast ratewith a relatively steep bank (position 2).

As the turn progresses, the tailwind componentdecreases, which decreases the groundspeed.Consequently, the bank angle and rate of turn must bereduced gradually to ensure that upon completion ofthe turn, the crosswind ground track continues to be thesame distance from the edge of the field. Upon comple-tion of the turn, the helicopter should be level andaligned with the downwind corner of the field.However, since the crosswind is now pushing youaway from the field, you must establish the proper driftcorrection by flying slightly into the wind. Therefore,the turn to crosswind should be greater than a 90°change in heading (position 3). If the turn has beenmade properly, the field boundary again appears to beone-fourth to one-half mile away. While on the cross-wind leg, the wind correction should be adjusted, as

necessary, to maintain a uniform distance from the fieldboundary (position 4).

As the next field boundary is being approached (posi-tion 5), plan the turn onto the upwind leg. Since a windcorrection angle is being held into the wind and towardthe field while on the crosswind leg, this next turnrequires a turn of less than 90°. Since the crosswindbecomes a headwind, causing the groundspeed todecrease during this turn, the bank initially must bemedium and progressively decreased as the turn pro-ceeds. To complete the turn, time the rollout so that thehelicopter becomes level at a point aligned with thecorner of the field just as the longitudinal axis of thehelicopter again becomes parallel to the field boundary(position 6). The distance from the field boundaryshould be the same as on the other sides of the field.

On the upwind leg, the wind is a headwind, whichresults in an decreased groundspeed (position 7).Consequently, enter the turn onto the next leg with afairly slow rate of roll-in, and a relatively shallow bank(position 8). As the turn progresses, gradually increasethe bank angle because the headwind component isdiminishing, resulting in an increasing groundspeed.During and after the turn onto this leg, the wind tendsto drift the helicopter toward the field boundary. To

WIND

No Crab

Start Turn At Boundary

Complete Turn At Boundary

Turn less Than 90°—Roll Out With Crab Established

Crab Into Wind

Start Turn At Boundary

Turn More Than 90°

Enter Pattern

Complete Turn At Boundary

No CrabStart Turn At Boundary

Turn More Than 90°—Roll Out With Crab Established

Complete Turn At Boundary

Crab Into Wind

Start Turn At Boundary

Turn Less Than 90°

Complete Turn At Boundary

Trac

kW

ithN

oW

ind

Cor

rect

ion

Track W

ithNo

Wind

Correction

Figure 9-15. Rectangular course. The numbered positions in the text refer to the numbers in this illustration.

9-16

compensate for the drift, the amount of turn must beless than 90° (position 9).

Again, the rollout from this turn must be such that asthe helicopter becomes level, the nose of the helicopteris turned slightly away the field and into the wind tocorrect for drift. The helicopter should again be thesame distance from the field boundary and at the samealtitude, as on other legs. Continue the crosswind leguntil the downwind leg boundary is approached (posi-tion 10). Once more you should anticipate drift andturning radius. Since drift correction was held on thecrosswind leg, it is necessary to turn greater than 90° toalign the helicopter parallel to the downwind legboundary. Start this turn with a medium bank angle,gradually increasing it to a steeper bank as the turn pro-gresses. Time the rollout to assure paralleling theboundary of the field as the helicopter becomes level(position 11).

If you have a direct headwind or tailwind on theupwind and downwind leg, drift should not be encoun-tered. However, it may be difficult to find a situationwhere the wind is blowing exactly parallel to the fieldboundaries. This makes it necessary to use a slightwind correction angle on all the legs. It is important toanticipate the turns to compensate for groundspeed,drift, and turning radius. When the wind is behind thehelicopter, the turn is faster and steeper; when it isahead of the helicopter, the turn is slower and shallower. These same techniques apply while flying inan airport traffic pattern.

S-TURNSAnother training maneuver you might use is the S-turn,which helps you correct for wind drift in turns. Thismaneuver requires turns to the left and right. The refer-ence line used, whether a road, railroad, or fence, shouldbe straight for a considerable distance and shouldextend as nearly perpendicular to the wind as possible.

The object of S-turns is to fly a pattern of two half cir-cles of equal size on opposite sides of the reference line.[Figure 9-16] The maneuver should be performed at aconstant altitude between 600 and 1,000 feet above theterrain. S-turns may be started at any point; however,during early training it may be beneficial to start on adownwind heading. Entering downwind permits theimmediate selection of the steepest bank that is desiredthroughout the maneuver. The discussion that follows isbased on choosing a reference line that is perpendicularto the wind and starting the maneuver on a downwindheading.

As the helicopter crosses the reference line, immedi-ately establish a bank. This initial bank is the steepestused throughout the maneuver since the helicopter isheaded directly downwind and the groundspeed is at its

highest. Gradually reduce the bank, as necessary, todescribe a ground track of a half circle. Time the turnso that as the rollout is completed, the helicopter iscrossing the reference line perpendicular to it and head-ing directly upwind. Immediately enter a bank in theopposite direction to begin the second half of the “S.”Since the helicopter is now on an upwind heading, thisbank (and the one just completed before crossing thereference line) is the shallowest in the maneuver.Gradually increase the bank, as necessary, to describe aground track that is a half circle identical in size to theone previously completed on the other side of the refer-ence line. The steepest bank in this turn should beattained just prior to rollout when the helicopter isapproaching the reference line nearest the downwindheading. Time the turn so that as the rollout is com-plete, the helicopter is perpendicular to the referenceline and is again heading directly downwind.

In summary, the angle of bank required at any givenpoint in the maneuver is dependent on the ground-speed. The faster the groundspeed, the steeper thebank; the slower the groundspeed, the shallower the bank. To express it another way, the more nearlythe helicopter is to a downwind heading, the steeper thebank; the more nearly it is to an upwind heading, the shallower the bank. In addition to varying the angleof bank to correct for drift in order to maintain theproper radius of turn, the helicopter must also be flownwith a drift correction angle (crab) in relation to itsground track; except of course, when it is on directupwind or downwind headings or there is no wind. Onewould normally think of the fore and aft axis of the heli-copter as being tangent to the ground track pattern ateach point. However, this is not the case. During the turnon the upwind side of the reference line (side fromwhich the wind is blowing), crab the nose of the heli-copter toward the outside of the circle. During the turnon the downwind side of the reference line (side of thereference line opposite to the direction from which thewind is blowing), crab the nose of the helicopter towardthe inside of the circle. In either case, it is obvious that

Points of Shallowest Bank

Points of Steepest Bank

WIND

Figure 9-16. S-turns across a road.

9-17

the helicopter is being crabbed into the wind just as it iswhen trying to maintain a straight ground track. Theamount of crab depends upon the wind velocity andhow nearly the helicopter is to a crosswind position.The stronger the wind, the greater the crab angle at anygiven position for a turn of a given radius. The morenearly the helicopter is to a crosswind position, thegreater the crab angle. The maximum crab angle shouldbe at the point of each half circle farthest from the reference line.

A standard radius for S-turns cannot be specified, sincethe radius depends on the airspeed of the helicopter,the velocity of the wind, and the initial bank chosenfor entry.

TURNS AROUND A POINTThis training maneuver requires you to fly constantradius turns around a preselected point on the groundusing a bank of approximately 30°, while maintaininga constant altitude. [Figure 9-17] Your objective, as inother ground reference maneuvers, is to develop theability to subconsciously control the helicopter whiledividing attention between the flight path and groundreferences, while still watching for other air traffic inthe vicinity.

The factors and principles of drift correction that areinvolved in S-turns are also applicable in this maneu-ver. As in other ground track maneuvers, a constantradius around a point will, if any wind exists, requirea constantly changing angle of bank and angles ofwind correction. The closer the helicopter is to adirect downwind heading where the groundspeed is

greatest, the steeper the bank, and the faster the rateof turn required to establish the proper wind correc-tion angle. The more nearly it is to a direct upwindheading where the groundspeed is least, the shallowerthe bank, and the slower the rate of turn required toestablish the proper wind correction angle. It follows,then, that throughout the maneuver, the bank and rateof turn must be gradually varied in proportion to thegroundspeed.

The point selected for turns around a point should beprominent and easily distinguishable, yet small enoughto present a precise reference. Isolated trees, crossroads,or other similar small landmarks are usually suitable.The point should be in an area away from communities,livestock, or groups of people on the ground to preventpossible annoyance or hazard to others. Since themaneuver is performed between 600 and 1,000 feetAGL, the area selected should also afford an opportu-nity for a safe emergency autorotation in the event itbecomes necessary.

To enter turns around a point, fly the helicopter on adownwind heading to one side of the selected pointat a distance equal to the desired radius of turn. Whenany significant wind exists, it is necessary to roll intothe initial bank at a rapid rate so that the steepestbank is attained abeam the point when the helicopteris headed directly downwind. By entering the maneu-ver while heading directly downwind, the steepestbank can be attained immediately. Thus, if a bank of30° is desired, the initial bank is 30° if the helicopteris at the correct distance from the point. Thereafter,the bank is gradually shallowed until the point isreached where the helicopter is headed directlyupwind. At this point, the bank is gradually steepeneduntil the steepest bank is again attained when head-ing downwind at the initial point of entry.

Just as S-turns require that the helicopter be turnedinto the wind in addition to varying the bank, so doturns around a point. During the downwind half of thecircle, the helicopter’s nose must be progressivelyturned toward the inside of the circle; during theupwind half, the nose must be progressively turnedtoward the outside. The downwind half of the turnaround the point may be compared to the downwindside of the S-turn, while the upwind half of the turnaround a point may be compared to the upwind sideof the S-turn.

As you become experienced in performing turnsaround a point and have a good understanding of theeffects of wind drift and varying of the bank angleand wind correction angle as required, entry into themaneuver may be from any point. When enteringthis maneuver at any point, the radius of the turn

UPP

ER HALF OF CIRCLE

DO

W

NWIND HALF OF CIRC

LE

Shallowest

Bank

Steeper Bank

Steepest

Bank

Shallower Bank

WIND

Figure 9-17. Turns around a point.

9-18

must be carefully selected, taking into account thewind velocity and groundspeed so that an excessivebank is not required later on to maintain the properground track.

COMMON ERRORS DURING GROUNDREFERENCE MANEUVERS1. Faulty entry technique.

2. Poor planning, orientation, or division of attention.

3. Uncoordinated flight control application.

4. Improper correction for wind drift.

5. An unsymmetrical ground track during S-TurnsAcross a Road.

6. Failure to maintain selected altitude or airspeed.

7. Selection of a ground reference where there is nosuitable emergency landing area within glidingdistance.

TRAFFIC PATTERNSA traffic pattern is useful to control the flow of traffic, par-ticularly at airports without operating control towers. Itaffords a measure of safety, separation, protection, andadministrative control over arriving, departing, andcircling aircraft. Due to specialized operating character-istics, airplanes and helicopters do not mix well in thesame traffic environment. At multiple-use airports,you routinely must avoid the flow of fixed-wing traf-fic. To do this, you need to be familiar with the patterns typically flown by airplanes. In addition, youshould learn how to fly these patterns in case air traf-fic control (ATC) requests that you fly a fixed-wingtraffic pattern.

A normal traffic pattern is rectangular, has five namedlegs, and a designated altitude, usually 600 to 1,000feet AGL. A pattern in which all turns are to the left iscalled a standard pattern. [Figure 9-18] The takeoff leg(item 1) normally consists of the aircraft’s flight pathafter takeoff. This leg is also called the upwind leg. Youshould turn to the crosswind leg (item 2), after passingthe departure end of the runway when you are at a safealtitude. Fly the downwind leg (item 3) parallel to therunway at the designated traffic pattern altitude anddistance from the runway. Begin the base leg (item 4)at a point selected according to other traffic and windconditions. If the wind is very strong, begin the turnsooner than normal. If the wind is light, delay the turnto base. The final approach (item 5) is the path the air-craft flies immediately prior to touchdown.

You may find variations at different localities and atairports with operating control towers. For example, aright-hand pattern may be designated to expedite the

flow of traffic when obstacles or highly populated areasmake the use of a left-hand pattern undesirable.

When approaching an airport with an operating controltower in a helicopter, it is possible to expedite traffic bystating your intentions, for example:

1. (Call sign of helicopter) Robinson 8340J.

2. (Position) 10 miles west.

3. (Request) for landing and hover to...

In order to avoid the flow of fixed-wing traffic, thetower will often clear you direct to an approach pointor to a particular runway intersection nearest yourdestination point. At uncontrolled airports, if at allpossible, you should adhere to standard practicesand patterns.

Traffic pattern entry procedures at airports with anoperating control tower are specified by the controller.At uncontrolled airports, traffic pattern altitudes andentry procedures may vary according to establishedlocal procedures. The general procedure is for you toenter the pattern at a 45° angle to the downwind legabeam the midpoint of the runway. For informationconcerning traffic pattern and landing direction, youshould utilize airport advisory service or UNICOM,when available.

The standard departure procedure when using thefixed-wing traffic pattern is usually straight-out, down-wind, or a right-hand departure. When a control toweris in operation, you can request the type of departureyou desire. In most cases, helicopter departures aremade into the wind unless obstacles or traffic dictateotherwise. At airports without an operating controltower, you must comply with the departure proceduresestablished for that airport.

Downwind Leg

Bas

eLe

g

Final Approach Leg

Takeoff Leg (Upwind)

Crossw

indLeg

Figure 9-18. A standard traffic pattern has turns to left andfive designated legs.

9-19

APPROACHESAn approach is the transition from traffic pattern alti-tude to either a hover or to the surface. The approachshould terminate at the hover altitude with the rate ofdescent and groundspeed reaching zero at the sametime. Approaches are categorized according to the angleof descent as normal, steep, or shallow. In this chapterwe will concentrate on the normal approach. Steep andshallow approaches are discussed in the next chapter.

You should use the type of approach best suited to theexisting conditions. These conditions may includeobstacles, size and surface of the landing area, densityaltitude, wind direction and speed, and weight.Regardless of the type of approach, it should alwaysbe made to a specific, predetermined landing spot.

NORMAL APPROACH TO A HOVERA normal approach uses a descent profile of between8° and 12° starting at approximately 300 feet AGL.

TECHNIQUEOn final approach, at the recommended approach airspeed and at approximately 300 feet AGL, align thehelicopter with the point of intended touchdown. [Figure 9-19] After intercepting an approach angle of 8°to 12°, begin the approach by lowering the collective sufficiently to get the helicopter decelerating anddescending down the approach angle. With the decreasein the collective, the nose tends to pitch down, requiringaft cyclic to maintain the recommended approach air-speed attitude. Adjust antitorque pedals, as necessary, tomaintain longitudinal trim. You can determine the properapproach angle by relating the point of intended touchdown to a point on the helicopter windshield. Thecollective controls the angle of approach. If the touch-down point seems to be moving up on the windshield, theangle is becoming shallower, necessitating a slightincrease in collective. If the touchdown point movesdown on the windshield, the approach angle is becomingsteeper, requiring a slight decrease in collective. Use thecyclic to control the rate of closure or how fast your aremoving toward the touchdown point. Maintain entry airspeed until the apparent groundspeed and rate of closure appear to be increasing. At this point, slowlybegin decelerating with slight aft cyclic, and smoothlylower the collective to maintain approach angle. Use thecyclic to maintain a rate of closure equivalent to a brisk walk.

At approximately 25 to 40 feet AGL, depending on wind,the helicopter begins to lose effective translational lift. Tocompensate for loss of effective translational lift, youmust increase the collective to maintain the approachangle, while maintaining the proper r.p.m. The increaseof collective pitch tends to make the nose rise, requiringforward cyclic to maintain the proper rate of closure.

As the helicopter approaches the recommended hoveraltitude, you need to increase the collective sufficientlyto maintain the hover. At the same time you need toapply aft cyclic to stop any forward movement, whilecontrolling the heading with antitorque pedals.

COMMON ERRORS1. Failing to maintain proper r.p.m. during the entire

approach.

2. Improper use of the collective in controlling theangle of descent.

3. Failing to make antitorque pedal corrections tocompensate for collective changes during theapproach.

4. Failing to simultaneously arrive at hovering alti-tude and attitude with zero groundspeed.

5. Low r.p.m. in transition to the hover at the end ofthe approach.

6. Using too much aft cyclic close to the surface,which may result in tail rotor strikes.

HHImaginary Centerline

Figure 9-19. Plan the turn to final so the helicopter rolls outon an imaginary extension of the centerline for the finalapproach path. This path should neither angle to the land-ing area, as shown by the helicopter on the left, nor requirean S-turn, as shown by the helicopter on the right.

9-20

NORMAL APPROACH TO THE SURFACEA normal approach to the surface or a no-hover landing isused if loose snow or dusty surface conditions exist.These situations could cause severely restricted visibility,or the engine could possibly ingest debris when the heli-copter comes to a hover. The approach is the same as thenormal approach to a hover; however, instead of termi-nating at a hover, continue the approach to touchdown.Touchdown should occur with the skids level, zerogroundspeed, and a rate of descent approaching zero.

TECHNIQUE:As the helicopter nears the surface, increase the collec-tive, as necessary, to cushion the landing on the sur-face, terminate in a skids-level attitude with no forwardmovement.

COMMON ERRORS1. Terminating at a hover, then making a vertical

landing.

2. Touching down with forward movement.

3. Approaching too slow, requiring the use of exces-sive power during the termination.

4. Approaching too fast, causing a hard landing.

CROSSWIND DURING APPROACHESDuring a crosswind approach, you should crab into thewind. At approximately 50 feet of altitude, use a slip toalign the fuselage with the ground track. The rotor istilted into the wind with cyclic pressure so that the sideward movement of the helicopter and wind driftcounteract each other. Maintain the heading and groundtrack with the antitorque pedals. This technique shouldbe used on any type of crosswind approach, whether it isa shallow, normal, or steep approach.

GO-AROUNDA go-around is a procedure for remaining airborne afteran intended landing is discontinued. A go-around maybe necessary when:

• Instructed by the control tower.

• Traffic conflict occurs.

A good rule of thumb to use during an approach is tomake a go-around if the helicopter is in a position fromwhich it is not safe to continue the approach. Anytimeyou feel an approach is uncomfortable, incorrect, orpotentially dangerous, abandon the approach. The deci-sion to make a go-around should be positive and initiatedbefore a critical situation develops. When the decision ismade, carry it out without hesitation. In most cases, whenyou initiate the go-around, power is at a low setting.Therefore, your first response is to increase collective totakeoff power. This movement is coordinated with thethrottle to maintain r.p.m., and the proper antitorque pedalto control heading. Then, establish a climb attitude andmaintain climb speed to go around for another approach.

AFTER LANDING AND SECURINGWhen the flight is terminated, park the helicopterwhere it will not interfere with other aircraft and notbe a hazard to people during shutdown. Rotor down-wash can cause damage to other aircraft in closeproximity, and spectators may not realize the dangeror see the rotors turning. Passengers should remain inthe helicopter with their seats belts secured until therotors have stopped turning. During the shutdownand postflight inspection, follow the manufacturer’schecklist. Any discrepancies found should be notedand, if necessary, reported to maintenance personnel.

NOISE ABATEMENT PROCEDURESThe FAA, in conjunction with airport operators andcommunity leaders, is now using noise abatementprocedures to reduce the level of noise generated byaircraft departing over neighborhoods that are nearairports. The airport authority may simply request thatyou use a designated runway, wind permitting. Youalso may be asked to restrict some of your operations,such as practicing landings, during certain time peri-ods. There are three ways to determine the noise abate-ment procedure at an airport. First, if there is a controltower on the field, they will assign the preferred noiseabatement runway or takeoff direction to you. Second,you can check the Airport/Facility Directory for infor-mation on local procedures. Third, there may be infor-mation for you to read in the pilot’s lounge, or evensigns posted next to a runway that will advise you onlocal procedures.

10-1

The maneuvers presented in this chapter require morefinesse and understanding of the helicopter and the surrounding environment. When performing thesemaneuvers, you will probably be taking your helicopterto the edge of the safe operating envelope. Therefore, ifyou are ever in doubt about the outcome of the maneuver,you should abort the mission entirely or wait for morefavorable conditions.

RECONNAISSANCE PROCEDURESAnytime you are planning to land or takeoff at an unfa-miliar site, you should gather as much information asyou can about the area. Reconnaissance techniques areways of gathering this information.

HIGH RECONNAISSANCEThe purpose of a high reconnaissance is to determinethe wind direction and speed, a point for touchdown,the suitability of the landing area, the approach anddeparture axes, obstacles and their effect on wind pat-terns, and the most suitable flight paths into and out ofthe area. When conducting a high reconnaissance, giveparticular consideration to forced landing areas in caseof an emergency.

Altitude, airspeed, and flight pattern for a high recon-naissance are governed by wind and terrain features.You must strike a balance between a reconnaissanceconducted too high and one too low. It should not beflown so low that you have to divide your attentionbetween studying the area and avoiding obstructions toflight. A high reconnaissance should be flown at an alti-tude of 300 to 500 feet above the surface. A general ruleto follow is to ensure that sufficient altitude is availableat all times to land into the wind in case of engine fail-ure. In addition, a 45° angle of observation generallyallows the best estimate of the height of barriers, thepresence of obstacles, the size of the area, and the slopeof the terrain. Always maintain safe altitudes and air-speeds, and keep a forced landing area within reachwhenever possible.

LOW RECONNAISSANCEA low reconnaissance is accomplished during theapproach to the landing area. When flying theapproach, verify what was observed in the high recon-naissance, and check for anything new that may havebeen missed at a higher altitude, such as wires, slopes,

and small crevices. If everything is alright, you cancomplete the approach to a landing. However, you mustmake the decision to land or go-around before effectivetranslational lift is lost.

If a decision is made to complete the approach, termi-nate it in a hover, so you can carefully check the landing point before lowering the helicopter to the surface. Under certain conditions, it may be desirableto continue the approach to the surface. Once the heli-copter is on the ground, maintain operating r.p.m. untilyou have checked the stability of the helicopter to besure it is in a secure and safe position.

GROUND RECONNAISSANCEPrior to departing an unfamiliar location, make adetailed analysis of the area. There are several factorsto consider during this evaluation. Besides determiningthe best departure path, you must select a route that willget your helicopter from its present position to the take-off point.

Some things to consider while formulating a takeoffplan are the aircraft load, height of obstacles, the shapeof the area, and direction of the wind. If the helicopter isheavily loaded, you must determine if there is sufficientpower to clear the obstacles. Sometimes it is better topick a path over shorter obstacles than to take offdirectly into the wind. You should also evaluate theshape of the area so that you can pick a path that willgive you the most room to maneuver and abort the take-off if necessary. Wind analysis also helps determine theroute of takeoff. The prevailing wind can be altered byobstructions on the departure path, and can significantlyaffect aircraft performance. One way to determine thewind direction is to drop some dust or grass, andobserve which way it is blowing. Keep in mind that ifthe main rotor is turning, you will need to be a sufficientdistance from the helicopter to ensure that the down-wash of the blades does not give you a false indication.

If possible, you should walk the route from the helicop-ter to the takeoff position. Evaluate obstacles that couldbe hazardous and ensure that you will have adequaterotor clearance. Once at the downwind end of the avail-able area, mark a position for takeoff so that the tail andmain rotors have sufficient clearance from any obstruc-tions behind the helicopter. Use a sturdy marker, suchas a heavy stone or log, so it does not blow away.

10-2

MAXIMUM PERFORMANCE TAKEOFFA maximum performance takeoff is used to climb at asteep angle to clear barriers in the flight path. It can beused when taking off from small areas surrounded byhigh obstacles. Before attempting a maximum performance takeoff, you must know thoroughly thecapabilities and limitations of your equipment. Youmust also consider the wind velocity, temperature, alti-tude, gross weight, center-of-gravity location, andother factors affecting your technique and the perform-ance of the helicopter.

To safely accomplish this type of takeoff, there must beenough power to hover, in order to prevent the helicop-ter from sinking back to the surface after becoming airborne. This hover power check can be used to deter-mine if there is sufficient power available to accomplishthis maneuver.

The angle of climb for a maximum performance take-off depends on existing conditions. The more criticalthe conditions, such as high density altitudes, calmwinds, and high gross weights, the shallower the angleof climb. In light or no wind conditions, it might benecessary to operate in the crosshatched or shadedareas of the height/velocity diagram during the begin-ning of this maneuver. Therefore, be aware of the calculated risk when operating in these areas. Anengine failure at a low altitude and airspeed could placethe helicopter in a dangerous position, requiring a highdegree of skill in making a safe autorotative landing.

TECHNIQUEBefore attempting a maximum performance takeoff,bring the helicopter to a hover, and determine theexcess power available by noting the differencebetween the power available and that required to hover.You should also perform a balance and flight controlcheck and note the position of the cyclic. Then positionthe helicopter into the wind and return the helicopter tothe surface. Normally, this maneuver is initiated fromthe surface. After checking the area for obstacles andother aircraft, select reference points along the takeoff

path to maintain ground track. You should also consideralternate routes in case you are not able to complete themaneuver. [Figure 10-1]

Begin the takeoff by getting the helicopter light on theskids (position 1). Pause and neutralize all aircraft move-ment. Slowly increase the collective and position thecyclic so as to break ground in a 40 knot attitude. This isapproximately the same attitude as when the helicopter islight on the skids. Continue to slowly increase the collec-tive until the maximum power available is reached. Thislarge collective movement requires a substantial increasein pedal pressure to maintain heading (position 2). Use thecyclic, as necessary, to control movement toward thedesired flight path and, therefore, climb angle during themaneuver (position 3). Maintain rotor r.p.m. at its maxi-mum, and do not allow it to decrease since you wouldprobably have to lower the collective to regain it. Maintainthese inputs until the helicopter clears the obstacle, or untilreaching 50 feet for demonstration purposes (position 4).Then, establish a normal climb attitude and reduce power(position 5). As in any maximum performance maneuver,the techniques you use affect the actual results. Smooth,coordinated inputs coupled with precise control allow thehelicopter to attain its maximum performance.

COMMON ERRORS1. Failure to consider performance data, including

height/velocity diagram.

2. Nose too low initially, causing horizontal flightrather than more vertical flight.

3. Failure to maintain maximum permissible r.p.m.

4. Abrupt control movements.

5. Failure to resume normal climb power and air-speed after clearing the obstacle.

RUNNING/ROLLING TAKEOFFA running takeoff in a skid-type helicopter or a rollingtakeoff in a wheeled helicopter is sometimes used whenconditions of load and/or density altitude prevent a sus-tained hover at normal hovering altitude. However, youshould not attempt this maneuver if you do not havesufficient power to hover, at least momentarily. If thehelicopter cannot be hovered, its performance is unpre-dictable. If the helicopter cannot be raised off the surface at all, sufficient power might not be availableto safely accomplish the maneuver. If you cannotmomentarily hover the helicopter, you must wait forconditions to improve or off-load some of the weight.

To accomplish a safe running or rolling takeoff, the sur-face area must be of sufficient length and smoothness,and there cannot be any barriers in the flight path tointerfere with a shallow climb.

For wheeled helicopters, a rolling takeoff is sometimesused to minimize the downwash created during a take-off from a hover. Figure 10-1. Maximum performance takeoff.

10-3

TECHNIQUERefer to figure 10-2. To begin the maneuver, first alignthe helicopter to the takeoff path. Next, increase thethrottle to obtain takeoff r.p.m., and increase the collec-tive smoothly until the helicopter becomes light on theskids or landing gear (position 1). Then, move thecyclic slightly forward of the neutral hovering position,and apply additional collective to start the forwardmovement (position 2). To simulate a reduced powercondition during practice, use one to two inches lessmanifold pressure, or three to five percent less torque,than that required to hover.

Maintain a straight ground track with lateral cyclic andheading with antitorque pedals until a climb is established.As effective translational lift is gained, the helicopterbecomes airborne in a fairly level attitude with little or nopitching (position 3). Maintain an altitude to take advan-tage of ground effect, and allow the airspeed to increasetoward normal climb speed. Then, follow a climb profilethat takes you through the clear area of the height/velocitydiagram (position 4). During practice maneuvers, afteryou have climbed to an altitude of 50 feet, establish thenormal climb power setting and attitude.

COMMON ERRORS

1. Failing to align heading and ground track to keepsurface friction to a minimum.

2. Attempting to become airborne before obtainingeffective translational lift.

3. Using too much forward cyclic during the surfacerun.

4. Lowering the nose too much after becoming air-borne, resulting in the helicopter settling back tothe surface.

5. Failing to remain below the recommended altitudeuntil airspeed approaches normal climb speed.

RAPID DECELERATION (QUICK STOP)In normal operations, use the rapid deceleration or quickstop maneuver to slow the helicopter rapidly and bringit to a stationary hover. The maneuver requires a highdegree of coordination of all controls. It is practiced atan altitude that permits a safe clearance between the tailrotor and the surface throughout the maneuver, espe-cially at the point where the pitch attitude is highest.The altitude at completion should be no higher than themaximum safe hovering altitude prescribed by the man-ufacturer. In selecting an altitude at which to begin themaneuver, you should take into account the overalllength of the helicopter and the height/velocity diagram.Even though the maneuver is called a rapid decelerationor quick stop, it is performed slowly and smoothly withthe primary emphasis on coordination.

TECHNIQUEDuring training always perform this maneuver into thewind. [Figure 10-3, position 1] After leveling off at analtitude between 25 and 40 feet, depending on the man-ufacturer’s recommendations, accelerate to the desiredentry speed, which is approximately 45 knots for mosttraining helicopters (position 2). The altitude youchoose should be high enough to avoid danger to thetail rotor during the flare, but low enough to stay out ofthe crosshatched or shaded areas of the height/velocitydiagram throughout the maneuver. In addition, this altitude should be low enough that you can bring thehelicopter to a hover during the recovery.

Figure 10-2. Running/rolling takeoff.

Figure 10-3. Rapid deceleration or quick stop.

10-4

At position 3, initiate the deceleration by applying aftcyclic to reduce forward speed. Simultaneously, lowerthe collective, as necessary, to counteract any climbingtendency. The timing must be exact. If you apply toolittle down collective for the amount of aft cyclicapplied, a climb results. If you apply too much downcollective, a descent results. A rapid application of aftcyclic requires an equally rapid application of downcollective. As collective pitch is lowered, apply properantitorque pedal pressure to maintain heading, andadjust the throttle to maintain r.p.m.

After attaining the desired speed (position 4), initiatethe recovery by lowering the nose and allowing the hel-icopter to descend to a normal hovering altitude in levelflight and zero groundspeed (position 5). During therecovery, increase collective pitch, as necessary, to stopthe helicopter at normal hovering altitude, adjust thethrottle to maintain r.p.m., and apply proper pedal pres-sure, as necessary, to maintain heading.

COMMON ERRORS1. Initiating the maneuver by applying down

collective.

2. Initially applying aft cyclic stick too rapidly,causing the helicopter to balloon.

3. Failing to effectively control the rate of decelera-tion to accomplish the desired results.

4. Allowing the helicopter to stop forward motionin a tail-low attitude.

5. Failing to maintain proper r.p.m.

6. Waiting too long to apply collective pitch (power)during the recovery, resulting in excessive mani-fold pressure or an over-torque situation whencollective pitch is applied rapidly.

7. Failing to maintain a safe clearance over the terrain.

8. Improper use of antitorque pedals resulting inerratic heading changes.

STEEP APPROACH TO A HOVERA steep approach is used primarily when there areobstacles in the approach path that are too high to allowa normal approach. A steep approach permits entry into

most confined areas and is sometimes used to avoidareas of turbulence around a pinnacle. An approachangle of approximately 15° is considered a steepapproach. [Figure 10-4]

TECHNIQUEOn final approach, head your helicopter into the windand align it with the intended touchdown point at therecommended approach airspeed (position 1). Whenyou intercept an approach angle of 15°, begin theapproach by lowering the collective sufficiently tostart the helicopter descending down the approachpath and decelerating (position 2). Use the properantitorque pedal for trim. Since this angle is steeperthan a normal approach angle, you need to reduce thecollective more than that required for a normalapproach. Continue to decelerate with slight aftcyclic, and smoothly lower the collective to maintainthe approach angle. As in a normal approach, reference the touchdown point on the windshield todetermine changes in approach angle. This point is ina lower position than a normal approach. Aft cyclic isrequired to decelerate sooner than a normal approach,and the rate of closure becomes apparent at a higheraltitude. Maintain the approach angle and rate ofdescent with the collective, rate of closure with thecyclic, and trim with antitorque pedals. Use a crababove 50 feet and a slip below 50 feet for any cross-wind that might be present.

Loss of effective translational lift occurs higher in asteep approach (position 3), requiring an increase in thecollective to prevent settling, and more forward cyclicto achieve the proper rate of closure. Terminate theapproach at hovering altitude above the intended land-ing point with zero groundspeed (position 4). If powerhas been properly applied during the final portion ofthe approach, very little additional power is required inthe hover.

15° Descent

Figure 10-4. Steep approach to a hover.

Balloon—Gaining an excessive amount of altitude as a result of anabrupt flare.

10-5

COMMON ERRORS

1. Failing to maintain proper r.p.m. during the entireapproach.

2. Improper use of collective in maintaining theselected angle of descent.

3. Failing to make antitorque pedal corrections tocompensate for collective pitch changes duringthe approach.

4. Slowing airspeed excessively in order to remainon the proper angle of descent.

5. Inability to determine when effective transla-tional lift is lost.

6. Failing to arrive at hovering altitude and attitude,and zero groundspeed almost simultaneously.

7. Low r.p.m. in transition to the hover at the end ofthe approach.

8. Using too much aft cyclic close to the surface,which may result in the tail rotor striking the sur-face.

SHALLOW APPROACH ANDRUNNING/ROLL-ON LANDINGUse a shallow approach and running landing when ahigh-density altitude or a high gross weight condition,or some combination thereof, is such that a normal orsteep approach cannot be made because of insufficientpower to hover. [Figure 10-5] To compensate for thislack of power, a shallow approach and running landingmakes use of translational lift until surface contact ismade. If flying a wheeled helicopter, you can also use aroll-on landing to minimize the effect of downwash.The glide angle for a shallow approach is approxi-mately 5°. Since the helicopter will be sliding or rollingto a stop during this maneuver, the landing area mustbe smooth and long enough to accomplish this task.

TECHNIQUEA shallow approach is initiated in the same manner asthe normal approach except that a shallower angle ofdescent is maintained. The power reduction to initiatethe desired angle of descent is less than that for a normalapproach since the angle of descent is less (position 1).

As you lower the collective, maintain heading withproper antitorque pedal pressure, and r.p.m. with thethrottle. Maintain approach airspeed until the apparentrate of closure appears to be increasing. Then, begin toslow the helicopter with aft cyclic (position 2).

As in normal and steep approaches, the primary controlfor the angle and rate of descent is the collective, whilethe cyclic primarily controls the groundspeed.However, there must be a coordination of all the con-trols for the maneuver to be accomplished successfully.The helicopter should arrive at the point of touchdownat or slightly above effective translational lift. Sincetranslational lift diminishes rapidly at slow airspeeds,the deceleration must be smoothly coordinated, at thesame time keeping enough lift to prevent the helicopterfrom settling abruptly.

Just prior to touchdown, place the helicopter in a levelattitude with the cyclic, and maintain heading with theantitorque pedals. Use the cyclic to keep the headingand ground track identical (position 3). Allow the helicopter to descend gently to the surface in a straight-and-level attitude, cushioning the landing with the collective. After surface contact, move the cyclicslightly forward to ensure clearance between the tailboom and the rotor disc. You should also use thecyclic to maintain the surface track. (position 4). Younormally hold the collective stationary until the heli-copter stops; however, if you want more braking action,you can lower the collective slightly. Keep in mind thatdue to the increased ground friction when you lower thecollective, the helicopter’s nose might pitch forward.Exercise caution not to correct this pitching movementwith aft cyclic since this movement could result in therotor making contact with the tailboom. During thelanding, maintain normal r.p.m. with the throttle anddirectional control with the antitorque pedals.

For wheeled helicopters, use the same technique exceptafter landing, lower the collective, neutralize the controls, and apply the brakes, as necessary, to slow thehelicopter. Do not use aft cyclic when bringing the helicopter to a stop.

COMMON ERRORS1. Assuming excessive nose-high attitude to slow

the helicopter near the surface.

2. Insufficient collective and throttle to cushionlanding.

3. Failing to add proper antitorque pedal as collec-tive is added to cushion landing, resulting in atouchdown while the helicopter is moving side-ward.

4. Failing to maintain a speed that takes advantageof effective translational lift.

5° Descent

Figure 10-5. Shallow approach and running landing.

10-6

5. Touching down at an excessive groundspeed forthe existing conditions. (Some helicopters havemaximum touchdown groundspeeds.)

6. Failing to touch down in a level attitude.

7. Failing to maintain proper r.p.m. during and aftertouchdown.

8. Poor directional control during touchdown.

SLOPE OPERATIONSPrior to conducting any slope operations, you shouldbe thoroughly familiar with the characteristics ofdynamic rollover and mast bumping, which are dis-cussed in Chapter 11—Helicopter Emergencies. Theapproach to a slope is similar to the approach to anyother landing area. During slope operations, makeallowances for wind, barriers, and forced landing sitesin case of engine failure. Since the slope may constitutean obstruction to wind passage, you should anticipateturbulence and downdrafts.

SLOPE LANDINGYou usually land a helicopter across the slope ratherthan with the slope. Landing with the helicopter facingdown the slope or downhill is not recommendedbecause of the possibility of striking the tail rotor onthe surface.

TECHNIQUERefer to figure 10-6. At the termination of theapproach, move the helicopter slowly toward the slope,being careful not to turn the tail upslope. Position thehelicopter across the slope at a stabilized hover headedinto the wind over the spot of intended landing (frame 1). Downward pressure on the collective startsthe helicopter descending. As the upslope skid touchesthe ground, hesitate momentarily in a level attitude,then apply lateral cyclic in the direction of the slope(frame 2). This holds the skid against the slope whileyou continue lowering the downslope skid with the col-lective. As you lower the collective, continue to movethe cyclic toward the slope to maintain a fixed position(frame 3). The slope must be shallow enough so you

can hold the helicopter against it with the cyclic duringthe entire landing. A slope of 5° is considered maxi-mum for normal operation of most helicopters.

You should be aware of any abnormal vibration or mastbumping that signals maximum cyclic deflection. Ifthis occurs, abandon the landing because the slope istoo steep. In most helicopters with a counterclockwiserotor system, landings can be made on steeper slopeswhen you are holding the cyclic to the right. Whenlanding on slopes using left cyclic, some cyclic inputmust be used to overcome the translating tendency. Ifwind is not a factor, you should consider the driftingtendency when determining landing direction.

After the downslope skid is on the surface, reduce thecollective to full down, and neutralize the cyclic andpedals (frame 4). Normal operating r.p.m. should bemaintained until the full weight of the helicopter is onthe landing gear. This ensures adequate r.p.m. forimmediate takeoff in case the helicopter starts slidingdown the slope. Use antitorque pedals as necessarythroughout the landing for heading control. Beforereducing the r.p.m., move the cyclic control as neces-sary to check that the helicopter is firmly on theground.

COMMON ERRORS

1. Failure to consider wind effects during theapproach and landing.

2. Failure to maintain proper r.p.m. throughout theentire maneuver.

3. Turning the tail of the helicopter into the slope.

4. Lowering the downslope skid or wheel too rapidly.

5. Applying excessive cyclic control into the slope,causing mast bumping.

SLOPE TAKEOFFA slope takeoff is basically the reverse of a slope land-ing. [Figure 10-7] Conditions that may be associatedwith the slope, such as turbulence and obstacles, must

Figure 10-6. Slope landing.

10-7

be considered during the takeoff. Planning shouldinclude suitable forced landing areas.

TECHNIQUEBegin the takeoff by increasing r.p.m. to the normalrange with the collective full down. Then, move thecyclic toward the slope (frame 1). Holding cyclictoward the slope causes the downslope skid to rise asyou slowly raise the collective (frame 2). As the skidcomes up, move the cyclic toward the neutral position.If properly coordinated, the helicopter should attain alevel attitude as the cyclic reaches the neutral position.At the same time, use antitorque pedal pressure tomaintain heading and throttle to maintain r.p.m. Withthe helicopter level and the cyclic centered, pausemomentarily to verify everything is correct, and thengradually raise the collective to complete the liftoff(frame 3).

After reaching a hover, take care to avoid hitting theground with the tail rotor. If an upslope wind exists,execute a crosswind takeoff and then make a turn intothe wind after clearing the ground with the tail rotor.

COMMON ERRORS

1. Failure to adjust cyclic control to keep the heli-copter from sliding downslope.

2. Failure to maintain proper r.p.m.

3. Holding excessive cyclic into the slope as thedownslope skid is raised.

4. Turning the tail of the helicopter into the slopeduring takeoff.

CONFINED AREA OPERATIONSA confined area is an area where the flight of the heli-copter is limited in some direction by terrain or thepresence of obstructions, natural or manmade. Forexample, a clearing in the woods, a city street, a road, abuilding roof, etc., can each be regarded as a confinedarea. Generally, takeoffs and landings should be madeinto the wind to obtain maximum airspeed with mini-mum groundspeed.

There are several things to consider when operating inconfined areas. One of the most important is maintaininga clearance between the rotors and obstacles forming theconfined area. The tail rotor deserves special considera-tion because, in some helicopters, you cannot always seeit from the cabin. This not only applies while making theapproach, but while hovering as well. Another consider-ation is that wires are especially difficult to see; however, their supporting devices, such as poles or towers, serve as an indication of their presence andapproximate height. If any wind is present, you shouldalso expect some turbulence. [Figure 10-8]

Something else for you to consider is the availability offorced landing areas during the planned approach. Youshould think about the possibility of flying from onealternate landing area to another throughout theapproach, while avoiding unfavorable areas. Alwaysleave yourself a way out in case the landing cannot becompleted or a go-around is necessary.

APPROACHA high reconnaissance should be completed before ini-tiating the confined area approach. Start the approachphase using the wind and speed to the best possibleadvantage. Keep in mind areas suitable for forced land-ing. It may be necessary to choose between an

Figure 10-7. Slope takeoff.

Wind

Figure 10-8. If the wind velocity is 10 knots or greater, youshould expect updrafts on the windward side and downdraftson the lee side of obstacles. You should plan the approachwith these factors in mind, but be ready to alter your plans ifthe wind speed or direction changes.

10-8

approach that is crosswind, but over an open area, andone directly into the wind, but over heavily wooded orextremely rough terrain where a safe forced landingwould be impossible. If these conditions exist, considerthe possibility of making the initial phase of theapproach crosswind over the open area and then turn-ing into the wind for the final portion of the approach.

Always operate the helicopter as close to its normalcapabilities as possible, taking into consideration thesituation at hand. In all confined area operations, withthe exception of the pinnacle operation, the angle ofdescent should be no steeper than necessary to clearany barrier in the approach path and still land on theselected spot. The angle of climb on takeoff should benormal, or not steeper than necessary to clear any bar-rier. Clearing a barrier by a few feet and maintainingnormal operating r.p.m., with perhaps a reserve ofpower, is better than clearing a barrier by a wide mar-gin but with a dangerously low r.p.m. and no powerreserve.

Always make the landing to a specific point and not tosome general area. This point should be located wellforward, away from the approach end of the area. Themore confined the area, the more essential it is that youland the helicopter precisely at a definite point. Keepthis point in sight during the entire final approach.

When flying a helicopter near obstructions, alwaysconsider the tail rotor. A safe angle of descent over bar-riers must be established to ensure tail rotor clearanceof all obstructions. After coming to a hover, take careto avoid turning the tail into obstructions.

TAKEOFFA confined area takeoff is considered an altitude overairspeed maneuver. Before takeoff, make a groundreconnaissance to determine the type of takeoff to beperformed, to determine the point from which the take-off should be initiated to ensure the maximum amountof available area, and finally, how to best maneuver thehelicopter from the landing point to the proposed take-off position.

If wind conditions and available area permit, the heli-copter should be brought to a hover, turned around, andhovered forward from the landing position to the take-off position. Under certain conditions, sideward flightto the takeoff position may be necessary. If rearward

flight is required to reach the takeoff position, placereference markers in front of the helicopter in such away that a ground track can be safely followed to thetakeoff position. In addition, the takeoff marker shouldbe located so that it can be seen without hoveringbeyond it.

When planning the takeoff, consider the direction ofthe wind, obstructions, and forced landing areas. Tohelp you fly up and over an obstacle, you should forman imaginary line from a point on the leading edge ofthe helicopter to the highest obstacle to be cleared. Flythis line of ascent with enough power to clear the obstacle by a safe distance. After clearing the obstacle,maintain the power setting and accelerate to the normalclimb speed. Then, reduce power to the normal climbpower setting.

COMMON ERRORS1. Failure to perform, or improper performance of, a

high or low reconnaissance.

2. Flying the approach angle at too steep or too shal-low an approach for the existing conditions.

3. Failing to maintain proper r.p.m.

4. Failure to consider emergency landing areas.

5. Failure to select a specific landing spot.

6. Failure to consider how wind and turbulencecould affect the approach.

7. Improper takeoff and climb technique for exist-ing conditions.

PINNACLE AND RIDGELINEOPERATIONSA pinnacle is an area from which the surface dropsaway steeply on all sides. A ridgeline is a long areafrom which the surface drops away steeply on one ortwo sides, such as a bluff or precipice. The absence ofobstacles does not necessarily lessen the difficulty ofpinnacle or ridgeline operations. Updrafts, downdrafts,and turbulence, together with unsuitable terrain inwhich to make a forced landing, may still presentextreme hazards.

APPROACH AND LANDINGIf you need to climb to a pinnacle or ridgeline, do it onthe upwind side, when practicable, to take advantage ofany updrafts. The approach flight path should be paral-lel to the ridgeline and into the wind as much as possi-ble. [Figure 10-9]

Load, altitude, wind conditions, and terrain featuresdetermine the angle to use in the final part of anapproach. As a general rule, the greater the winds, thesteeper the approach needs to be to avoid turbulent airand downdrafts. Groundspeed during the approach is

Altitude over Airspeed—In this type of maneuver, it is more importantto gain altitude than airspeed. However, unless operational considera-tions dictate otherwise, the crosshatched or shaded areas of theheight/velocity diagram should be avoided.

10-9

more difficult to judge because visual references arefarther away than during approaches over trees or flatterrain. If a crosswind exists, remain clear of down-drafts on the leeward or downwind side of the ridgeline. If the wind velocity makes the crosswindlanding hazardous, you may be able to make a low,coordinated turn into the wind just prior to terminatingthe approach. When making an approach to a pinnacle,avoid leeward turbulence and keep the helicopterwithin reach of a forced landing area as long as possible.

On landing, take advantage of the long axis of the areawhen wind conditions permit. Touchdown should be

made in the forward portion of the area. Always per-form a stability check, prior to reducing r.p.m., toensure the landing gear is on firm terrain that can safelysupport the weight of the helicopter.

TAKEOFFA pinnacle takeoff is an airspeed over altitude maneu-ver made from the ground or from a hover. Since pinnacles and ridgelines are generally higher than theimmediate surrounding terrain, gaining airspeed on thetakeoff is more important than gaining altitude. Thehigher the airspeed, the more rapid the departure fromslopes of the pinnacle. In addition to covering unfavor-able terrain rapidly, a higher airspeed affords a morefavorable glide angle and thus contributes to thechances of reaching a safe area in the event of a forcedlanding. If a suitable forced landing area is not avail-able, a higher airspeed also permits a more effectiveflare prior to making an autorotative landing.

On takeoff, as the helicopter moves out of groundeffect, maintain altitude and accelerate to normal climbairspeed. When normal climb speed is attained, estab-lish a normal climb attitude. Never dive the helicopterdown the slope after clearing the pinnacle.

COMMON ERRORS

1. Failure to perform, or improper performance of, ahigh or low reconnaissance.

2. Flying the approach angle at too steep or too shal-low an approach for the existing conditions.

3. Failure to maintain proper r.p.m.

4. Failure to consider emergency landing areas.

5. Failure to consider how wind and turbulencecould affect the approach and takeoff.

Figure 10-9. When flying an approach to a pinnacle or ridge-line, avoid the areas where downdrafts are present, espe-cially when excess power is limited. If you encounterdowndrafts, it may become necessary to make an immediateturn away from the pinnacle to avoid being forced into therising terrain.

Airspeed over Altitude—This means that in this maneuver, obstaclesare not a factor, and it is more important to gain airspeed than altitude.

10-10

11-1

Today helicopters are quite reliable. However emergencies do occur, whether a result of mechanicalfailure or pilot error. By having a thorough knowledgeof the helicopter and its systems, you will be able tomore readily handle the situation. In addition, byknowing the conditions that can lead to an emergency, many potential accidents can be avoided.

AUTOROTATIONIn a helicopter, an autorotation is a descending maneu-ver where the engine is disengaged from the main rotorsystem and the rotor blades are driven solely by theupward flow of air through the rotor. In other words, theengine is no longer supplying power to the main rotor.

The most common reason for an autorotation is anengine failure, but autorotations can also be performedin the event of a complete tail rotor failure, since thereis virtually no torque produced in an autorotation. Ifaltitude permits, they can also be used to recover fromsettling with power. If the engine fails, the freewheel-ing unit automatically disengages the engine from themain rotor allowing the main rotor to rotate freely.Essentially, the freewheeling unit disengages anytimethe engine r.p.m. is less than the rotor r.p.m.

At the instant of engine failure, the main rotor bladesare producing lift and thrust from their angle of attackand velocity. By immediately lowering collective pitch,which must be done in case of an engine failure, lift anddrag are reduced, and the helicopter begins an immedi-ate descent, thus producing an upward flow of airthrough the rotor system. This upward flow of airthrough the rotor provides sufficient thrust to maintainrotor r.p.m. throughout the descent. Since the tail rotoris driven by the main rotor transmission during autoro-tation, heading control is maintained as in normal flight.

Several factors affect the rate of descent in autorota-tion; density altitude, gross weight, rotor r.p.m., andairspeed. Your primary control of the rate of descent isairspeed. Higher or lower airspeeds are obtained withthe cyclic pitch control just as in normal flight. In theory, you have a choice in the angle of descentvarying from a vertical descent to maximum range,which is the minimum angle of descent. Rate of descentis high at zero airspeed and decreases to a minimum atapproximately 50 to 60 knots, depending upon the par-ticular helicopter and the factors just mentioned. As the

airspeed increases beyond that which gives minimumrate of descent, the rate of descent increases again.

When landing from an autorotation, the energy storedin the rotating blades is used to decrease the rate ofdescent and make a soft landing. A greater amount ofrotor energy is required to stop a helicopter with a highrate of descent than is required to stop a helicopter thatis descending more slowly. Therefore, autorotativedescents at very low or very high airspeeds are morecritical than those performed at the minimum rate ofdescent airspeed.

Each type of helicopter has a specific airspeed at whicha power-off glide is most efficient. The best airspeed isthe one which combines the greatest glide range withthe slowest rate of descent. The specific airspeed issomewhat different for each type of helicopter, yet certain factors affect all configurations in the samemanner. For specific autorotation airspeeds for a partic-ular helicopter, refer to the FAA-approved rotorcraftflight manual.

The specific airspeed for autorotations is establishedfor each type of helicopter on the basis of averageweather and wind conditions and normal loading.When the helicopter is operated with heavy loads inhigh density altitude or gusty wind conditions, best performance is achieved from a slightly increased air-speed in the descent. For autorotations at low densityaltitude and light loading, best performance is achievedfrom a slight decrease in normal airspeed. Followingthis general procedure of fitting airspeed to existingconditions, you can achieve approximately the sameglide angle in any set of circumstances and estimate thetouchdown point.

When making turns during an autorotation, generallyuse cyclic control only. Use of antitorque pedals toassist or speed the turn causes loss of airspeed anddownward pitching of the nose. When an autorotationis initiated, sufficient antitorque pedal pressure shouldbe used to maintain straight flight and prevent yawing.This pressure should not be changed to assist the turn.

Use collective pitch control to manage rotor r.p.m. Ifrotor r.p.m. builds too high during an autorotation, raisethe collective sufficiently to decrease r.p.m. back to the

11-2

normal operating range. If the r.p.m. begins decreasing,you have to again lower the collective. Always keepthe rotor r.p.m. within the established range for yourhelicopter. During a turn, rotor r.p.m. increases due tothe increased back cyclic control pressure, whichinduces a greater airflow through the rotor system. Ther.p.m. builds rapidly and can easily exceed the maxi-mum limit if not controlled by use of collective. Thetighter the turn and the heavier the gross weight, thehigher the r.p.m.

To initiate an autorotation, other than in a low hover,lower the collective pitch control. This holds truewhether performing a practice autorotation or in theevent of an in-flight engine failure. This reduces thepitch of the main rotor blades and allows them tocontinue turning at normal r.p.m. During practiceautorotations, maintain the r.p.m. in the green arcwith the throttle while lowering collective. Once thecollective is fully lowered, reduce engine r.p.m. bydecreasing the throttle. This causes a split of theengine and rotor r.p.m. needles.

STRAIGHT-IN AUTOROTATIONA straight-in autorotation implies an autorotation fromaltitude with no turns. The speed at touchdown and theresulting ground run depends on the rate and amount offlare. The greater the degree of flare and the longer it isheld, the slower the touchdown speed and the shorterthe ground run. The slower the speed desired at touch-down, the more accurate the timing and speed of theflare must be, especially in helicopters with low inertiarotor systems.

TECHNIQUERefer to figure 11-1 (position 1). From level flight atthe manufacturer’s recommended airspeed, between500 to 700 feet AGL, and heading into the wind,smoothly, but firmly lower the collective pitch controlto the full down position, maintaining r.p.m. in thegreen arc with throttle. Coordinate the collective move-ment with proper antitorque pedal for trim, and applyaft cyclic control to maintain proper airspeed. Once thecollective is fully lowered, decrease throttle to ensure aclean split of the needles. After splitting the needles,readjust the throttle to keep engine r.p.m. above normal idling speed, but not high enough to causerejoining of the needles. The manufacturer often recommends the proper r.p.m.

At position 2, adjust attitude with cyclic control toobtain the manufacturer’s recommended autorotationor best gliding speed. Adjust collective pitch control, asnecessary, to maintain rotor r.p.m. in the green arc. Aftcyclic movements cause an increase in rotor r.p.m.,which is then controlled by a small increase in collec-tive pitch control. Avoid a large collective pitchincrease, which results in a rapid decay of rotor r.p.m.,

and leads to “chasing the r.p.m.” Avoid looking straightdown in front of the aircraft. Continually cross-checkattitude, trim, rotor r.p.m., and airspeed.

At approximately 40 to 100 feet above the surface, orat the altitude recommended by the manufacturer (posi-tion 3), begin the flare with aft cyclic control to reduceforward airspeed and decrease the rate of descent.Maintain heading with the antitorque pedals. Care mustbe taken in the execution of the flare so that the cycliccontrol is not moved rearward so abruptly as to causethe helicopter to climb, nor should it be moved soslowly as to not arrest the descent, which may allowthe helicopter to settle so rapidly that the tail rotorstrikes the ground. When forward motion decreases tothe desired groundspeed, which is usually the slowestpossible speed (position 4), move the cyclic controlforward to place the helicopter in the proper attitudefor landing.

The altitude at this time should be approximately 8 to15 feet AGL, depending on the altitude recommendedby the manufacturer. Extreme caution should be usedto avoid an excessive nose high and tail low attitudebelow 10 feet. At this point, if a full touchdown landingis to be made, allow the helicopter to descend vertically(position 5). Increase collective pitch, as necessary, tocheck the descent and cushion the landing. Additionalantitorque pedal is required to maintain heading as col-lective pitch is raised due to the reduction in rotorr.p.m. and the resulting reduced effect of the tail rotor.Touch down in a level flight attitude.

A power recovery can be made during training in lieuof a full touchdown landing. Refer to the section onpower recoveries for the correct technique.

Figure 11-1. Straight-in autorotation.

11-3

After touchdown and after the helicopter has come to acomplete stop, lower the collective pitch to the full-down position. Do not try to stop the forward groundrun with aft cyclic, as the main rotor blades can strikethe tail boom. Rather, by lowering the collectiveslightly during the ground run, more weight is placedon the undercarriage, slowing the helicopter.

COMMON ERRORS

1. Failing to use sufficient antitorque pedal whenpower is reduced.

2. Lowering the nose too abruptly when power isreduced, thus placing the helicopter in a dive.

3. Failing to maintain proper rotor r.p.m. during the descent.

4. Application of up-collective pitch at an excessivealtitude resulting in a hard landing, loss of heading control, and possible damage to the tailrotor and to the main rotor blade stops.

5. Failing to level the helicopter.

POWER RECOVERY FROM PRACTICEAUTOROTATIONA power recovery is used to terminate practiceautorotations at a point prior to actual touchdown.After the power recovery, a landing can be made or ago-around initiated.

TECHNIQUEAt approximately 8 to 15 feet above the ground,depending upon the helicopter being used, begin tolevel the helicopter with forward cyclic control. Avoidexcessive nose high, tail low attitude below 10 feet.Just prior to achieving level attitude, with the nose stillslightly up, coordinate upward collective pitch controlwith an increase in the throttle to join the needles atoperating r.p.m. The throttle and collective pitch mustbe coordinated properly. If the throttle is increased toofast or too much, an engine overspeed can occur; ifthrottle is increased too slowly or too little in propor-tion to the increase in collective pitch, a loss of rotorr.p.m. results. Use sufficient collective pitch to stop thedescent and coordinate proper antitorque pedal pressure to maintain heading. When a landing is to bemade following the power recovery, bring the helicop-ter to a hover at normal hovering altitude and thendescend to a landing.

If a go-around is to be made, the cyclic control shouldbe moved forward to resume forward flight. In transi-tioning from a practice autorotation to a go-around,exercise care to avoid an altitude-airspeed combinationthat would place the helicopter in an unsafe area of itsheight-velocity diagram.

COMMON ERRORS

1. Initiating recovery too late, requiring a rapid appli-cation of controls, resulting in overcontrolling.

2. Failing to obtain and maintain a level attitudenear the surface.

3. Failing to coordinate throttle and collective pitchproperly, resulting in either an engine overspeedor a loss of r.p.m.

4. Failing to coordinate proper antitorque pedal withthe increase in power

AUTOROTATIONS WITH TURNSA turn, or a series of turns, can be made during anautorotation in order to land into the wind or avoidobstacles. The turn is usually made early so that theremainder of the autorotation is the same as a straightin autorotation. The most common types are 90° and180° autorotations. The technique below describes a180° autorotation.

TECHNIQUEEstablish the aircraft on downwind at recommended airspeed at 700 feet AGL, parallel to the touchdown area.In a no wind or headwind condition, establish the groundtrack approximately 200 feet away from the touchdownpoint. If a strong crosswind exists, it will be necessary tomove your downwind leg closer or farther out. Whenabeam the intended touchdown point, reduce collective, and then split the needles. Apply proper antitorque pedal and cyclic to maintain proper attitude.Cross check attitude, trim, rotor r.p.m., and airspeed.

After the descent and airspeed is established, roll into a180° turn. For training, you should initially roll into abank of a least 30°, but no more than 40°. Check yourairspeed and rotor r.p.m. Throughout the turn, it isimportant to maintain the proper airspeed and keep theaircraft in trim. Changes in the aircraft’s attitude andthe angle of bank cause a corresponding change in rotorr.p.m. Adjust the collective, as necessary, in the turn tomaintain rotor r.p.m. in the green arc.

At the 90° point, check the progress of your turn byglancing toward your landing area. Plan the second 90 degrees of turn to roll out on the centerline. If you aretoo close, decrease the bank angle; if too far out, increasethe bank angle. Keep the helicopter in trim with anti-torque pedals.

The turn should be completed and the helicopteraligned with the intended touchdown area prior to pass-ing through 100 feet AGL. If the collective pitch wasincreased to control the r.p.m., it may have to be lowered on roll out to prevent a decay in r.p.m. Makean immediate power recovery if the aircraft is not

11-4

aligned with the touchdown point, and if the rotorr.p.m. and/or airspeed is not within proper limits.

From this point, complete the procedure as if it were astraight-in autorotation.

POWER FAILURE IN A HOVERPower failures in a hover, also called hovering autoro-tations, are practiced so that you automatically makethe correct response when confronted with engine stoppage or certain other emergencies while hovering.The techniques discussed in this section refer to heli-copters with a counter-clockwise rotor system and anantitorque rotor.

TECHNIQUETo practice hovering autorotations, establish a normalhovering altitude for the particular helicopter beingused, considering load and atmospheric conditions.Keep the helicopter headed into the wind and holdmaximum allowable r.p.m.

To simulate a power failure, firmly roll the throttle intothe spring loaded override position, if applicable. Thisdisengages the driving force of the engine from therotor, thus eliminating torque effect. As the throttle isclosed, apply proper antitorque pedal to maintain head-ing. Usually, a slight amount of right cyclic control isnecessary to keep the helicopter from drifting to theleft, to compensate for the loss of tail rotor thrust.However, use cyclic control, as required, to ensure avertical descent and a level attitude. Leave the collec-tive pitch where it is on entry.

Helicopters with low inertia rotor systems will begin tosettle immediately. Keep a level attitude and ensure avertical descent with cyclic control while maintainingheading with the pedals. At approximately 1 foot abovethe surface, apply upward collective pitch control, asnecessary, to slow the descent and cushion the landing.Usually the full amount of collective pitch is required.As upward collective pitch control is applied, the throt-tle has to be held in the closed position to prevent therotor from re-engaging.

Helicopters with high inertia rotor systems will maintainaltitude momentarily after the throttle is closed. Then, asthe rotor r.p.m. decreases, the helicopter starts to settle.When the helicopter has settled to approximately 1 footabove the surface, apply upward collective pitch controlwhile holding the throttle in the closed position to slowthe descent and cushion the landing. The timing of col-lective pitch control application, and the rate at which itis applied, depends upon the particular helicopter beingused, its gross weight, and the existing atmospheric con-ditions. Cyclic control is used to maintain a level attitudeand to ensure a vertical descent. Maintain heading withantitorque pedals.

When the weight of the helicopter is entirely on theskids, cease the application of upward collective. Whenthe helicopter has come to a complete stop, lower thecollective pitch to the full down position.

The timing of the collective pitch is a most importantconsideration. If it is applied too soon, the remainingr.p.m. may not be sufficient to make a soft landing. Onthe other hand, if collective pitch control is applied toolate, surface contact may be made before sufficientblade pitch is available to cushion the landing.

COMMON ERRORS

1. Failing to use sufficient proper antitorque pedalwhen power is reduced.

2. Failing to stop all sideward or backward move-ment prior to touchdown.

3. Failing to apply up-collective pitch properly,resulting in a hard touchdown.

4. Failing to touch down in a level attitude.

5. Not rolling the throttle completely to idle.

HEIGHT/VELOCITY DIAGRAMA height/velocity (H/V) diagram, published by themanufacturer for each model of helicopter, depicts thecritical combinations of airspeed and altitude should anengine failure occur. Operating at the altitudes and air-speeds shown within the crosshatched or shaded areasof the H/V diagram may not allow enough time for thecritical transition from powered flight to autorotation.[Figure 11-2]

An engine failure in a climb after takeoff occurring insection A of the diagram is most critical. During aclimb, a helicopter is operating at higher power settingsand blade angle of attack. An engine failure at this pointcauses a rapid rotor r.p.m. decay because the upwardmovement of the helicopter must be stopped, then adescent established in order to drive the rotor. Time isalso needed to stabilize, then increase the r.p.m. to thenormal operating range. The rate of descent must reacha value that is normal for the airspeed at the moment.Since altitude is insufficient for this sequence, you endup with decaying r.p.m., an increasing sink rate, nodeceleration lift, little translational lift, and littleresponse to the application of collective pitch to cush-ion the landing.

It should be noted that, once a steady state autorotationhas been established, the H/V diagram no longerapplies. An engine failure while descending throughsection A of the diagram, is less critical, provided a safelanding area is available.

11-5

You should avoid the low altitude, high airspeed portionof the diagram (section B), because your recognition of anengine failure will most likely coincide with, or shortlyoccur after, ground contact. Even if you detect an enginefailure, there may not be sufficient time to rotate the helicopter from a nose low, high airspeed attitude to onesuitable for slowing, then landing. Additionally, the altitude loss that occurs during recognition of engine fail-ure and rotation to a landing attitude, may not leaveenough altitude to prevent the tail skid from hitting theground during the landing maneuver.

Basically, if the helicopter represented by this H/V dia-gram is above 445 feet AGL, you have enough time andaltitude to enter a steady state autorotation, regardlessof your airspeed. If the helicopter is hovering at 5 feetAGL (or less) in normal conditions and the engine fails,a safe hovering autorotation can be made. Betweenapproximately 5 feet and 445 feet AGL, however, thetransition to autorotation depends on the altitude andairspeed of the helicopter. Therefore, you shouldalways be familiar with the height/velocity diagram forthe particular model of helicopter you are flying.

THE EFFECT OF WEIGHT VERSUSDENSITY ALTITUDEThe height/velocity diagram depicts altitude and air-speed situations from which a successful autorotation

can be made. The time required, and therefore, altitudenecessary to attain a steady state autorotative descent,is dependent on the weight of the helicopter and thedensity altitude. For this reason, the H/V diagram forsome helicopter models is valid only when the helicop-ter is operated in accordance with the gross weight vs.density altitude chart. Where appropriate, this chart isfound in the rotorcraft flight manual for the particularhelicopter. [Figure 11-3]

Figure 11-3. Assuming a density altitude of 5,500 feet, theheight/velocity diagram in figure 11-2 would be valid up to agross weight of approximately 1,700 pounds. This is found byentering the graph at a density altitude of 5,500 feet (point A),then moving horizontally to the solid line (point B). Moving ver-tically to the bottom of the graph (point C), you find that with theexisting density altitude, the maximum gross weight underwhich the height/velocity diagram is applicable is 1,700 pounds.

The gross weight vs. density altitude chart is notintended as a restriction to gross weight, but as an advi-sory to the autorotative capability of the helicopter during takeoff and climb. You must realize, however,that at gross weights above those recommended by thegross weight vs. density altitude chart, the H/V diagramis not restrictive enough.

VORTEX RING STATE (SETTLING WITHPOWER)Vortex ring state describes an aerodynamic conditionwhere a helicopter may be in a vertical descent with upto maximum power applied, and little or no cyclicauthority. The term “settling with power” comes fromthe fact that helicopter keeps settling even though fullengine power is applied.

In a normal out-of-ground-effect hover, the helicopteris able to remain stationary by propelling a large massof air down through the main rotor. Some of the air isrecirculated near the tips of the blades, curling up fromthe bottom of the rotor system and rejoining the air

500

450

400

350

300

250�

200�

150�

100�

50�

0

A

B

Smooth Hard Surface. Avoid Operation in Shaded Areas.

INDICATED AIRSPEED KNOTS (CORRECTED FOR INSTRUMENT ERROR)

HE

IGH

TA

BO

VE

SU

RFA

CE

-F

EE

T

0 10 20 30 40 50 60 70 80 90 100 110 120

A B

C

7,000

6,000

5,000

4,000

3,0001,500 1,600 1,700 1,800 1,900

GROSS WEIGHT – POUNDS

DE

NS

ITY

ALT

ITU

DE

–F

EE

TFigure 11-2. By carefully studying the height/velocity diagram, you will be able to avoid the combinations of alti-tude and airspeed that may not allow you sufficient time oraltitude to enter a stabilized autorotative descent. You mightwant to refer to this diagram during the remainder of the discussion on the height/velocity diagram.

11-6

entering the rotor from the top. This phenomenon iscommon to all airfoils and is known as tip vortices. Tipvortices consume engine power but produce no usefullift. As long as the tip vortices are small, their onlyeffect is a small loss in rotor efficiency. However, whenthe helicopter begins to descend vertically, it settlesinto its own downwash, which greatly enlarges the tipvortices. In this vortex ring state, most of the powerdeveloped by the engine is wasted in accelerating theair in a doughnut pattern around the rotor.

In addition, the helicopter may descend at a rate thatexceeds the normal downward induced-flow rate of theinner blade sections. As a result, the airflow of the innerblade sections is upward relative to the disc. This pro-duces a secondary vortex ring in addition to the normaltip-vortices. The secondary vortex ring is generatedabout the point on the blade where the airflow changesfrom up to down. The result is an unsteady turbulentflow over a large area of the disc. Rotor efficiency islost even though power is still being supplied from theengine. [Figure 11-4]

A fully developed vortex ring state is characterized byan unstable condition where the helicopter experiencesuncommanded pitch and roll oscillations, has little orno cyclic authority, and achieves a descent rate, which,if allowed to develop, may approach 6,000 feet perminute. It is accompanied by increased levels of vibration.

A vortex ring state may be entered during any maneu-ver that places the main rotor in a condition of highupflow and low forward airspeed. This condition is sometimes seen during quick-stop type maneuvers orduring recoveries from autorotations. The followingcombination of conditions are likely to cause settling ina vortex ring state:

1. A vertical or nearly vertical descent of at least300 feet per minute. (Actual critical rate dependson the gross weight, r.p.m., density altitude, andother pertinent factors.)

2. The rotor system must be using some of the avail-able engine power (from 20 to 100 percent).

3. The horizontal velocity must be slower thaneffective translational lift.

Some of the situations that are conducive to a settlingwith power condition are: attempting to hover out ofground effect at altitudes above the hovering ceiling ofthe helicopter; attempting to hover out of ground effectwithout maintaining precise altitude control; or down-wind and steep power approaches in which airspeed ispermitted to drop to nearly zero.

When recovering from a settling with power condition,the tendency on the part of the pilot is to first try to stopthe descent by increasing collective pitch. However,this only results in increasing the stalled area of therotor, thus increasing the rate of descent. Since inboardportions of the blades are stalled, cyclic control is limited. Recovery is accomplished by increasing forward speed, and/or partially lowering collectivepitch. In a fully developed vortex ring state, the onlyrecovery may be to enter autorotation to break the vortex ring state. When cyclic authority is regained,you can then increase forward airspeed.

For settling with power demonstrations and training inrecognition of vortex ring state conditions, all maneu-vers should be performed at an elevation of at least1,500 feet AGL.

To enter the maneuver, reduce power below hoverpower. Hold altitude with aft cyclic until the airspeed approaches 20 knots. Then allow the sinkrate to increase to 300 feet per minute or more as theattitude is adjusted to obtain an airspeed of less than10 knots. When the aircraft begins to shudder, theapplication of additional up collective increases thevibration and sink rate.

Recovery should be initiated at the first sign of vor-tex ring state by applying forward cyclic to increaseairspeed and simultaneously reducing collective.The recovery is complete when the aircraft passesthrough effective translational lift and a normalclimb is established.

RETREATING BLADE STALLIn forward flight, the relative airflow through themain rotor disc is different on the advancing andretreating side. The relative airflow over the advanc-ing side is higher due to the forward speed of the

Figure 11-4. Vortex ring state.

11-7

helicopter, while the relative airflow on the retreat-ing side is lower. This dissymmetry of lift increasesas forward speed increases.

To generate the same amount of lift across the rotordisc, the advancing blade flaps up while the retreat-ing blade flaps down. This causes the angle of attackto decrease on the advancing blade, which reduceslift, and increase on the retreating blade, whichincreases lift. As the forward speed increases, atsome point the low blade speed on the retreatingblade, together with its high angle of attack, causes aloss of lift (stall).

Retreating blade stall is a major factor in limiting ahelicopter’s top forward speed (VNE) and can be feltdeveloping by a low frequency vibration, pitchingup of the nose, and a roll in the direction of theretreating blade. High weight, low rotor r.p.m., highdensity altitude, turbulence and/or steep, abruptturns are all conducive to retreating blade stall athigh forward airspeeds. As altitude is increased,higher blade angles are required to maintain lift at agiven airspeed. Thus, retreating blade stall isencountered at a lower forward airspeed at altitude.Most manufacturers publish charts and graphs show-ing a VNE decrease with altitude.

When recovering from a retreating blade stall condi-tion, moving the cyclic aft only worsens the stall as aft cyclic produces a flare effect, thus increasingangles of attack. Pushing forward on the cyclic also deepens the stall as the angle of attack on theretreating blade is increased. Correct recovery fromretreating blade stall requires the collective to belowered first, which reduces blade angles and thusangle of attack. Aft cyclic can then be used to slowthe helicopter.

GROUND RESONANCEGround resonance is an aerodynamic phenomenonassociated with fully-articulated rotor systems. Itdevelops when the rotor blades move out of phasewith each other and cause the rotor disc to becomeunbalanced. This condition can cause a helicopter to self-destruct in a matter of seconds. However, forthis condition to occur, the helicopter must be incontact with the ground.

If you allow your helicopter to touch down firmly onone corner (wheel type landing gear is most conducive for this) the shock is transmitted to themain rotor system. This may cause the blades tomove out of their normal relationship with eachother. This movement occurs along the drag hinge.[Figure 11-5]

Figure 11-5. Hard contact with the ground can send a shockwave to the main rotor head, resulting in the blades of athree-bladed rotor system moving from their normal 120°relationship to each other. This could result in something like122°, 122°, and 116° between blades. When one of the other landing gear strikes the surface, the unbalanced conditioncould be further aggravated.

If the r.p.m. is low, the corrective action to stop groundresonance is to close the throttle immediately and fullylower the collective to place the blades in low pitch. If ther.p.m. is in the normal operating range, you should fly thehelicopter off the ground, and allow the blades to auto-matically realign themselves. You can then make a normaltouchdown. If you lift off and allow the helicopter tofirmly re-contact the surface before the blades arerealigned, a second shock could move the blades againand aggravate the already unbalanced condition. Thiscould lead to a violent, uncontrollable oscillation.

This situation does not occur in rigid or semirigid rotorsystems, because there is no drag hinge. In addition,skid type landing gear are not as prone to ground resonance as wheel type gear.

DYNAMIC ROLLOVERA helicopter is susceptible to a lateral rolling tendency,called dynamic rollover, when lifting off the surface.For dynamic rollover to occur, some factor has to firstcause the helicopter to roll or pivot around a skid, orlanding gear wheel, until its critical rollover angle isreached. Then, beyond this point, main rotor thrust con-tinues the roll and recovery is impossible. If the criticalrollover angle is exceeded, the helicopter rolls on itsside regardless of the cyclic corrections made.

Dynamic rollover begins when the helicopter starts topivot around its skid or wheel. This can occur for avariety of reasons, including the failure to remove atiedown or skid securing device, or if the skid or wheel

122° 116°

122°

11-8

contacts a fixed object while hovering sideward, or ifthe gear is stuck in ice, soft asphalt, or mud. Dynamicrollover may also occur if you do not use the properlanding or takeoff technique or while performing slopeoperations. Whatever the cause, if the gear or skidbecomes a pivot point, dynamic rollover is possible ifyou do not use the proper corrective technique.

Once started, dynamic rollover cannot be stopped byapplication of opposite cyclic control alone. For exam-ple, the right skid contacts an object and becomes thepivot point while the helicopter starts rolling to theright. Even with full left cyclic applied, the main rotorthrust vector and its moment follows the aircraft as itcontinues rolling to the right. Quickly applying downcollective is the most effective way to stop dynamicrollover from developing. Dynamic rollover can occurin both skid and wheel equipped helicopters, and alltypes of rotor systems.

CRITICAL CONDITIONSCertain conditions reduce the critical rollover angle,thus increasing the possibility for dynamic rollover andreducing the chance for recovery. The rate of rollingmotion is also a consideration, because as the roll rateincreases, the critical rollover angle at which recoveryis still possible, is reduced. Other critical conditionsinclude operating at high gross weights with thrust (lift)approximately equal to the weight.

Refer to figure 11-6. The following conditions aremost critical for helicopters with counter-clockwiserotor rotation:

1. right side skid/wheel down, since translating ten-dency adds to the rollover force.

2. right lateral center of gravity.

3. crosswinds from the left.

4. left yaw inputs.

For helicopters with clockwise rotor rotation, the oppo-site would be true.

CYCLIC TRIMWhen maneuvering with one skid or wheel on theground, care must be taken to keep the helicopter cycliccontrol properly trimmed. For example, if a slow take-off is attempted and the cyclic is not positioned andtrimmed to account for translating tendency, the criticalrecovery angle may be exceeded in less than two sec-onds. Control can be maintained if you maintain propercyclic position and trim, and not allow the helicopter’sroll and pitch rates to become too great. You should flyyour helicopter into the air smoothly while keepingmovements of pitch, roll, and yaw small, and not allowany untrimmed cyclic pressures.

NORMAL TAKEOFFS AND LANDINGSDynamic rollover is possible even during normal take-offs and landings on relative level ground, if one wheelor skid is on the ground and thrust (lift) is approxi-mately equal to the weight of the helicopter. If the takeoff or landing is not performed properly, a roll ratecould develop around the wheel or skid that is on theground. When taking off or landing, perform themaneuver smoothly and trim the cyclic so that no pitchor roll movement rates build up, especially the roll rate.If the bank angle starts to increase to an angle ofapproximately 5 to 8°, and full corrective cyclic doesnot reduce the angle, the collective should be reducedto diminish the unstable rolling condition.

SLOPE TAKEOFFS AND LANDINGSDuring slope operations, excessive application of cycliccontrol into the slope, together with excessive collectivepitch control, can result in the downslope skid rising sufficiently to exceed lateral cyclic control limits, and anupslope rolling motion can occur. [Figure 11-7]

Pivot Point Bank Angle

Weight

Tip Path Plane Neutral Cyclic

Tip Path Plane Full Left Cyclic

Crosswind

Tail Rotor Thrust

Main Rotor Thrust

Figure 11-6. Forces acting on a helicopter with right skid onthe ground.

Tail Rotor Thrust

Slope

Horizontal

Area ofCritical Rollover

Full Opposite Cyclic Limit to Prevent Rolling Motion

F

Figure 11-7. Upslope rolling motion.

11-9

When performing slope takeoff and landing maneu-vers, follow the published procedures and keep the rollrates small. Slowly raise the downslope skid or wheelto bring the helicopter level, and then lift off. Duringlanding, first touch down on the upslope skid or wheel,then slowly lower the downslope skid or wheel usingcombined movements of cyclic and collective. If thehelicopter rolls approximately 5 to 8° to the upslopeside, decrease collective to correct the bank angle andreturn to level attitude, then start the landing procedureagain.

USE OF COLLECTIVEThe collective is more effective in controlling the rollingmotion than lateral cyclic, because it reduces the mainrotor thrust (lift). A smooth, moderate collective reduc-tion, at a rate less than approximately full up to full downin two seconds, is adequate to stop the rolling motion.Take care, however, not to dump collective at too high arate, as this may cause a main rotor blade to strike thefuselage. Additionally, if the helicopter is on a slope andthe roll starts to the upslope side, reducing collective toofast may create a high roll rate in the opposite direction.When the upslope skid/wheel hits the ground, thedynamics of the motion can cause the helicopter tobounce off the upslope skid/wheel, and the inertia cancause the helicopter to roll about the downslope groundcontact point and over on its side. [Figure 11-8]

The collective should not be pulled suddenly to get air-borne, as a large and abrupt rolling moment in theopposite direction could occur. Excessive applicationof collective can result in the upslope skid rising suffi-ciently to exceed lateral cyclic control limits. Thismovement may be uncontrollable. If the helicopter

develops a roll rate with one skid/wheel on the ground,the helicopter can roll over on its side.

PRECAUTIONSThe following lists several areas to help you avoiddynamic rollover.

1. Always practice hovering autorotations into thewind, but never when the wind is gusty or over10 knots.

2. When hovering close to fences, sprinklers,bushes, runway/taxi lights, or other obstacles thatcould catch a skid, use extreme caution.

3. Always use a two-step liftoff. Pull in just enoughcollective pitch control to be light on the skidsand feel for equilibrium, then gently lift the helicopter into the air.

4. When practicing hovering maneuvers close tothe ground, make sure you hover high enough tohave adequate skid clearance with any obsta-cles, especially when practicing sideways orrearward flight.

5. When the wind is coming from the upslope direc-tion, less lateral cyclic control will be available.

6. Tailwind conditions should be avoided when conducting slope operations.

7. When the left skid/wheel is upslope, less lateralcyclic control is available due to the translatingtendency of the tail rotor. (This is true forcounter-rotating rotor systems)

8. If passengers or cargo are loaded or unloaded, thelateral cyclic requirement changes.

9. If the helicopter utilizes interconnecting fuel linesthat allow fuel to automatically transfer from oneside of the helicopter to the other, the gravitationalflow of fuel to the downslope tank could changethe center of gravity, resulting in a differentamount of cyclic control application to obtain thesame lateral result.

10. Do not allow the cyclic limits to be reached. If thecyclic control limit is reached, further lowering ofthe collective may cause mast bumping. If thisoccurs, return to a hover and select a landing pointwith a lesser degree of slope.

11. During a takeoff from a slope, if the upslopeskid/wheel starts to leave the ground before thedownslope skid/wheel, smoothly and gently

Tail Rotor Thrust

Slope

Horizontal

Area ofCritical Rollover

Full Opposite Cyclic Limit to Prevent Rolling Motion

F

Figure 11-8. Downslope rolling motion.

11-10

lower the collective and check to see if thedownslope skid/wheel is caught on something.Under these conditions vertical ascent is the onlyacceptable method of liftoff.

12. During flight operations on a floating platform, ifthe platform is pitching/rolling while attempting toland or takeoff, the result could be dynamic rollover.

LOW G CONDITIONS AND MASTBUMPINGFor cyclic control, small helicopters depend primarilyon tilting the main rotor thrust vector to produce control moments about the aircraft center of gravity(CG), causing the helicopter to roll or pitch in thedesired direction. Pushing the cyclic control forwardabruptly from either straight-and-level flight or after aclimb can put the helicopter into a low G (weightless)flight condition. In forward flight, when a push-over isperformed, the angle of attack and thrust of the rotor isreduced, causing a low G or weightless flight condi-tion. During the low G condition, the lateral cyclic haslittle, if any, effect because the rotor thrust has beenreduced. Also, in a counter-clockwise rotor system (aclockwise system would be the reverse), there is nomain rotor thrust component to the left to counteractthe tail rotor thrust to the right, and since the tail rotoris above the CG, the tail rotor thrust causes the helicop-ter to roll rapidly to the right, If you attempt to stop theright roll by applying full left cyclic before regainingmain rotor thrust, the rotor can exceed its flappinglimits and cause structural failure of the rotor shaft dueto mast bumping, or it may allow a blade to contact theairframe. [Figure 11-9]

Since a low G condition could have disastrous results,the best way to prevent it from happening is to avoid theconditions where it might occur. This means avoidingturbulence as much as possible. If you do encounter

turbulence, slow your forward airspeed and make smallcontrol inputs. If turbulence becomes excessive, consider making a precautionary landing. To help pre-vent turbulence induced inputs, make sure your cyclicarm is properly supported. One way to accomplish thisis to brace your arm against your leg. Even if you arenot in turbulent conditions, you should avoid abruptmovement of the cyclic and collective.

If you do find yourself in a low G condition, which can be recognized by a feeling of weightlessness and an uncontrolled roll to the right, you should imme-diately and smoothly apply aft cyclic. Do not attemptto correct the rolling action with lateral cyclic. Byapplying aft cyclic, you will load the rotor system,which in turn produces thrust. Once thrust is restored,left cyclic control becomes effective, and you can rollthe helicopter to a level attitude.

LOW ROTOR RPM AND BLADE STALLAs mentioned earlier, low rotor r.p.m. during anautorotation might result in a less than successfulmaneuver. However, if you let rotor r.p.m. decay to thepoint where all the rotor blades stall, the result is usu-ally fatal, especially when it occurs at altitude. Thedanger of low rotor r.p.m. and blade stall is greatest insmall helicopters with low blade inertia. It can occurin a number of ways, such as simply rolling the throt-tle the wrong way, pulling more collective pitch thanpower available, or when operating at a high densityaltitude.

When the rotor r.p.m. drops, the blades try to maintainthe same amount of lift by increasing pitch. As thepitch increases, drag increases, which requires morepower to keep the blades turning at the proper r.p.m.When power is no longer available to maintain r.p.m.,and therefore lift, the helicopter begins to descend.This changes the relative wind and further increasesthe angle of attack. At some point the blades will stallunless r.p.m. is restored. If all blades stall, it is almostimpossible to get smooth air flowing across theblades.

Even though there is a safety factor built into most hel-icopters, anytime your rotor r.p.m. falls below the greenarc, and you have power, simultaneously add throttleand lower the collective. If you are in forward flight,gently applying aft cyclic loads up the rotor system andhelps increase rotor r.p.m. If you are without power,immediately lower the collective and apply aft cyclic.

RECOVERY FROM LOW ROTOR RPMUnder certain conditions of high weight, high tempera-ture, or high density altitude, you might get into a situation where the r.p.m. is low even though you areusing maximum throttle. This is usually the result of

Figure 11-9. In a low G condition, improper corrective actioncould lead to the main rotor hub contacting the rotor mast.The contact with the mast becomes more violent with eachsuccessive flapping motion. This, in turn, creates a greaterflapping displacement. The result could be a severely damaged rotor mast, or the main rotor system could sepa-rate from the helicopter.

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the main rotor blades having an angle of attack that hascreated so much drag that engine power is not suffi-cient to maintain or attain normal operating r.p.m.

If you are in a low r.p.m. situation, the lifting power ofthe main rotor blades can be greatly diminished. As soonas you detect a low r.p.m. condition, immediately applyadditional throttle, if available, while slightly loweringthe collective. This reduces main rotor pitch and drag. Asthe helicopter begins to settle, smoothly raise the collec-tive to stop the descent. At hovering altitude you mayhave to repeat this technique several times to regain nor-mal operating r.p.m. This technique is sometimes called“milking the collective.” When operating at altitude, thecollective may have to be lowered only once to regainrotor speed. The amount the collective can be lowereddepends on altitude. When hovering near the surface,make sure the helicopter does not contact the ground asthe collective is lowered.

Since the tail rotor is geared to the main rotor, low mainrotor r.p.m. may prevent the tail rotor from producingenough thrust to maintain directional control. If pedalcontrol is lost and the altitude is low enough that a landing can be accomplished before the turning rateincreases dangerously, slowly decrease collective pitch,maintain a level attitude with cyclic control, and land.

SYSTEM MALFUNCTIONSThe reliability and dependability record of modernhelicopters is very impressive. By following the manufacturer’s recommendations regarding periodic maintenance and inspections, you can eliminate mostsystems and equipment failures. Most malfunctions orfailures can be traced to some error on the part of thepilot; therefore, most emergencies can be averted beforethey happen. An actual emergency is a rare occurrence.

ANTITORQUE SYSTEM FAILUREAntitorque failures usually fall into two categories.One focuses on failure of the power drive portion of thetail rotor system resulting in a complete loss of anti-torque. The other category covers mechanical controlfailures where the pilot is unable to change or controltail rotor thrust even though the tail rotor may still beproviding antitorque thrust.

Tail rotor drive system failures include driveshaft fail-ures, tail rotor gearbox failures, or a complete loss ofthe tail rotor itself. In any of these cases, the loss ofantitorque normally results in an immediate yawing ofthe helicopter’s nose. The helicopter yaws to the rightin a counter-clockwise rotor system and to the left in aclockwise system. This discussion assumes a helicopter with a counter-clockwise rotor system. Theseverity of the yaw is proportionate to the amount ofpower being used and the airspeed. An antitorque failure with a high power setting at a low airspeed

results in a severe yawing to the right. At low powersettings and high airspeeds, the yaw is less severe. Highairspeeds tend to streamline the helicopter and keep itfrom spinning.

If a tail rotor failure occurs, power has to be reduced inorder to reduce main rotor torque. The techniques differ depending on whether the helicopter is in flight or in a hover, but will ultimately require an autorotation.If a complete tail rotor failure occurs while hovering,enter a hovering autorotation by rolling off the throttle. If the failure occurs in forward flight, enter a normal autorotation by lowering the collective and rolling off the throttle. If the helicopter has enough forward airspeed (close to cruising speed) whenthe failure occurs, and depending on the helicopterdesign, the vertical stabilizer may provide enough direc-tional control to allow you to maneuver the helicopter toa more desirable landing sight. Some of the yaw may becompensated for by applying slight cyclic control oppo-site the direction of yaw. This helps in directional control, but also increases drag. Care must be taken notto lose too much forward airspeed because the stream-lining effect diminishes as airspeed is reduced. Also,more altitude is required to accelerate to the correct airspeed if an autorotation is entered into at a low airspeed.

A mechanical control failure limits or prevents con-trol of tail rotor thrust and is usually caused by astuck or broken control rod or cable. While the tailrotor is still producing antitorque thrust, it cannot becontrolled by the pilot. The amount of antitorquedepends on the position where the controls jam orfail. Once again, the techniques differ depending onthe amount of tail rotor thrust, but an autorotation isgenerally not required.

LANDING—STUCK LEFT PEDALBe sure to follow the procedures and techniques outlined in the FAA-approved rotorcraft flight man-ual for the helicopter you are flying. A stuck leftpedal, such as might be experienced during takeoff orclimb conditions, results in the helicopter’s noseyawing to the left when power is reduced. Rolling offthe throttle and entering an autorotation only makesmatters worse. The landing profile for a stuck leftpedal is best described as a normal approach to amomentary hover at three to four feet above the surface. Following an analysis, make the landing. Ifthe helicopter is not turning, simply lower the helicopter to the surface. If the helicopter is turningto the right, roll the throttle toward flight idle theamount necessary to stop the turn as you land. If thehelicopter is beginning to turn left, you should beable to make the landing prior to the turn rate becoming excessive. However, if the turn ratebecomes excessive prior to the landing, simply execute a takeoff and return for another landing.

11-12

LANDING—STUCK NEUTRAL OR RIGHT PEDALThe landing profile for a stuck neutral or a stuck rightpedal is a low power approach or descent with a running or roll-on landing. The approach profile canbest be described as a steep approach with a flare at thebottom to slow the helicopter. The power should be lowenough to establish a left yaw during the descent. Theleft yaw allows a margin of safety due to the fact thatthe helicopter will turn to the right when power isapplied. This allows the momentary use of power at thebottom of the approach. As you apply power, the heli-copter rotates to the right and becomes aligned with thelanding area. At this point, roll the throttle to flight idleand make the landing. The momentary use of powerhelps stop the descent and allows additional time foryou to level the helicopter prior to closing the throttle.

If the helicopter is not yawed to the left at the conclusionof the flare, roll the throttle to flight idle and use the collective to cushion the touchdown. As with any running or roll-on landing, use the cyclic to maintain theground track. This technique results in a longer groundrun or roll than if the helicopter was yawed to the left.

UNANTICIPATED YAW / LOSS OF TAILROTOR EFFECTIVENESS (LTE)Unanticipated yaw is the occurrence of an uncom-manded yaw rate that does not subside of its ownaccord and, which, if not corrected, can result in theloss of helicopter control. This uncommanded yaw rateis referred to as loss of tail rotor effectiveness (LTE)and occurs to the right in helicopters with a counter-clockwise rotating main rotor and to the left in helicop-ters with a clockwise main rotor rotation. Again, this discussion covers a helicopter with a counter-clockwiserotor system and an antitorque rotor.

LTE is not related to an equipment or maintenance mal-function and may occur in all single-rotor helicoptersat airspeeds less than 30 knots. It is the result of the tailrotor not providing adequate thrust to maintain direc-tional control, and is usually caused by either certainwind azimuths (directions) while hovering, or by aninsufficient tail rotor thrust for a given power setting athigher altitudes.

For any given main rotor torque setting in perfectlysteady air, there is an exact amount of tail rotor thrustrequired to prevent the helicopter from yawing eitherleft or right. This is known as tail rotor trim thrust. Inorder to maintain a constant heading while hovering,you should maintain tail rotor thrust equal to trim thrust.

The required tail rotor thrust is modified by the effectsof the wind. The wind can cause an uncommanded yawby changing tail rotor effective thrust. Certain relativewind directions are more likely to cause tail rotor thrustvariations than others. Flight and wind tunnel tests

have identified three relative wind azimuth regions thatcan either singularly, or in combination, create an LTEconducive environment. These regions can overlap,and thrust variations may be more pronounced. Also,flight testing has determined that the tail rotor does notactually stall during the period. When operating inthese areas at less than 30 knots, pilot workloadincreases dramatically.

MAIN ROTOR DISC INTERFERENCE (285-315°)Refer to figure 11-10. Winds at velocities of 10 to 30knots from the left front cause the main rotor vortex to be blown into the tail rotor by the relativewind. The effect of this main rotor disc vortex causesthe tail rotor to operated in an extremely turbulent envi-ronment. During a right turn, the tail rotor experiencesa reduction of thrust as it comes into the area of themain rotor disc vortex. The reduction in tail rotor thrustcomes from the airflow changes experienced at the tailrotor as the main rotor disc vortex moves across the tailrotor disc. The effect of the main rotor disc vortex initially increases the angle of attack of the tail rotorblades, thus increasing tail rotor thrust. The increase inthe angle of attack requires that right pedal pressure beadded to reduce tail rotor thrust in order to maintain thesame rate of turn. As the main rotor vortex passes thetail rotor, the tail rotor angle of attack is reduced. Thereduction in the angle of attack causes a reduction inthrust and a right yaw acceleration begins. This accel-eration can be surprising, since you were previouslyadding right pedal to maintain the right turn rate. Thisthrust reduction occurs suddenly, and if uncorrected,develops into an uncontrollable rapid rotation about themast. When operating within this region, be aware thatthe reduction in tail rotor thrust can happen quite suddenly, and be prepared to react quickly to counterthis reduction with additional left pedal input.

Figure 11-10. Main rotor disc vortex interference.

300°

330°

285°

270°

240°

210° 150°

120°

90°

60°

30°

15 Knots

20 Knots

10 Knots

0°360°

Region of Disc Vortex Interference

315°

11-13

WEATHERCOCK STABILITY(120-240°)

In this region, the helicopter attempts to weathervaneits nose into the relative wind. [Figure 11-11] Unless aresisting pedal input is made, the helicopter starts aslow, uncommanded turn either to the right or leftdepending upon the wind direction. If the pilot allows aright yaw rate to develop and the tail of the helicoptermoves into this region, the yaw rate can accelerate rapidly. In order to avoid the onset of LTE in this downwind condition, it is imperative to maintain posi-tive control of the yaw rate and devote full attention toflying the helicopter.

Figure 11-11. Weathercock stability.

TAIL ROTOR VORTEX RING STATE (210-330°)Winds within this region cause a tail rotor vortex ringstate to develop. [Figure 11-12] The result is a non-uni-form, unsteady flow into the tail rotor. The vortex ringstate causes tail rotor thrust variations, which result inyaw deviations. The net effect of the unsteady flow isan oscillation of tail rotor thrust. Rapid and continuouspedal movements are necessary to compensate for therapid changes in tail rotor thrust when hovering in a leftcrosswind. Maintaining a precise heading in this regionis difficult, but this characteristic presents no signifi-cant problem unless corrective action is delayed.However, high pedal workload, lack of concentrationand overcontrolling can all lead to LTE.

When the tail rotor thrust being generated is less thanthe thrust required, the helicopter yaws to the right.When hovering in left crosswinds, you must concen-trated on smooth pedal coordination and not allow anuncontrolled right yaw to develop. If a right yaw rate is allowed to build, the helicopter can rotate into thewind azimuth region where weathercock stability then

accelerates the right turn rate. Pilot workload during atail rotor vortex ring state is high. Do not allow a rightyaw rate to increase.

Figure 11-12. Tail rotor vortex ring state.

LTE AT ALTITUDEAt higher altitudes, where the air is thinner, tail rotorthrust and efficiency is reduced. When operating athigh altitudes and high gross weights, especially whilehovering, the tail rotor thrust may not be sufficient tomaintain directional control and LTE can occur. In thiscase, the hovering ceiling is limited by tail rotor thrustand not necessarily power available. In these condi-tions gross weights need to be reduced and/or operations need to be limited to lower density altitudes.

REDUCING THE ONSET OF LTETo help reduce the onset of loss of tail rotor effective-ness, there are some steps you can follow.

1. Maintain maximum power-on rotor r.p.m. If themain rotor r.p.m. is allowed to decrease, the anti-torque thrust available is decreased proportionally.

2. Avoid tailwinds below an airspeed of 30 knots. Ifloss of translational lift occurs, it results in anincreased power demand and additional anti-torque pressures.

3. Avoid out of ground effect (OGE) operations andhigh power demand situations below an airspeedof 30 knots.

4. Be especially aware of wind direction and velocitywhen hovering in winds of about 8-12 knots. Thereare no strong indicators that translational lift hasbeen reduced. A loss of translational lift results inan unexpected high power demand and anincreased antitorque requirement.

Region Where Weathercock Stability Can Introduce Yaw Rates

360°0°

15 Knots

10 Knots

5 Knots

17 Knots30°

60°

90°

120°

150°180°

210°

240°

270°

300°

330°

17 Knots

15 Knots

10 Knots

5 Knots

0°

180°

150°

30°

120°

60°

90°

210°

240°

270°

300°

330°

360°

Region of Roughness Due toTail Rotor Vortex Ring State

F

11-14

5. Be aware that if a considerable amount of leftpedal is being maintained, a sufficient amount ofleft pedal may not be available to counteract anunanticipated right yaw.

6. Be alert to changing wind conditions, which maybe experienced when flying along ridge lines andaround buildings.

RECOVERY TECHNIQUEIf a sudden unanticipated right yaw occurs, the follow-ing recovery technique should be performed. Apply fullleft pedal while simultaneously moving cyclic controlforward to increase speed. If altitude permits, reducepower. As recovery is effected, adjust controls for normal forward flight.

Collective pitch reduction aids in arresting the yaw ratebut may cause an excessive rate of descent. Any large,rapid increase in collective to prevent ground or obstacle contact may further increase the yaw rate anddecrease rotor r.p.m. The decision to reduce collectivemust be based on your assessment of the altitude available for recovery.

If the rotation cannot be stopped and ground contact isimminent, an autorotation may be the best course ofaction. Maintain full left pedal until the rotation stops,then adjust to maintain heading.

MAIN DRIVE SHAFT FAILUREThe main drive shaft, located between the engine andthe main rotor gearbox, transmits engine power to themain rotor gearbox. In some helicopters, particularlythose with piston engines, a drive belt is used instead ofa drive shaft. A failure of the drive shaft or belt has thesame effect as an engine failure, because power is nolonger provided to the main rotor, and an autorotationhas to be initiated. There are a few differences, however, that need to be taken into consideration. If thedrive shaft or belt breaks, the lack of any load on theengine results in an overspeed. In this case, the throttlemust be closed in order to prevent any further damage.In some helicopters, the tail rotor drive system continues to be powered by the engine even if the maindrive shaft breaks. In this case, when the engineunloads, a tail rotor overspeed can result. If this hap-pens, close the throttle immediately and enter anautorotation.

HYDRAULIC FAILURESMost helicopters, other than smaller piston poweredhelicopters, incorporate the use of hydraulic actuatorsto overcome high control forces. A hydraulic systemconsists of actuators, also called servos, on each flightcontrol; a pump, which is usually driven by the mainrotor gearbox; and a reservoir to store the hydraulicfluid. A switch in the cockpit can turn the system off,

although it is left on under normal conditions. Apressure indicator in the cockpit may be installed tomonitor the system.

An impending hydraulic failure can be recognized by agrinding or howling noise from the pump or actuators,increased control forces and feedback, and limited control movement. The corrective action required isstated in detail in the appropriate rotorcraft flight manual. However, in most cases, airspeed needs to bereduced in order to reduce control forces. The hydraulicswitch and circuit breaker should be checked and recycled. If hydraulic power is not restored, make ashallow approach to a running or roll-on landing. Thistechnique is used because it requires less control forceand pilot workload. Additionally, the hydraulic systemshould be disabled, by either pulling the circuit breakerand/or placing the switch in the off position. The reason for this is to prevent an inadvertent restorationof hydraulic power, which may lead to overcontrollingnear the ground.

In those helicopters where the control forces are sohigh that they cannot be moved without hydraulicassistance, two or more independent hydraulic systemsmay be installed. Some helicopters use hydraulic accu-mulators to store pressure that can be used for a shorttime while in an emergency if the hydraulic pump fails.This gives you enough time to land the helicopter withnormal control.

GOVERNOR FAILUREGovernors automatically adjust engine power to main-tain rotor r.p.m. when the collective pitch is changed. Ifthe governor fails, any change in collective pitchrequires you to manually adjust the throttle to maintaincorrect r.p.m. In the event of a high side governor failure, the engine and rotor r.p.m. try to increase abovethe normal range. If the r.p.m. cannot be reduced andcontrolled with the throttle, close the throttle and enteran autorotation. If the governor fails on the low side,normal r.p.m. may not be attainable, even if the throttleis manually controlled. In this case, the collective hasto be lowered to maintain r.p.m. A running or roll-onlanding may be performed if the engine can maintainsufficient rotor r.p.m. If there is insufficient power,enter an autorotation.

ABNORMAL VIBRATIONSWith the many rotating parts found in helicopters, somevibration is inherent. You need to understand the causeand effect of helicopter vibrations because abnormalvibrations cause premature component wear and mayeven result in structural failure. With experience, youlearn what vibrations are normal versus those that areabnormal and can then decide whether continued flightis safe or not. Helicopter vibrations are categorized intolow, medium, or high frequency.

11-15

LOW FREQUENCY VIBRATIONSLow frequency vibrations (100-500 cycles per minute)usually originate from the main rotor system. Thevibration may be felt through the controls, the airframe,or a combination of both. Furthermore, the vibrationmay have a definite direction of push or thrust. It maybe vertical, lateral, horizontal, or even a combination.Normally, the direction of the vibration can be deter-mined by concentrating on the feel of the vibration,which may push you up and down, backwards and forwards, or from side to side. The direction of thevibration and whether it is felt in the controls or the airframe is an important means for the mechanic to troubleshoot the source. Some possible causes could be that the main rotor blades are out of track orbalance, damaged blades, worn bearings, dampers outof adjustment, or worn parts.

MEDIUM AND HIGH FREQUENCY VIBRATIONSMedium frequency vibrations (1,000 - 2,000 cycles perminute) and high frequency vibrations (2,000 cyclesper minute or higher) are normally associated with out-of-balance components that rotate at a high r.p.m., suchas the tail rotor, engine, cooling fans, and componentsof the drive train, including transmissions, drive shafts,bearings, pulleys, and belts. Most tail rotor vibrationscan be felt through the tail rotor pedals as long as thereare no hydraulic actuators, which usually dampen outthe vibration. Any imbalance in the tail rotor system isvery harmful, as it can cause cracks to develop and rivets to work loose. Piston engines usually produce anormal amount of high frequency vibration, which isaggravated by engine malfunctions such as spark plugfouling, incorrect magneto timing, carburetor icingand/or incorrect fuel/air mixture. Vibrations in turbineengines are often difficult to detect as these enginesoperate at a very high r.p.m.

TRACKING AND BALANCEModern equipment used for tracking and balancing themain and tail rotor blades can also be used to detectother vibrations in the helicopter. These systems useaccelerometers mounted around the helicopter to detectthe direction, frequency, and intensity of the vibration.The built-in software can then analyze the information,pinpoint the origin of the vibration, and suggest the corrective action.

FLIGHT DIVERSIONThere will probably come a time in your flight careerwhen you will not be able to make it to your destination.This can be the result of unpredictable weather conditions,a system malfunction, or poor preflight planning. In anycase, you will need to be able to safely and efficientlydivert to an alternate destination. Before any cross-country flight, check the charts for airports or suitablelanding areas along or near your route of flight. Also,check for navaids that can be used during a diversion.

Computing course, time, speed, and distance informa-tion in flight requires the same computations used during preflight planning. However, because of thelimited cockpit space, and because you must divideyour attention between flying the helicopter, makingcalculations, and scanning for other aircraft, you shouldtake advantage of all possible shortcuts and rule-of-thumb computations.

When in flight, it is rarely practical to actually plot acourse on a sectional chart and mark checkpoints anddistances. Furthermore, because an alternate airport isusually not very far from your original course, actualplotting is seldom necessary.

A course to an alternate can be measured accuratelywith a protractor or plotter, but can also be measuredwith reasonable accuracy using a straightedge and thecompass rose depicted around VOR stations. Thisapproximation can be made on the basis of a radialfrom a nearby VOR or an airway that closely parallelsthe course to your alternate. However, you mustremember that the magnetic heading associated with a VOR radial or printed airway is outbound from the station. To find the course TO the station, it may be necessary to determine the reciprocal of the indicated heading.

Distances can be determined by using a plotter, or byplacing a finger or piece of paper between the two andthen measuring the approximate distance on themileage scale at the bottom of the chart.

Before changing course to proceed to an alternate, youshould first consider the relative distance and route offlight to all suitable alternates. In addition, you shouldconsider the type of terrain along the route. If circum-stances warrant, and your helicopter is equipped withnavigational equipment, it is typically easier to navi-gate to an alternate airport that has a VOR or NDBfacility on the field.

After you select the most appropriate alternate, approx-imate the magnetic course to the alternate using a compass rose or airway on the sectional chart. If timepermits, try to start the diversion over a prominentground feature. However, in an emergency, divertpromptly toward your alternate. To complete all plotting, measuring, and computations involved beforediverting to the alternate may only aggravate an actual emergency.

Once established on course, note the time, and thenuse the winds aloft nearest to your diversion point tocalculate a heading and groundspeed. Once you havecalculated your groundspeed, determine a new arrivaltime and fuel consumption.

11-16

You must give priority to flying the helicopter whiledividing your attention between navigation and planning. When determining an altitude to use whilediverting, you should consider cloud heights, winds,terrain, and radio reception.

LOST PROCEDURESGetting lost in an aircraft is a potentially dangerous situation especially when low on fuel. Helicopters havean advantage over airplanes, as they can land almostanywhere before they run out of fuel.

If you are lost, there are some good common sense procedures to follow. If you are nowhere near or cannotsee a town or city, the first thing you should do is climb.An increase in altitude increases radio and navigationreception range, and also increases radar coverage. Ifyou are flying near a town or city, you may be able toread the name of the town on a water tower or even landto ask directions.

If your helicopter has a navigational radio, such as aVOR or ADF receiver, you can possibly determineyour position by plotting your azimuth from two ormore navigational facilities. If GPS is installed, or youhave a portable aviation GPS on board, you can use itto determine your position and the location of the nearest airport.

Communicate with any available facility using frequencies shown on the sectional chart. If you areable to communicate with a controller, you may beoffered radar vectors. Other facilities may offer direction finding (DF) assistance. To use thisprocedure, the controller will request you to holddown your transmit button for a few seconds andthen release it. The controller may ask you to change directions a few times and repeat the transmit procedure. This gives the controller enough infor-mation to plot your position and then give you vec-tors to a suitable landing sight. If your situationbecomes threatening, you can transmit your prob-lems on the emergency frequency 121.5 MHZ andset your transponder to 7700. Most facilities, andeven airliners, monitor the emergency frequency.

EMERGENCY EQUIPMENT ANDSURVIVAL GEARBoth Canada and Alaska require pilots to carry survivalgear. However, it is good common sense that any timeyou are flying over rugged and desolated terrain, con-sider carrying survival gear. Depending on the size andstorage capacity of your helicopter, the following aresome suggested items:

• Food that is not subject to deterioration due toheat or cold. There should be at least 10,000 calo-

ries for each person on board, and it should bestored in a sealed waterproof container. It shouldhave been inspected by the pilot or his represen-tative within the previous six months, and bear alabel verifying the amount and satisfactory con-dition of the contents.

• A supply of water.

• Cooking utensils.

• Matches in a waterproof container.

• A portable compass.

• An ax at least 2.5 pounds with a handle not lessthan 28 inches in length.

• A flexible saw blade or equivalent cutting tool.

• 30 feet of snare wire and instructions for use.

• Fishing equipment, including still-fishing baitand gill net with not more than a two inch mesh.

• Mosquito nets or netting and insect repellent sufficient to meet the needs of all persons aboard,when operating in areas where insects are likelyto be hazardous.

• A signaling mirror.

• At least three pyrotechnic distress signals.

• A sharp, quality jackknife or hunting knife.

• A suitable survival instruction manual.

• Flashlight with spare bulbs and batteries.

• Portable ELT with spare batteries.

Additional items when there are no trees:

• Stove with fuel or a self-contained means of pro-viding heat for cooking.

• Tent(s) to accommodate everyone on board.

Additional items for winter operations:

• Winter sleeping bags for all persons when thetemperature is expected to be below 7°C.

• Two pairs of snow shoes.

• Spare ax handle.

• Honing stone or file.

• Ice chisel.

• Snow knife or saw knife.

12-1

Attitude instrument flying in helicopters is essentiallyvisual flying with the flight instruments substituted forthe various reference points on the helicopter and thenatural horizon. Control changes, required to produce agiven attitude by reference to instruments, are identicalto those used in helicopter VFR flight, and yourthought processes are the same. Basic instrument train-ing is intended as a building block towards attaining aninstrument rating. It will also enable you to do a 180°turn in case of inadvertent incursion into instrumentmeteorological conditions (IMC).

FLIGHT INSTRUMENTSWhen flying a helicopter with reference to the flightinstruments, proper instrument interpretation is thebasis for aircraft control. Your skill, in part, depends onyour understanding of how a particular instrument orsystem functions, including its indications and limita-tions. With this knowledge, you can quickly determinewhat an instrument is telling you and translate thatinformation into a control response.

PITOT-STATIC INSTRUMENTSThe pitot-static instruments, which include the airspeedindicator, altimeter, and vertical speed indicator, oper-ate on the principle of differential air pressure. Pitotpressure, also called impact, ram, or dynamic pressure,is directed only to the airspeed indicator, while staticpressure, or ambient pressure, is directed to all threeinstruments. An alternate static source may be includedallowing you to select an alternate source of ambientpressure in the event the main port becomes blocked.[Figure 12-1]

AIRSPEED INDICATORThe airspeed indicator displays the speed of the heli-copter through the air by comparing ram air pressurefrom the pitot tube with static air pressure from thestatic port—the greater the differential, the greater thespeed. The instrument displays the result of this pres-sure differential as indicated airspeed (IAS).Manufacturers use this speed as the basis for determin-ing helicopter performance, and it may be displayed inknots, miles per hour, or both. [Figure 12-2] When anindicated airspeed is given for a particular situation,you normally use that speed without making a correc-tion for altitude or temperature. The reason no correc-

tion is needed is that an airspeed indicator and aircraftperformance are affected equally by changes in air den-sity. An indicated airspeed always yields the same performance because the indicator has, in fact, com-pensated for the change in the environment.

INSTRUMENT CHECK—During the preflight, ensurethat the pitot tube, drain hole, and static ports are unob-structed. Before liftoff, make sure the airspeed indicatoris reading zero. If there is a strong wind blowing directlyat the helicopter, the airspeed indicator may read higher

Pitot Heater Switch

Pitot Tube

Airspeed Indicator

Vertical Speed

Indicator (VSI) Altimeter

Drain Opening

Static Port

ONOFF

Alternate Static Source

ALT STATIC AIR PULL ON

Figure 12-1. Ram air pressure is supplied only to the airspeedindicator, while static pressure is used by all three instru-ments. Electrical heating elements may be installed to pre-vent ice from forming on the pitot tube. A drain opening toremove moisture is normally included.

Diaphragm

Static Air Line

Ram AirPitot Tube

Figure 12-2. Ram air pressure from the pitot tube is directedto a diaphragm inside the airspeed indicator. The airtightcase is vented to the static port. As the diaphragm expandsor contracts, a mechanical linkage moves the needle on theface of the indicator.

12-2

than zero, depending on the wind speed and direction.As you begin your takeoff, make sure the airspeed indi-cator is increasing at an appropriate rate. Keep in mind,however, that the airspeed indication might be unreli-able below a certain airspeed due to rotor downwash.

ALTIMETERThe altimeter displays altitude in feet by sensing pres-sure changes in the atmosphere. There is an adjustablebarometric scale to compensate for changes in atmos-pheric pressure. [Figure 12-3]

The basis for altimeter calibration is the InternationalStandard Atmosphere (ISA), where pressure, tempera-ture, and lapse rates have standard values. However,actual atmospheric conditions seldom match the stan-dard values. In addition, local pressure readings withina given area normally change over a period of time, andpressure frequently changes as you fly from one area toanother. As a result, altimeter indications are subject toerrors, the extent of which depends on how much thepressure, temperature, and lapse rates deviate from stan-dard, as well as how recently you have set the altimeter.The best way to minimize altimeter errors is to updatethe altimeter setting frequently. In most cases, use thecurrent altimeter setting of the nearest reporting stationalong your route of flight per regulatory requirements.

INSTRUMENT CHECK—During the preflight, ensurethat the static ports are unobstructed. Before lift-off, setthe altimeter to the current setting. If the altimeter indi-cates within 75 feet of the actual elevation, the altimeteris generally considered acceptable for use.

VERTICAL SPEED INDICATORThe vertical speed indicator (VSI) displays the rate ofclimb or descent in feet per minute (f.p.m.) by measur-ing how fast the ambient air pressure increases ordecreases as the helicopter changes altitude. Since theVSI measures only the rate at which air pressurechanges, air temperature has no effect on this instru-ment. [Figure 12-4]

There is a lag associated with the reading on the VSI,and it may take a few seconds to stabilize when show-ing rate of climb or descent. Rough control techniqueand turbulence can further extend the lag period andcause erratic and unstable rate indications. Some air-craft are equipped with an instantaneous vertical speedindicator (IVSI), which incorporates accelerometers tocompensate for the lag found in the typical VSI.

INSTRUMENT CHECK—During the preflight, ensurethat the static ports are unobstructed. Check to see thatthe VSI is indicating zero before lift-off. During takeoff,check for a positive rate of climb indication.

SYSTEM ERRORSThe pitot-static system and associated instruments areusually very reliable. Errors are generally caused whenthe pitot or static openings are blocked. This may becaused by dirt, ice formation, or insects. Check the pitotand static openings for obstructions during the preflight.It is also advisable to place covers on the pitot and staticports when the helicopter is parked on the ground.

The airspeed indicator is the only instrument affected by ablocked pitot tube. The system can become clogged in two

Aneroid Wafers

Altimeter Setting Window

Altitude Indication

Scale10,000 ft Pointer

1,000 ft Pointer

100 ft Pointer

Altimeter Setting Adjustment Knob

Crosshatch Flag A crosshatched area appears on some altimeters when displaying an altitude below 10,000 feet MSL.

Static Port

Figure 12-3. The main component of the altimeter is a stack ofsealed aneroid wafers. They expand and contract as atmos-pheric pressure from the static source changes. The mechani-cal linkage translates these changes into pointer movements onthe indicator.

Diaphragm

Direct Static PressureCalibrated

Leak

Figure 12-4. Although the sealed case and diaphragm areboth connected to the static port, the air inside the case isrestricted through a calibrated leak. When the pressures areequal, the needle reads zero. As you climb or descend, thepressure inside the diaphragm instantly changes, and theneedle registers a change in vertical direction. When thepressure differential stabilizes at a definite ratio, the needleregisters the rate of altitude change.

12-3

ways. If the ram air inlet is clogged, but the drain holeremains open, the airspeed indicator registers zero, regard-less of airspeed. If both the ram air inlet and the drain holebecome blocked, pressure in the line is trapped, and theairspeed indicator reacts like an altimeter, showing anincrease in airspeed with an increase in altitude, and adecrease in speed as altitude decreases. This occurs aslong as the static port remains unobstructed.

If the static port alone becomes blocked, the airspeedindicator continues to function, but with incorrect read-ings. When you are operating above the altitude wherethe static port became clogged, the airspeed indicatorreads lower than it should. Conversely, when operatingbelow that altitude, the indicator reads higher than thecorrect value. The amount of error is proportional tothe distance from the altitude where the static systembecame blocked. The greater the difference, the greaterthe error. With a blocked static system, the altimeterfreezes at the last altitude and the VSI freezes at zero.Both instruments are then unusable.

Some helicopters are equipped with an alternate staticsource, which may be selected in the event that the mainstatic system becomes blocked. The alternate source gen-erally vents into the cabin, where air pressures are slightlydifferent than outside pressures, so the airspeed andaltimeter usually read higher than normal. Correctioncharts may be supplied in the flight manual.

GYROSCOPIC INSTRUMENTSThe three gyroscopic instruments that are required forinstrument flight are the attitude indicator, headingindicator, and turn indicator. When installed in helicop-ters, these instruments are usually electrically powered.

Gyros are affected by two principles—rigidity in space andprecession. Rigidity in space means that once a gyro isspinning, it tends to remain in a fixed position and resistsexternal forces applied to it. This principle allows a gyro tobe used to measure changes in attitude or direction.

Precession is the tilting or turning of a gyro in response topressure. The reaction to this pressure does not occur atthe point where it was applied; rather, it occurs at a pointthat is 90° later in the direction of rotation from where thepressure was applied. This principle allows the gyro todetermine a rate of turn by sensing the amount of pres-sure created by a change in direction. Precession can alsocreate some minor errors in some instruments.

ATTITUDE INDICATORThe attitude indicator provides a substitute for the nat-ural horizon. It is the only instrument that provides animmediate and direct indication of the helicopter’spitch and bank attitude. Since most attitude indicators

installed in helicopters are electrically powered, theremay be a separate power switch, as well as a warningflag within the instrument, that indicates a loss ofpower. A caging or “quick erect” knob may beincluded, so you can stabilize the spin axis if the gyrohas tumbled. [Figure 12-5]

HEADING INDICATORThe heading indicator, which is sometimes referred toas a directional gyro (DG), senses movement aroundthe vertical axis and provides a more accurate headingreference compared to a magnetic compass, which hasa number of turning errors. [Figure 12-6].

Bank Index

Gyro

Gimbal Rotation

Roll Gimbal

Pitch Gimbal

Horizon Reference

Arm

Figure 12-5. The gyro in the attitude indicator spins in thehorizontal plane. Two mountings, or gimbals, are used sothat both pitch and roll can be sensed simultaneously. Due torigidity in space, the gyro remains in a fixed position relativeto the horizon as the case and helicopter rotate around it.

Adjustment GearsAdjustment Knob

Gimbal Rotation

Gimbal Gyro

Main Drive Gear

Compass Card Gear

Figure 12-6. A heading indicator displays headings based ona 360° azimuth, with the final zero omitted. For example, a 6represents 060°, while a 21 indicates 210°. The adjustmentknob is used to align the heading indicator with the magneticcompass.

12-4

Due to internal friction within the gyroscope, preces-sion is common in heading indicators. Precessioncauses the selected heading to drift from the set value.Some heading indicators receive a magnetic north ref-erence from a remote source and generally need noadjustment. Heading indicators that do not have thisautomatic north-seeking capability are often called“free” gyros, and require that you periodically adjustthem. You should align the heading indicator with themagnetic compass before flight and check it at 15-minute intervals during flight. When you do an in-flightalignment, be certain you are in straight-and-level,unaccelerated flight, with the magnetic compass show-ing a steady indication.

TURN INDICATORSTurn indicators show the direction and the rate of turn.A standard rate turn is 3° per second, and at this rateyou will complete a 360° turn in two minutes. A half-standard rate turn is 1.5° per second. Two types ofindicators are used to display this information. Theturn-and-slip indicator uses a needle to indicate direc-tion and turn rate. When the needle is aligned with thewhite markings, called the turn index, you are in astandard rate turn. A half-standard rate turn is indi-cated when the needle is halfway between the indexes.The turn-and-slip indicator does not indicate roll rate.The turn coordinator is similar to the turn-and-slipindicator, but the gyro is canted, which allows it tosense roll rate in addition to rate of turn. The turn coor-dinator uses a miniature aircraft to indicate direction,as well as the turn and roll rate. [Figure 12-7]

Another part of both the turn coordinator and the turn-and-slip indicator is the inclinometer. The position ofthe ball defines whether the turn is coordinated or not.The helicopter is either slipping or skidding anytimethe ball is not centered, and usually requires an adjust-ment of the antitorque pedals or angle of bank to cor-rect it. [Figure 12-8]

INSTRUMENT CHECK—During your preflight, checkto see that the inclinometer is full of fluid and has noair bubbles. The ball should also be resting at its lowestpoint. Since almost all gyroscopic instruments installedin a helicopter are electrically driven, check to see thatthe power indicators are displaying off indications.Turn the master switch on and listen to the gyros spoolup. There should be no abnormal sounds, such as agrinding sound, and the power out indicator flagsshould not be displayed. After engine start and beforeliftoff, set the direction indicator to the magnetic com-pass. During hover turns, check the heading indicatorfor proper operation and ensure that it has not pre-cessed significantly. The turn indicator should alsoindicate a turn in the correct direction. During takeoff,check the attitude indicator for proper indication andrecheck it during the first turn.

MAGNETIC COMPASSIn some helicopters, the magnetic compass is the onlydirection seeking instrument. Although the compassappears to move, it is actually mounted in such a waythat the helicopter turns about the compass card as thecard maintains its alignment with magnetic north.

COMPASS ERRORSThe magnetic compass can only give you reliabledirectional information if you understand its limitationsand inherent errors. These include magnetic variation,compass deviation, and magnetic dip.

MAGNETIC VARIATIONWhen you fly under visual flight rules, you ordinar-ily navigate by referring to charts, which are oriented

Figure 12-7. The gyros in both the turn-and-slip indicator andthe turn coordinator are mounted so that they rotate in a verti-cal plane. The gimbal in the turn coordinator is set at an angle,or canted, which means precession allows the gyro to senseboth rate of roll and rate of turn. The gimbal in the turn-and-slipindicator is horizontal. In this case, precession allows the gyroto sense only rate of turn. When the needle or miniature aircraftis aligned with the turn index, you are in a standard-rate turn.

Gyro Rotation

Gimbal Rotation

TURN-AND-SLIP INDICATOR

Gimbal

Gimbal Rotation

Gyro Rotation

Canted GyroTURN

COORDINATOR

Horizontal Gyro

Inclinometer

Figure 12-8. In a coordinated turn (instrument 1), the ball iscentered. In a skid (instrument 2), the rate of turn is too greatfor the angle of bank, and the ball moves to the outside of theturn. Conversely, in a slip (instrument 3), the rate of turn istoo small for the angle of bank, and the ball moves to theinside of the turn.

12-5

to true north. Because the aircraft compass is orientedto magnetic north, you must make allowances for thedifference between these poles in order to navigateproperly. You do this by applying a correction calledvariation to convert a true direction to a magnet direc-tion. Variation at a given point is the angular differ-ence between the true and magnetic poles. The amountof variation depends on where you are located on theearth’s surface. Isogonic lines connect points wherethe variation is equal, while the agonic line defines thepoints where the variation is zero. [Figure 12-9]

COMPASS DEVIATIONBesides the magnetic fields generated by the earth, othermagnetic fields are produced by metal and electricalaccessories within the helicopter. These magnetic fieldsdistort the earth’s magnet force and cause the compassto swing away from the correct heading. Manufacturersoften install compensating magnets within the compasshousing to reduce the effects of deviation. These mag-nets are usually adjusted while the engine is running andall electrical equipment is operating. Deviation error,however, cannot be completely eliminated; therefore, acompass correction card is mounted near the compass.The compass correction card corrects for deviation thatoccurs from one heading to the next as the lines of forceinteract at different angles.

MAGNETIC DIPMagnetic dip is the result of the vertical component ofthe earth’s magnetic field. This dip is virtually non-existent at the magnetic equator, since the lines of forceare parallel to the earth’s surface and the vertical com-ponent is minimal. As you move a compass toward thepoles, the vertical component increases, and magneticdip becomes more apparent at these higher latitudes.

Magnetic dip is responsible for compass errors duringacceleration, deceleration, and turns.

Acceleration and deceleration errors are fluctuationsin the compass during changes in speed. In the north-ern hemisphere, the compass swings toward the northduring acceleration and toward the south during decel-eration. When the speed stabilizes, the compassreturns to an accurate indication. This error is mostpronounced when you are flying on a heading of eastor west, and decreases gradually as you fly closer to anorth or south heading. The error does not occur whenyou are flying directly north or south. The memoryaid, ANDS (Accelerate North, Decelerate South) mayhelp you recall this error. In the southern hemisphere,this error occurs in the opposite direction.

Turning errors are most apparent when you are turningto or from a heading of north or south. This errorincreases as you near the poles as magnetic dip becomesmore apparent. There is no turning error when flyingnear the magnetic equator. In the northern hemisphere,when you make a turn from a northerly heading, thecompass gives an initial indication of a turn in theopposite direction. It then begins to show the turn inthe proper direction, but lags behind the actual head-ing. The amount of lag decreases as the turn continues,then disappears as the helicopter reaches a heading ofeast or west. When you make a turn from a southerlyheading, the compass gives an indication of a turn inthe correct direction, but leads the actual heading. Thiserror also disappears as the helicopter approaches aneast or west heading.

INSTRUMENT CHECK—Prior to flight, make sure thatthe compass is full of fluid. During hover turns, thecompass should swing freely and indicate known head-ings. Since that magnetic compass is required for allflight operations, the aircraft should never be flownwith a faulty compass.

INSTRUMENT FLIGHTTo achieve smooth, positive control of the helicopterduring instrument flight, you need to develop threefundamental skills. They are instrument cross-check,instrument interpretation, and aircraft control.

INSTRUMENT CROSS-CHECKCross-checking, sometimes referred to as scanning, isthe continuous and logical observation of instrumentsfor attitude and performance information. In attitudeinstrument flying, an attitude is maintained by referenceto the instruments, which produces the desired result inperformance. Due to human error, instrument error, andhelicopter performance differences in various atmos-pheric and loading conditions, it is difficult to establish an attitude and have performance remain constant for a long period of time. These variables make

A

True North Pole

Magnetic North Pole

Agonic Line

20°20°

15°

15°

10° 5°

5°0°

Isogonic Lines

17°

10°

Figure 12-9. Variation at point A in the western United Statesis 17°. Since the magnetic north pole is located to the east ofthe true north pole in relation to this point, the variation iseasterly. When the magnetic pole falls to the west of the truenorth pole, variation is westerly.

12-6

it necessary for you to constantly check the instrumentsand make appropriate changes in the helicopter’s atti-tude. The actual technique may vary depending on whatinstruments are installed and where they are installed,as well as your experience and proficiency level. Forthis discussion, we will concentrate on the six basicflight instruments discussed earlier. [Figure 12-10]

At first, you may have a tendency to cross-check rapidly, looking directly at the instruments withoutknowing exactly what information you are seeking.However, with familiarity and practice, the instrumentcross-check reveals definite trends during specificflight conditions. These trends help you control the helicopter as it makes a transition from one flight condition to another.

If you apply your full concentration to a single instrument,you will encounter a problem called “fixation.” This resultsfrom a natural human inclination to observe a specificinstrument carefully and accurately, often to the exclusionof other instruments. Fixation on a single instrument usu-ally results in poor control. For example, while performinga turn, you may have a tendency to watch only the turn-and-slip indicator instead of including other instruments in yourcross-check. This fixation on the turn-and-slip indicatoroften leads to a loss of altitude through poor pitch and bankcontrol. You should look at each instrument only longenough to understand the information it presents, then con-tinue on to the next one. Similarly, you may find yourselfplacing too much “emphasis” on a single instrument,instead of relying on a combination of instruments nec-

essary for helicopter performance information. This dif-fers from fixation in that you are using other instruments,but are giving too much attention to a particular one.

During performance of a maneuver, you may sometimesfail to anticipate significant instrument indications fol-lowing attitude changes. For example, during levelofffrom a climb or descent, you may concentrate on pitchcontrol, while forgetting about heading or roll informa-tion. This error, called “omission,” results in erraticcontrol of heading and bank.

In spite of these common errors, most pilots can adaptwell to flight by instrument reference after instructionand practice. You may find that you can control the hel-icopter more easily and precisely by instruments.

INSTRUMENT INTERPRETATIONThe flight instruments together give a picture of whatis going on. No one instrument is more important thanthe next; however, during certain maneuvers or condi-tions, those instruments that provide the most pertinentand useful information are termed primary instruments.Those which back up and supplement the primaryinstruments are termed supporting instruments. Forexample, since the attitude indicator is the only instru-ment that provides instant and direct aircraft attitudeinformation, it should be considered primary duringany change in pitch or bank attitude. After the new atti-tude is established, other instruments become primary,and the attitude indicator usually becomes the support-ing instrument.

Figure 12-10. In most situations, the cross-check pattern includes the attitude indicator between the cross-check of each of theother instruments. A typical cross-check might progress as follows: attitude indicator, altimeter, attitude indicator, VSI, attitudeindicator, heading indicator, attitude indicator, and so on.

12-7

AIRCRAFT CONTROLControlling the helicopter is the result of accuratelyinterpreting the flight instruments and translating thesereadings into correct control responses. Aircraft controlinvolves adjustment to pitch, bank, power, and trim inorder to achieve a desired flight path.

Pitch attitude control is controlling the movement ofthe helicopter about its lateral axis. After interpretingthe helicopter’s pitch attitude by reference to the pitchinstruments (attitude indicator, altimeter, airspeed indi-cator, and vertical speed indicator), cyclic controladjustments are made to affect the desired pitch atti-tude. In this chapter, the pitch attitudes illustrated areapproximate and will vary with different helicopters.

Bank attitude control is controlling the angle made bythe lateral tilt of the rotor and the natural horizon, or,the movement of the helicopter about its longitudinalaxis. After interpreting the helicopter’s bank instru-ments (attitude indicator, heading indicator, and turnindicator), cyclic control adjustments are made to attainthe desired bank attitude.

Power control is the application of collective pitch withcorresponding throttle control, where applicable. Instraight-and-level flight, changes of collective pitch aremade to correct for altitude deviations if the error ismore than 100 feet, or the airspeed is off by more than10 knots. If the error is less than that amount, use aslight cyclic climb or descent.

In order to fly a helicopter by reference to theinstruments, you should know the approximatepower settings required for your particular helicopterin various load configurations and flight conditions.

Trim, in helicopters, refers to the use of the cyclic center-ing button, if the helicopter is so equipped, to relieve allpossible cyclic pressures. Trim also refers to the use ofpedal adjustment to center the ball of the turn indicator.Pedal trim is required during all power changes.

The proper adjustment of collective pitch and cyclicfriction helps you relax during instrument flight.Friction should be adjusted to minimize overcontrol-ling and to prevent creeping, but not applied to such adegree that control movement is limited. In addition,many helicopters equipped for instrument flight con-tain stability augmentation systems or an autopilot tohelp relieve pilot workload.

STRAIGHT-AND-LEVEL FLIGHTStraight-and-level unaccelerated flight consists ofmaintaining the desired altitude, heading, airspeed, andpedal trim.

PITCH CONTROLThe pitch attitude of a helicopter is the angular relationof its longitudinal axis and the natural horizon. If avail-able, the attitude indicator is used to establish thedesired pitch attitude. In level flight, pitch attitudevaries with airspeed and center of gravity. At a constantaltitude and a stabilized airspeed, the pitch attitude isapproximately level. [Figure 12-11]

PITCH CONTRPITCH CONTROLOLPITCH CONTROL

Figure 12-11. The flight instruments for pitch control are the airspeed indicator, attitude indicator, altimeter, and verticalspeed indicator.

12-8

ATTITUDE INDICATORThe attitude indicator gives a direct indication of thepitch attitude of the helicopter. In visual flight, youattain the desired pitch attitude by using the cyclic toraise and lower the nose of the helicopter in relation tothe natural horizon. During instrument flight, you fol-low exactly the same procedure in raising or loweringthe miniature aircraft in relation to the horizon bar.

You may note some delay between control applicationand resultant instrument change. This is the normalcontrol lag in the helicopter and should not be confusedwith instrument lag. The attitude indicator may showsmall misrepresentations of pitch attitude duringmaneuvers involving acceleration, deceleration, orturns. This precession error can be detected quickly bycross-checking the other pitch instruments.

If the miniature aircraft is properly adjusted on theground, it may not require readjustment in flight. If theminiature aircraft is not on the horizon bar after level-off at normal cruising airspeed, adjust it as necessarywhile maintaining level flight with the other pitchinstruments. Once the miniature aircraft has beenadjusted in level flight at normal cruising airspeed,leave it unchanged so it will give an accurate picture ofpitch attitude at all times.

When making initial pitch attitude corrections to main-tain altitude, the changes of attitude should be smalland smoothly applied. The initial movement of thehorizon bar should not exceed one bar width high orlow. [Figure 12-12] If a further change is required, anadditional correction of one-half bar normally correctsany deviation from the desired altitude. This one and

one-half bar correction is normally the maximum pitchattitude correction from level flight attitude. After youhave made the correction, cross-check the other pitchinstruments to determine whether the pitch attitudechange is sufficient. If more correction is needed toreturn to altitude, or if the airspeed varies more than 10knots from that desired, adjust the power.

ALTIMETERThe altimeter gives an indirect indication of the pitchattitude of the helicopter in straight-and-level flight.Since the altitude should remain constant in levelflight, deviation from the desired altitude shows a needfor a change in pitch attitude, and if necessary, power.When losing altitude, raise the pitch attitude and, ifnecessary, add power. When gaining altitude, lower thepitch attitude and, if necessary, reduce power.

The rate at which the altimeter moves helps in deter-mining pitch attitude. A very slow movement of thealtimeter indicates a small deviation from the desiredpitch attitude, while a fast movement of the altimeterindicates a large deviation from the desired pitch atti-tude. Make any corrective action promptly, with smallcontrol changes. Also, remember that movement of thealtimeter should always be corrected by two distinctchanges. The first is a change of attitude to stop thealtimeter; and the second, a change of attitude toreturn smoothly to the desired altitude. If the altitudeand airspeed are more than 100 feet and 10 knots low,respectively, apply power along with an increase ofpitch attitude. If the altitude and airspeed are high bymore than 100 feet and 10 knots, reduce power andlower the pitch attitude.

There is a small lag in the movement of the altimeter;however, for all practical purposes, consider that thealtimeter gives an immediate indication of a change, ora need for change in pitch attitude.

Since the altimeter provides the most pertinent infor-mation regarding pitch in level flight, it is consideredprimary for pitch.

VERTICAL SPEED INDICATORThe vertical speed indicator gives an indirect indicationof the pitch attitude of the helicopter and should be usedin conjunction with the other pitch instruments to attaina high degree of accuracy and precision. The instrumentindicates zero when in level flight. Any movement ofthe needle from the zero position shows a need for animmediate change in pitch attitude to return it to zero.Always use the vertical speed indicator in conjunctionwith the altimeter in level flight. If a movement of thevertical speed indicator is detected, immediately use theproper corrective measures to return it to zero. If thecorrection is made promptly, there is usually little or nochange in altitude. If you do not zero the needle of the

Figure 12-12. The initial pitch correction at normal cruise isone bar width.

12-9

vertical speed indicator immediately, the results willshow on the altimeter as a gain or loss of altitude.

The initial movement of the vertical speed needle isinstantaneous and indicates the trend of the verticalmovement of the helicopter. It must be realized thata period of time is necessary for the vertical speedindicator to reach its maximum point of deflectionafter a correction has been made. This time elementis commonly referred to as “lag.” The lag is directlyproportional to the speed and magnitude of the pitchchange. If you employ smooth control techniquesand make small adjustments in pitch attitude, lag isminimized, and the vertical speed indicator is easyto interpret. Overcontrolling can be minimized byfirst neutralizing the controls and allowing the pitchattitude to stabilize; then readjusting the pitch atti-tude by noting the indications of the other pitchinstruments.

Occasionally, the vertical speed indicator may beslightly out of calibration. This could result in theinstrument indicating a slight climb or descent evenwhen the helicopter is in level flight. If it cannot bereadjusted properly, this error must be taken into con-sideration when using the vertical speed indicator forpitch control. For example, if the vertical speed indica-tor showed a descent of 100 f.p.m. when the helicopterwas in level flight, you would have to use that indica-tion as level flight. Any deviation from that readingwould indicate a change in attitude.

AIRSPEED INDICATORThe airspeed indicator gives an indirect indication ofhelicopter pitch attitude. With a given power settingand pitch attitude, the airspeed remains constant. If theairspeed increases, the nose is too low and should beraised. If the airspeed decreases, the nose is too highand should be lowered. A rapid change in airspeed indi-cates a large change in pitch attitude, and a slow changein airspeed indicates a small change in pitch attitude.There is very little lag in the indications of the airspeedindicator. If, while making attitude changes, you noticesome lag between control application and change ofairspeed, it is most likely due to cyclic control lag.Generally, a departure from the desired airspeed, due toan inadvertent pitch attitude change, also results in achange in altitude. For example, an increase in airspeeddue to a low pitch attitude results in a decrease in alti-tude. A correction in the pitch attitude regains both air-speed and altitude.

BANK CONTROLThe bank attitude of a helicopter is the angular relationof its lateral axis and the natural horizon. To maintain astraight course in visual flight, you must keep the lateral axis of the helicopter level with the natural hori-zon. Assuming the helicopter is in coordinated flight,any deviation from a laterally level attitude produces aturn. [Figure 12-13]

ATTITUDE INDICATORThe attitude indicator gives a direct indication of thebank attitude of the helicopter. For instrument flight,

BANK CONTRBANK CONTROLOLBANK CONTROL

Figure 12-13. The flight instruments used for bank control are the attitude, heading, and turn indicators.

12-10

the miniature aircraft and the horizon bar of the attitudeindicator are substituted for the actual helicopter andthe natural horizon. Any change in bank attitude of thehelicopter is indicated instantly by the miniature air-craft. For proper interpretations of this instrument, youshould imagine being in the miniature aircraft. If thehelicopter is properly trimmed and the rotor tilts, a turnbegins. The turn can be stopped by leveling the miniatureaircraft with the horizon bar. The ball in the turn-and-slipindicator should always be kept centered through properpedal trim.

The angle of bank is indicated by the pointer on thebanking scale at the top of the instrument. [Figure 12-14] Small bank angles, which may not be seen byobserving the miniature aircraft, can easily be deter-mined by referring to the banking scale pointer.

Pitch and bank attitudes can be determined simultane-ously on the attitude indicator. Even though the miniatureaircraft is not level with the horizon bar, pitch attitude canbe established by observing the relative position of theminiature aircraft and the horizon bar.

The attitude indicator may show small misrepresenta-tions of bank attitude during maneuvers that involveturns. This precession error can be immediatelydetected by closely cross-checking the other bankinstruments during these maneuvers. Precession nor-mally is noticed when rolling out of a turn. If, on thecompletion of a turn, the miniature aircraft is level and

the helicopter is still turning, make a small change ofbank attitude to center the turn needle and stop themovement of the heading indicator.

HEADING INDICATORIn coordinated flight, the heading indicator gives anindirect indication of the helicopter’s bank attitude.When a helicopter is banked, it turns. When the lateralaxis of the helicopter is level, it flies straight.Therefore, in coordinated flight, when the heading indi-cator shows a constant heading, the helicopter is levellaterally. A deviation from the desired heading indi-cates a bank in the direction the helicopter is turning.A small angle of bank is indicated by a slow change ofheading; a large angle of bank is indicated by a rapidchange of heading. If a turn is noticed, apply oppositecyclic until the heading indicator indicates the desiredheading, simultaneously checking that the ball is cen-tered. When making the correction to the desired head-ing, you should not use a bank angle greater than thatrequired to achieve a standard rate turn. In addition, ifthe number of degrees of change is small, limit thebank angle to the number of degrees to be turned. Bankangles greater than these require more skill and preci-sion in attaining the desired results. During straight-and-level flight, the heading indicator is the primaryreference for bank control.

TURN INDICATORDuring coordinated flight, the needle of the turn-and-slip indicator gives an indirect indication of the bankattitude of the helicopter. When the needle is dis-placed from the vertical position, the helicopter isturning in the direction of the displacement. Thus, ifthe needle is displaced to the left, the helicopter isturning left. Bringing the needle back to the verticalposition with the cyclic produces straight flight. Aclose observation of the needle is necessary to accu-rately interpret small deviations from the desiredposition.

Cross-check the ball of the turn-and-slip indicator todetermine that the helicopter is in coordinated flight. Ifthe rotor is laterally level and torque is properly com-pensated for by pedal pressure, the ball remains in thecenter. To center the ball, level the helicopter laterallyby reference to the other bank instruments, then centerthe ball with pedal trim. Torque correction pressuresvary as you make power changes. Always check theball following such changes.

COMMON ERRORS DURING STRAIGHT-AND-LEVEL FLIGHT1. Failure to maintain altitude.2. Failure to maintain heading.3. Overcontrolling pitch and bank during corrections.4. Failure to maintain proper pedal trim.5. Failure to cross-check all available instruments.

30°0°

60°

90°

Figure 12-14. The banking scale at the top of the attitude indi-cator indicates varying degrees of bank. In this example, thehelicopter is banked a little over 10° to the right.

12-11

POWER CONTROL DURING STRAIGHT-AND-LEVEL FLIGHTEstablishing specific power settings is accomplishedthrough collective pitch adjustments and throttle control, where necessary. For reciprocating poweredhelicopters, power indications are observed on the manifold pressure gauge. For turbine powered helicop-ters, power is observed on the torque gauge. (Since mostIFR certified helicopters are turbine powered, this discussion concentrates on this type of helicopter.)

At any given airspeed, a specific power setting deter-mines whether the helicopter is in level flight, in aclimb, or in a descent. For example, cruising airspeedmaintained with cruising power results in level flight.If you increase the power setting and hold the airspeedconstant, the helicopter climbs. Conversely, if youdecrease power and hold the airspeed constant, the heli-copter descends. As a rule of thumb, in a turbine-enginepowered helicopter, a 10 to 15 percent change in thetorque value required to maintain level flight results in aclimb or descent of approximately 500 f.p.m., if the air-speed remains the same.

If the altitude is held constant, power determines theairspeed. For example, at a constant altitude, cruisingpower results in cruising airspeed. Any deviation fromthe cruising power setting results in a change of air-speed. When power is added to increase airspeed, thenose of the helicopter pitches up and yaws to the rightin a helicopter with a counterclockwise main rotorblade rotation. When power is reduced to decrease air-speed, the nose pitches down and yaws to the left. Theyawing effect is most pronounced in single-rotor helicop-ters, and is absent in helicopters with counter-rotatingrotors. To counteract the yawing tendency of the helicop-ter, apply pedal trim during power changes.

To maintain a constant altitude and airspeed in levelflight, coordinate pitch attitude and power control. Therelationship between altitude and airspeed determinesthe need for a change in power and/or pitch attitude. Ifthe altitude is constant and the airspeed is high or low,change the power to obtain the desired airspeed.During the change in power, make an accurate inter-pretation of the altimeter; then counteract any devia-tion from the desired altitude by an appropriate changeof pitch attitude. If the altitude is low and the airspeedis high, or vice versa, a change in pitch attitude alonemay return the helicopter to the proper altitude and air-speed. If both airspeed and altitude are low, or if bothare high, a change in both power and pitch attitude isnecessary.

To make power control easy when changing airspeed, itis necessary to know the approximate power settings forthe various airspeeds that will be flown. When the air-

speed is to be changed any appreciable amount, adjustthe torque so that it is approximately five percent over orunder that setting necessary to maintain the new airspeed.As the power approaches the desired setting, include thetorque meter in the cross-check to determine when theproper adjustment has been accomplished. As the air-speed is changing, adjust the pitch attitude to maintain aconstant altitude. A constant heading should be main-tained throughout the change. As the desired airspeed isapproached, adjust power to the new cruising power set-ting and further adjust pitch attitude to maintain altitude.Overpowering and underpowering torque approximatelyfive percent results in a change of airspeed at a moderaterate, which allows ample time to adjust pitch and banksmoothly. The instrument indications for straight-and-level flight at normal cruise, and during the transitionfrom normal cruise to slow cruise are illustrated in fig-ures 12-15 and 12-16 on the next page. After the airspeedhas stabilized at slow cruise, the attitude indicator showsan approximate level pitch attitude.

The altimeter is the primary pitch instrument duringlevel flight, whether flying at a constant airspeed, orduring a change in airspeed. Altitude should not changeduring airspeed transitions. The heading indicatorremains the primary bank instrument. Whenever theairspeed is changed any appreciable amount, the torquemeter is momentarily the primary instrument for powercontrol. When the airspeed approaches that desired, theairspeed indicator again becomes the primary instru-ment for power control.

The cross-check of the pitch and bank instruments toproduce straight-and-level flight should be combinedwith the power control instruments. With a constantpower setting, a normal cross-check should be satisfactory. When changing power, the speed of thecross-check must be increased to cover the pitch andbank instruments adequately. This is necessary to counteract any deviations immediately.

COMMON ERRORS DURING AIRSPEED CHANGES1. Improper use of power.2. Overcontrolling pitch attitude.3. Failure to maintain heading.4. Failure to maintain altitude.5. Improper pedal trim.

STRAIGHT CLIMBS (CONSTANT AIRSPEEDAND CONSTANT RATE)For any power setting and load condition, there is onlyone airspeed that will give the most efficient rate ofclimb. To determine this, you should consult the climbdata for the type of helicopter being flown. The tech-nique varies according to the airspeed on entry andwhether you want to make a constant airspeed or con-stant rate climb.

12-12

ENTRYTo enter a constant airspeed climb from cruise airspeed,when the climb speed is lower than cruise speed, simul-taneously increase power to the climb power settingand adjust pitch attitude to the approximate climb atti-tude. The increase in power causes the helicopter tostart climbing and only very slight back cyclic pressureis needed to complete the change from level to climbattitude. The attitude indicator should be used to

accomplish the pitch change. If the transition fromlevel flight to a climb is smooth, the vertical speed indi-cator shows an immediate upward trend and then stopsat a rate appropriate to the stabilized airspeed and atti-tude. Primary and supporting instruments for climbentry are illustrated in figure 12-17.

When the helicopter stabilizes on a constant airspeedand attitude, the airspeed indicator becomes primary

Figure 12-16. Flight instrument indications in straight-and-level flight with airspeed decreasing.

Figure 12-15. Flight instrument indications in straight-and-level flight at normal cruise speed.

4050 60 70

8090

100

1101200

1020

30TORQUE

PERCENT

Supporting Pitch and Bank

Primary Power Primary Pitch

Supporting PitchPrimary BankSupporting Bank

Supporting Power

4050 60 70

8090

100

1101200

1020

30TORQUE

PERCENT

Primary Bank

Primary Power Initially

Primary PitchSupporting Pitch and Bank

Primary Power as Airspeed Approaches Desired Value

Supporting PitchSupporting Bank

12-13

for pitch. The torque meter continues to be primary forpower and should be monitored closely to determine ifthe proper climb power setting is being maintained.Primary and supporting instruments for a stabilizedconstant airspeed climb are shown in figure 12-18.

The technique and procedures for entering a constantrate climb are very similar to those previouslydescribed for a constant airspeed climb. For trainingpurposes, a constant rate climb is entered from climbairspeed. The rate used is the one that is appropriate for

4050 60 70

8090

100

1101200

1020

30TORQUE

PERCENT

Primary Pitch Supporting Bank

Primary Power

Supporting PitchPrimary BankSupporting Bank

Figure 12-17. Flight instrument indications during climb entry for a constant airspeed climb.

4050 60 70

8090

100

1101200

1020

30TORQUE

PERCENT

Primary Pitch Supporting Pitch and Bank

Primary Power

Supporting PitchPrimary BankSupporting Bank

Figure 12-18. Flight instrument indications in a stabilized, constant airspeed climb.

12-14

the particular helicopter being flown. Normally, in heli-copters with low climb rates, 500 f.p.m. is appropriate,in helicopters capable of high climb rates, use a rate of1,000 f.p.m.

To enter a constant rate climb, increase power to theapproximate setting for the desired rate. As power isapplied, the airspeed indicator is primary for pitch untilthe vertical speed approaches the desired rate. At thistime, the vertical speed indicator becomes primary forpitch. Change pitch attitude by reference to the attitudeindicator to maintain the desired vertical speed. Whenthe VSI becomes primary for pitch, the airspeed indica-tor becomes primary for power. Primary and supportinginstruments for a stabilized constant rate climb are illus-trated in figure 12-19. Adjust power to maintain desiredairspeed. Pitch attitude and power corrections should beclosely coordinated. To illustrate this, if the verticalspeed is correct but the airspeed is low, add power. Aspower is increased, it may be necessary to lower thepitch attitude slightly to avoid increasing the verticalrate. Adjust the pitch attitude smoothly to avoid over-controlling. Small power corrections usually will besufficient to bring the airspeed back to the desired indi-cation.

LEVELOFF The leveloff from a constant airspeed climb must bestarted before reaching the desired altitude. Although theamount of lead varies with the helicopter being flownand your piloting technique, the most important factor isvertical speed. As a rule of thumb, use 10 percent of thevertical velocity as your lead point. For example, if the

rate of climb is 500 f.p.m., initiate the leveloff approxi-mately 50 feet before the desired altitude. When theproper lead altitude is reached, the altimeter becomesprimary for pitch. Adjust the pitch attitude to the levelflight attitude for that airspeed. Cross-check the altime-ter and VSI to determine when level flight has beenattained at the desired altitude. To level off at cruise air-speed, if this speed is higher than climb airspeed, leavethe power at the climb power setting until the airspeedapproaches cruise airspeed, then reduce it to the cruisepower setting.

The leveloff from a constant rate climb is accomplishedin the same manner as the leveloff from a constant air-speed climb.

STRAIGHT DESCENTS (CONSTANTAIRSPEED AND CONSTANT RATE)A descent may be performed at any normal airspeed thehelicopter is capable of, but the airspeed must be deter-mined prior to entry. The technique is determined bywhether you want to perform a constant airspeed or aconstant rate descent.

ENTRYIf your airspeed is higher than descending airspeed, andyou wish to make a constant airspeed descent at thedescending airspeed, reduce power to the descendingpower setting and maintain a constant altitude usingcyclic pitch control. When you approach the descend-ing airspeed, the airspeed indicator becomes primaryfor pitch, and the torque meter is primary for power. Asyou hold the airspeed constant, the helicopter begins todescend. For a constant rate descent, reduce the power

4050 60 70

8090

100

1101200

1020

30TORQUE

PERCENT

Supporting Power

Supporting Pitch and Bank

Primary Bank

Primary Power

Primary PitchSupporting Bank

Figure 12-19. Flight instrument indications in a stabilized constant rate climb.

12-15

to the approximate setting for the desired rate. If thedescent is started at the descending airspeed, the air-speed indicator is primary for pitch until the VSIapproaches the desired rate. At this time, the verticalspeed indicator becomes primary for pitch, and the airspeed indicator becomes primary for power.Coordinate power and pitch attitude control as wasdescribed earlier for constant rate climbs.

LEVELOFFThe leveloff from a constant airspeed descent may bemade at descending airspeed or at cruise airspeed, ifthis is higher than descending airspeed. As in a climbleveloff, the amount of lead depends on the rate ofdescent and control technique. For a leveloff atdescending airspeed, the lead should be approximately10 percent of the vertical speed. At the lead altitude,simultaneously increase power to the setting necessaryto maintain descending airspeed in level flight. At thispoint, the altimeter becomes primary for pitch, and theairspeed indicator becomes primary for power.

To level off at a higher airspeed than descending air-speed, increase the power approximately 100 to 150 feetprior to reaching the desired altitude. The power settingshould be that which is necessary to maintain thedesired airspeed in level flight. Hold the vertical speedconstant until approximately 50 feet above the desiredaltitude. At this point, the altimeter becomes primaryfor pitch, and the airspeed indicator becomes primaryfor power. The leveloff from a constant rate descentshould be accomplished in the same manner as the lev-eloff from a constant airspeed descent.

COMMON ERRORS DURING STRAIGHT CLIMBSAND DESCENTS1. Failure to maintain heading.2. Improper use of power.3. Poor control of pitch attitude.4. Failure to maintain proper pedal trim.5. Failure to level off on desired altitude.

TURNSWhen making turns by reference to the flight instru-ments, they should be made at a definite rate. Turnsdescribed in this chapter are those that do not exceed astandard rate of 3° per second as indicated on the turn-and-slip indicator. True airspeed determines the angleof bank necessary to maintain a standard rate turn. Arule of thumb to determine the approximate angle ofbank required for a standard rate turn is to divide yourairspeed by 10 and add one-half the result. For exam-ple, at 60 knots, approximately 9° of bank is required(60 ÷ 10 = 6 + 3 = 9); at 80 knots, approximately 12° ofbank is needed for a standard rate turn.

To enter a turn, apply lateral cyclic in the direction of thedesired turn. The entry should be accomplishedsmoothly, using the attitude indicator to establish theapproximate bank angle. When the turn indicator indi-cates a standard rate turn, it becomes primary for bank.The attitude indicator now becomes a supporting instru-ment. During level turns, the altimeter is primary forpitch, and the airspeed indicator is primary for power.Primary and supporting instruments for a stabilized stan-dard rate turn are illustrated in figure 12-20. If an

Figure 12-20. Flight instrument indications for a standard rate turn to the left.

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Primary Bank Initially Supporting Pitch

Primary Power Primary Pitch

Supporting PitchPrimary Bank as Turn is Established

Supporting Power

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increase in power is required to maintain airspeed, slightforward cyclic pressure may be required since the heli-copter tends to pitch up as collective pitch angle isincreased. Apply pedal trim, as required, to keep the ballcentered.

To recover to straight-and-level flight, apply cyclic inthe direction opposite the turn. The rate of roll-outshould be the same as the rate used when rolling intothe turn. As you initiate the turn recover, the attitudeindicator becomes primary for bank. When the helicop-ter is approximately level, the heading indicatorbecomes primary for bank as in straight-and-levelflight. Cross-check the airspeed indicator and ballclosely to maintain the desired airspeed and pedal trim.

TURNS TO A PREDETERMINED HEADINGA helicopter turns as long as its lateral axis is tilted; there-fore, the recovery must start before the desired heading isreached. The amount of lead varies with the rate of turnand your piloting technique.

As a guide, when making a 3° per second rate of turn,use a lead of one-half the bank angle. For example, ifyou are using a 12° bank angle, use half of that, or 6°,as the lead point prior to your desired heading. Use thislead until you are able to determine the exact amountrequired by your particular technique. The bank angleshould never exceed the number of degrees to beturned. As in any standard rate turn, the rate of recov-ery should be the same as the rate for entry. Duringturns to predetermined headings, cross-check the pri-mary and supporting pitch, bank, and power instru-ments closely.

TIMED TURNSA timed turn is a turn in which the clock and turn-and-slip indicator are used to change heading a definitenumber of degrees in a given time. For example, usinga standard rate turn, a helicopter turns 45° in 15 sec-onds. Using a half-standard rate turn, the helicopterturns 45° in 30 seconds. Timed turns can be used ifyour heading indicator becomes inoperative.

Prior to performing timed turns, the turn coordinatorshould be calibrated to determine the accuracy of itsindications. To do this, establish a standard rate turn byreferring to the turn-and-slip indicator. Then as thesweep second hand of the clock passes a cardinal point(12, 3, 6, or 9), check the heading on the heading indi-cator. While holding the indicated rate of turn constant,note the heading changes at 10-second intervals. If thehelicopter turns more or less than 30° in that interval, asmaller or larger deflection of the needle is necessaryto produce a standard rate turn. When you have cali-brated the turn-and-slip indicator during turns in eachdirection, note the corrected deflections, if any, andapply them during all timed turns.

You use the same cross-check and control technique inmaking timed turns that you use to make turns to a pre-determined heading, except that you substitute theclock for the heading indicator. The needle of the turn-and-slip indicator is primary for bank control, thealtimeter is primary for pitch control, and the airspeedindicator is primary for power control. Begin the roll-inwhen the clock’s second hand passes a cardinal point,hold the turn at the calibrated standard-rate indication,or half-standard-rate for small changes in heading, andbegin the roll-out when the computed number of sec-onds has elapsed. If the roll-in and roll-out rates are thesame, the time taken during entry and recovery neednot be considered in the time computation.

If you practice timed turns with a full instrument panel,check the heading indicator for the accuracy of yourturns. If you execute the turns without the heading indi-cator, use the magnetic compass at the completion ofthe turn to check turn accuracy, taking compass devia-tion errors into consideration.

CHANGE OF AIRSPEED IN TURNSChanging airspeed in turns is an effective maneuver forincreasing your proficiency in all three basic instru-ment skills. Since the maneuver involves simultaneouschanges in all components of control, proper executionrequires a rapid cross-check and interpretation, as wellas smooth control. Proficiency in the maneuver alsocontributes to your confidence in the instruments dur-ing attitude and power changes involved in more com-plex maneuvers.

Pitch and power control techniques are the same asthose used during airspeed changes in straight-and-level flight. As discussed previously, the angle of banknecessary for a given rate of turn is proportional to thetrue airspeed. Since the turns are executed at standardrate, the angle of bank must be varied in direct pro-portion to the airspeed change in order to maintain aconstant rate of turn. During a reduction of airspeed,you must decrease the angle of bank and increase thepitch attitude to maintain altitude and a standard rateturn.

The altimeter and the needle on the turn indicatorshould remain constant throughout the turn. Thealtimeter is primary for pitch control, and the turn nee-dle is primary for bank control. The torque meter isprimary for power control while the airspeed is chang-ing. As the airspeed approaches the new indication, theairspeed indicator becomes primary for power control.

Two methods of changing airspeed in turns may beused. In the first method, airspeed is changed after theturn is established. In the second method, the airspeedchange is initiated simultaneously with the turn entry.The first method is easier, but regardless of the method

12-17

used, the rate of cross-check must be increased as youreduce power. As the helicopter decelerates, check thealtimeter and VSI for needed pitch changes, and thebank instruments for needed bank changes. If the needleof the turn-and-slip indicator shows a deviation fromthe desired deflection, change the bank. Adjust pitchattitude to maintain altitude. When the airspeedapproaches that desired, the airspeed indicator becomesprimary for power control. Adjust the torque meter tomaintain the desired airspeed. Use pedal trim to ensurethe maneuver is coordinated.

Until your control technique is very smooth, frequentlycross-check the attitude indicator to keep from over-controlling and to provide approximate bank anglesappropriate for the changing airspeeds.

30° BANK TURNA turn using 30° of bank is seldom necessary, or advis-able, in IMC, but it is an excellent maneuver to increaseyour ability to react quickly and smoothly to rapidchanges of attitude. Even though the entry and recov-ery technique are the same as for any other turn, youwill probably find it more difficult to control pitchbecause of the decrease in vertical lift as the bankincreases. Also, because of the decrease in vertical lift,there is a tendency to lose altitude and/or airspeed.Therefore, to maintain a constant altitude and airspeed,additional power is required. You should not initiate acorrection, however, until the instruments indicate theneed for a correction. During the maneuver, note theneed for a correction on the altimeter and vertical speedindicator, then check the indications on the attitude

indicator, and make the necessary adjustments. Afteryou have made this change, again check the altimeterand vertical speed indicator to determine whether ornot the correction was adequate.

CLIMBING AND DESCENDING TURNSFor climbing and descending turns, the techniquesdescribed earlier for straight climbs and descents andthose for standard rate turns are combined. For practice,start the climb or descent and turn simultaneously. Theprimary and supporting instruments for a stabilized con-stant airspeed left climbing turn are illustrated in figure12-21. The leveloff from a climbing or descending turnis the same as the leveloff from a straight climb ordescent. To recover to straight-and-level flight, you maystop the turn and then level off, level off and then stopthe turn, or simultaneously level off and stop the turn.During climbing and descending turns, keep the ball ofthe turn indicator centered with pedal trim.

COMPASS TURNSThe use of gyroscopic heading indicators make head-ing control very easy. However, if the heading indica-tor fails or your helicopter does not have one installed,you must use the magnetic compass for heading refer-ence. When making compass-only turns, you need toadjust for the lead or lag created by acceleration anddeceleration errors so that you roll out on the desiredheading. When turning to a heading of north, the leadfor the roll-out must include the number of degrees ofyour latitude plus the lead you normally use in recov-ery from turns. During a turn to a south heading, main-tain the turn until the compass passes south the number

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Primary Power

Supporting Pitch and Bank

Primary Bank

Primary Pitch

Supporting Pitch

Figure 12-21. Flight instrument indications for a stabilized left climbing turn at a constant airspeed.

12-18

COMMON ERRORS DURINGUNUSUAL ATTITUDE RECOVERIES1. Failure to make proper pitch correction.2. Failure to make proper bank correction.3. Failure to make proper power correction.4. Overcontrol of pitch and/or bank attitude.5. Overcontrol of power.6. Excessive loss of altitude.

EMERGENCIESEmergencies under instrument flight are handled simi-larly to those occurring during VFR flight. A thoroughknowledge of the helicopter and its systems, as well asgood aeronautical knowledge and judgment, preparesyou to better handle emergency situations. Safe opera-tions begin with preflight planning and a thorough pre-flight. Plan your route of flight so that there are adequatelanding sites in the event you have to make an emer-gency landing. Make sure you have all your resources,such as maps, publications, flashlights, and fire extin-guishers readily available for use in an emergency.

During any emergency, you should first fly the aircraft.This means that you should make sure the helicopter isunder control, including the determination of emergencylanding sites. Then perform the emergency checklistmemory items, followed by written items in the RFM.Once all these items are under control, you should notifyATC. Declare any emergency on the last assigned ATCfrequency, or if one was not issued, transmit on the emer-gency frequency 121.5. Set the transponder to the emer-gency squawk code 7700. This code triggers an alarm ora special indicator in radar facilities.

Most in-flight emergencies, including low fuel and acomplete electrical failure, require you to land as soonas possible. In the event of an electrical fire, turn all non-essential equipment off and land immediately. Someessential electrical instruments, such as the attitude indi-cator, may be required for a safe landing. A navigationradio failure may not require an immediate landing aslong as the flight can continue safely. In this case, youshould land as soon as practical. ATC may be able toprovide vectors to a safe landing area. For the specificdetails on what to do during an emergency, you shouldrefer to the RFM for the helicopter you are flying.

of degrees of your latitude, minus your normal roll-outlead. For example, when turning from an easterlydirection to north, where the latitude is 30°, start theroll-out when the compass reads 037° (30° plus one-half the 15° angle of bank, or whatever amount isappropriate for your rate of roll-out). When turningfrom an easterly direction to south, start the roll-outwhen the magnetic compass reads 203° (180° plus 30°minus one-half the angle of bank). When making sim-ilar turns from a westerly direction, the appropriatepoints at which to begin your roll-out would be 323°for a turn to north, and 157° for a turn to south.

COMMON ERRORS DURING TURNS1. Failure to maintain desired turn rate.2. Failure to maintain altitude in level turns.3. Failure to maintain desired airspeed.4. Variation in the rate of entry and recovery.5. Failure to use proper lead in turns to a heading.6. Failure to properly compute time during timed turns.7. Failure to use proper leads and lags during the

compass turns.8. Improper use of power.9. Failure to use proper pedal trim.

UNUSUAL ATTITUDESAny maneuver not required for normal helicopter instru-ment flight is an unusual attitude and may be caused byany one or a combination of factors, such as turbulence,disorientation, instrument failure, confusion, preoccupa-tion with cockpit duties, carelessness in cross-checking,errors in instrument interpretation, or lack of proficiencyin aircraft control. Due to the instability characteristicsof the helicopter, unusual attitudes can be extremely crit-ical. As soon as you detect an unusual attitude, make arecovery to straight-and-level flight as soon as possiblewith a minimum loss of altitude.

To recover from an unusual attitude, correct bank andpitch attitude, and adjust power as necessary. All com-ponents are changed almost simultaneously, with littlelead of one over the other. You must be able to performthis task with and without the attitude indicator. If thehelicopter is in a climbing or descending turn, correctbank, pitch, and power. The bank attitude should becorrected by referring to the turn-and-slip indicator andattitude indicator. Pitch attitude should be corrected byreference to the altimeter, airspeed indicator, VSI, andattitude indicator. Adjust power by referring to the air-speed indicator and torque meter.

Since the displacement of the controls used in recover-ies from unusual attitudes may be greater than those fornormal flight, take care in making adjustments asstraight-and-level flight is approached. Cross-check theother instruments closely to avoid overcontrolling.

Land as soon as possible—Land without delay at the nearest suitablearea, such as an open field, at which a safe approach and landing isassured.

Land immediately—The urgency of the landing is paramount. The pri-mary consideration is to assure the survival of the occupants. Landing intrees, water, or other unsafe areas should be considered only as a lastresort.

Land as soon as practical—The landing site and duration of flight areat the discretion of the pilot. Extended flight beyond the nearestapproved landing area is not recommended.

12-19

AUTOROTATIONSBoth straight-ahead and turning autorotations shouldbe practiced by reference to instruments. This trainingwill ensure that you can take prompt corrective actionto maintain positive aircraft control in the event of anengine failure.

To enter autorotation, reduce collective pitch smoothlyto maintain a safe rotor r.p.m. and apply pedal trim tokeep the ball of the turn-and-slip indicator centered.The pitch attitude of the helicopter should be approxi-mately level as shown by the attitude indicator. The airspeed indicator is the primary pitch instrument andshould be adjusted to the recommended autorotationspeed. The heading indicator is primary for bank in astraight-ahead autorotation. In a turning autorotation, astandard rate turn should be maintained by reference tothe needle of the turn-and-slip indicator.

COMMON ERRORS DURING AUTOROTATIONS1. Uncoordinated entry due to improper pedal trim.2. Poor airspeed control due to improper pitch attitude.3. Poor heading control in straight-ahead autorotations.4. Failure to maintain proper rotor r.p.m.5. Failure to maintain a standard rate turn during turn-

ing autorotations.

SERVO FAILUREMost helicopters certified for single-pilot IFR flight arerequired to have autopilots, which greatly reduces pilotworkload. If an autopilot servo fails, however, youhave to resume manual control of the helicopter. Howmuch your workload increases, depends on whichservo fails. If a cyclic servo fails, you may want to landimmediately as the workload increases tremendously.

If an antitorque or collective servo fails, you might beable to continue to the next suitable landing site.

INSTRUMENT TAKEOFFThis maneuver should only be performed as part ofyour training for an instrument rating. The proceduresand techniques described here should be modified, asnecessary, to conform with those set forth in the operat-ing instructions for the particular helicopter beingflown.

Adjust the miniature aircraft in the attitude indicator,as appropriate, for the aircraft being flown. After thehelicopter is aligned with the runway or takeoff pad, toprevent forward movement of a helicopter equippedwith a wheel-type landing gear, set the parking brakeor apply the toe brakes. If the parking brake is used, itmust be unlocked after the takeoff has been completed.Apply sufficient friction to the collective pitch control tominimize overcontrolling and to prevent creeping.Excessive friction should be avoided since this limitscollective pitch movement.

After checking all instruments for proper indications,start the takeoff by applying collective pitch and a prede-termined power setting. Add power smoothly andsteadily to gain airspeed and altitude simultaneously andto prevent settling to the ground. As power is applied andthe helicopter becomes airborne, use the antitorque ped-als initially to maintain the desired heading. At the sametime, apply forward cyclic to begin accelerating toclimbing airspeed. During the initial acceleration, thepitch attitude of the helicopter, as read on the attitudeindicator, should be one to two bar widths low. The pri-mary and supporting instruments after becoming airborneare illustrated in figure 12-22. As the airspeed increases

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Primary Power

Primary Pitch Supporting Bank

Supporting Pitch

Supporting Bank

Supporting Pitch

Supporting PitchPrimary Bank

Figure 12-22. Flight instrument indications during an instrument takeoff.

12-20

to the appropriate climb airspeed, adjust pitch graduallyto climb attitude. As climb airspeed is reached, reducepower to the climb power setting and transition to a fullycoordinated straight climb.

During the initial climbout, minor heading correc-tions should be made with pedals only until suffi-cient airspeed is attained to transition to fullycoordinated flight. Throughout the instrument take-off, instrument cross-check and interpretations must

be rapid and accurate, and aircraft control positiveand smooth.

COMMON ERRORS DURING INSTRUMENTTAKEOFFS1. Failure to maintain heading.2. Overcontrolling pedals.3. Failure to use required power.4. Failure to adjust pitch attitude as climbing air-

speed is reached.

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Flying at night can be a very pleasant experience. Theair is generally cooler and smoother, resulting in betterhelicopter performance and a more comfortable flight.You generally also experience less traffic and less radiocongestion.

NIGHT FLIGHT PHYSIOLOGYBefore discussing night operations, it is important youunderstand how your vision is affected at night andhow to counteract the visual illusions, which you mightencounter.

VISION IN FLIGHTVision is by far the most important sense that youhave, and flying is obviously impossible without it.Most of the things you perceive while flying arevisual or heavily supplemented by vision. The visualsense is especially important in collision avoidanceand depth perception. Your vision sensors are youreyes, even though they are not perfect in the way theyfunction or see objects. Since your eyes are notalways able to see all things at all times, illusions andblindspots occur. The more you understand the eyeand how it functions, the easier it is to compensate forthese illusions and blindspots.

THE EYEThe eye works in much the same way as a camera. Bothhave an aperture, lens, method of focusing, and a sur-face for registering images. [Figure 13-1].

Vision is primarily the result of light striking a photo-sensitive layer, called the retina, at the back of the eye.The retina is composed of light-sensitive cones androds. The cones in your eye perceive an image bestwhen the light is bright, while the rods work best in lowlight. The pattern of light that strikes the cones and rodsis transmitted as electrical impulses by the optic nerveto the brain where these signals are interpreted as animage. The area where the optic nerve meets the retinacontains no cones or rods, creating a blind spot invision. Normally, each eye compensates for the other’sblind spot. [Figure 13-2]

CONESCones are concentrated around the center of theretina. They gradually diminish in number as the dis-tance from the center increases. Cones allow you toperceive color by sensing red, blue, and green light.

Directly behind the lens, on the retina, is a small,notched area called the fovea. This area contains onlya high concentration of cone receptors. When youlook directly at an object, the image is focusedmainly on the fovea. The cones, however, do not

The rods and cones (film) of the retina are the receptors, which record the image and transmit it through the optic nerve to the brain for interpretation.

Light passes through the cornea

(the transparent window on the front of the eye) and then through the lens to focus on the retina.

The pupil (aperture) is the opening at the center of

the iris. The size of the pupil is adjusted to

control the amount of light entering the eye.

LensIris

Pupil

Cornea

Optic Nerve Retina

Rods and Cones

Fovea (All Cones)

Rod Concentration

{

{

{

{

{

Figure 13-1. A camera is able to focus on near and far objectsby changing the distance between the lens and the film. Youcan see objects clearly at various distances because theshape of your eye’s lens is changed automatically by smallmuscles.

Figure 13-2. This illustration provides a dramatic example ofthe eye’s blind spot. Cover your right eye and hold this pageat arm’s length. Focus your left eye on the X in the right sideof the visual, and notice what happens to the aircraft as youslowly bring the page closer to your eye.

13-2

function well in darkness, which explains why youcannot see color as vividly at night as you can duringthe day. [Figure 13-3]

RODSThe rods are our dim light and night receptors and areconcentrated outside the fovea area. The number ofrods increases as the distance from the fovea increases.Rods sense images only in black and white. Becausethe rods are not located directly behind the pupil, theyare responsible for much of our peripheral vision.Images that move are perceived more easily by the rodareas than by the cones in the fovea. If you have everseen something move out of the corner of your eye, itwas most likely detected by your rod receptors.

Since the cones do not function well in the dark, youmay not be able to see an object if you look directly atit. The concentration of cones in the fovea can make anight blindspot at the center of your vision. To see anobject clearly, you must expose the rods to the image.This is accomplished by looking 5° to 10° off center ofthe object you want to see. You can try out this effecton a dim light in a darkened room. When you lookdirectly at the light, it dims or disappears altogether. Ifyou look slightly off center, it becomes clearer andbrighter. [Figure 13-4]

How well you see at night is determined by the rods inyour eyes, as well as the amount of light allowed intoyour eyes. The wider the pupil is open at night, the bet-ter your night vision becomes.

NIGHT VISIONThe cones in your eyes adapt quite rapidly to changes inlight intensities, but the rods do not. If you have everwalked from bright sunlight into a dark movie theater, youhave experienced this dark adaptation period. The rodscan take approximately 30 minutes to fully adapt to thedark. Abright light, however, can completely destroy yournight adaptation and severely restrict your visual acuity.

There are several things you can do to keep your eyesadapted to the dark. The first is obvious; avoid brightlights before and during the flight. For 30 minutesbefore a night flight, avoid any bright light sources,such as headlights, landing lights, strobe lights, orflashlights. If you encounter a bright light, close oneeye to keep it light sensitive. This allows you to seeagain once the light is gone. Light sensitivity also canbe gained by using sunglasses if you will be flying fromdaylight into an area of increasing darkness.

Red cockpit lighting also helps preserve your nightvision, but red light severely distorts some colors, andcompletely washes out the color red. This makes read-ing an aeronautical chart difficult. A dim white light orcarefully directed flashlight can enhance your nightreading ability. While flying at night, keep the instru-ment panel and interior lights turned up no higher thannecessary. This helps you see outside visual referencesmore easily. If your eyes become blurry, blinking morefrequently often helps.

Your diet and general physical health have an impacton how well you can see in the dark. Deficiencies invitamins A and C have been shown to reduce night acu-ity. Other factors, such as carbon monoxide poisoning,smoking, alcohol, certain drugs, and a lack of oxygenalso can greatly decrease your night vision.

NIGHT SCANNINGGood night visual acuity is needed for collision avoid-ance. Night scanning, like day scanning, uses a seriesof short, regularly spaced eye movements in 10° sec-tors. Unlike day scanning, however, off-center viewingis used to focus objects on the rods rather than the foveablindspot. When you look at an object, avoid staring atit too long. If you stare at an object without movingyour eyes, the retina becomes accustomed to the lightintensity and the image begins to fade. To keep itclearly visible, new areas in the retina must be exposedto the image. Small, circular eye movements helpeliminate the fading. You also need to move your eyesmore slowly from sector to sector than during the dayto prevent blurring.

Focus on Fovea

Cones Active

Night Blindspot

Rods Active

Figure 13-3. The best vision in daylight is obtained by look-ing directly at the object. This focuses the image on thefovea, where detail is best seen.

Figure 13-4. In low light, the cones lose much of their visualacuity, while rods become more receptive. The eye sacrificessharpness for sensitivity. Your ability to see an object directlyin front of you is reduced, and you lose much of your depthperception, as well as your judgment of size.

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AIRCRAFT LIGHTINGIn order to see other aircraft more clearly, regulationsrequire that all aircraft operating during the night hourshave special lights and equipment. The requirementsfor operating at night are found in Title 14 of the Codeof Federal Regulations (14 CFR) part 91. In addition toaircraft lighting, the regulations also provide a defini-tion of nighttime, currency requirements, fuel reserves,and necessary electrical systems.

Position lights enable you to locate another aircraft, aswell as help you determine its direction of flight. Theapproved aircraft lights for night operations are a greenlight on the right cabin side or wingtip, a red light onthe left cabin side or wingtip, and a white position lighton the tail. In addition, flashing aviation red or whiteanticollision lights are required for night flights. Theseflashing lights can be in a number of locations, but aremost commonly found on the top and bottom of thecabin. [Figure 13-5]

VISUAL ILLUSIONSThere are many different types of visual illusions thatyou can experience at any time, day or night. The nextfew paragraphs cover some of the illusions that com-monly occur at night.

AUTOKINESISAutokinesis is caused by staring at a single point oflight against a dark background, such as a ground lightor bright star, for more than a few seconds. After a fewmoments, the light appears to move on its own. To pre-vent this illusion, you should focus your eyes onobjects at varying distances and not fixate on one tar-get, as well as maintain a normal scan pattern.

NIGHT MYOPIAAnother problem associated with night flying is nightmyopia, or night-induced nearsightedness. With noth-ing to focus on, your eyes automatically focus on apoint just slightly ahead of your aircraft. Searching outand focusing on distant light sources, no matter howdim, helps prevent the onset of night myopia.

FALSE HORIZONA false horizon can occur when the natural horizon isobscured or not readily apparent. It can be generated byconfusing bright stars and city lights. [Figure 13-6] Itcan also occur while you are flying toward the shore ofan ocean or a large lake. Because of the relative darknessof the water, the lights along the shoreline can be mis-taken for the stars in the sky. [Figure 13-7]

WhiteRed

Green

Your Helicopter

White

Green

Red

Red Green

White

Figure 13-5. By interpreting the position lights on other aircraft, you can determine whether the aircraft is flying away from youor is on a collision course. If you see a red position light to the right of a green light, such as shown by aircraft number 1, it isflying toward you. You should watch this aircraft closely and be ready to change course. Aircraft number 2, on the other hand,is flying away from you, as indicated by the white position light.

Apparent Horizon

Actual H

orizon

Apparent Horizon

Actual Horizon

Figure 13-6. You can place your helicopter in an extremelydangerous flight attitude if you align the helicopter with thewrong lights. Here, the helicopter is aligned with a road andnot the horizon.

Figure 13-7. In this illusion, the shoreline is mistaken for thehorizon. In an attempt to correct for the apparent nose-highattitude, a pilot may lower the collective and attempt to fly“beneath the shore.”

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LANDING ILLUSIONSLanding illusions occur in many forms. Above feature-less terrain at night, there is a natural tendency to fly alower-than-normal approach. Elements that cause anytype of visual obscuration, such as rain, haze, or a darkrunway environment also can cause low approaches.Bright lights, steep surrounding terrain, and a wide run-way can produce the illusion of being too low, with atendency to fly a higher-than-normal approach.

NIGHT FLIGHTThe night flying environment and the techniques you usewhen flying at night, depend on outside conditions.Flying on a bright, clear, moonlit evening when the visi-bility is good and the wind is calm, is not much differentfrom flying during the day. However, if you are flyingon an overcast night over a sparsely populated area,with little or no outside lights from the ground, the sit-uation is quite different. Visibility is restricted so youhave to be more alert in steering clear of obstructionsand low clouds. Your options are also limited in theevent of an emergency, as it is more difficult to finda place to land and determine wind direction andspeed. At night, you have to rely more heavily on theaircraft systems, such as lights, flight instruments, andnavigation equipment. As a precaution, if the visibilityis limited or outside references are inadequate, youshould strongly consider delaying the flight until con-ditions improve, unless you have received training ininstrument flight and your helicopter has the appropri-ate instrumentation and equipment.

PREFLIGHTThe preflight inspection is performed in the usual man-ner, except it should be done in a well lit area or with aflashlight. Careful attention must be paid to the aircraftelectrical system. In helicopters equipped with fuses, aspare set is required by regulation, and common sense,so make sure they are onboard. If the helicopter isequipped with circuit breakers, check to see that theyare not tripped. A tripped circuit breaker may be anindication of an equipment malfunction. Reset it andcheck the associated equipment for proper operation.

Check all the interior lights, especially the instrumentand panel lights. The panel lighting can usually be con-trolled with a rheostat or dimmer switch, allowing youto adjust the intensity. If the lights are too bright, a glaremay reflect off the windshield creating a distraction.Always carry a flashlight with fresh batteries to pro-vide an alternate source of light if the interior lightsmalfunction.

All aircraft operating between sunset and sunrise arerequired to have operable navigation lights. Turnthese lights on during the preflight to inspect them

visually for proper operation. Between sunset andsunrise, theses lights must be on any time the engineis running.

All recently manufactured aircraft certified for nightflight, must have an anticollision light that makes theaircraft more visible to other pilots. This light is eithera red or white flashing light and may be in the form ofa rotating beacon or a strobe. While anticollision lightsare required for night VFR flights, they may be turnedoff any time they create a distraction for the pilot.

One of the first steps in preparation for night flight isbecoming thoroughly familiar with the helicopter’scockpit, instrumentation and control layout. It is rec-ommended that you practice locating each instrument,control, and switch, both with and without cabin lights.Since the markings on some switches and circuitbreaker panels may be hard to read at night, you shouldassure yourself that you are able to locate and use thesedevices, and read the markings in poor light conditions.Before you start the engine, make sure all necessaryequipment and supplies needed for the flight, such ascharts, notepads, and flashlights, are accessible andready for use.

ENGINE STARTING AND ROTORENGAGEMENTUse extra caution when starting the engine and engag-ing the rotors, especially in dark areas with little or nooutside lights. In addition to the usual call of “clear,”turn on the position and anticollision lights. If condi-tions permit, you might also want to turn the landinglight on momentarily to help warn others that you areabout to start the engine and engage the rotors.

TAXI TECHNIQUELanding lights usually cast a beam that is narrow andconcentrated ahead of the helicopter, so illumination tothe side is minimal. Therefore, you should slow yourtaxi at night, especially in congested ramp and parkingareas. Some helicopters have a hover light in additionto a landing light, which illuminates a larger area underthe helicopter.

When operating at an unfamiliar airport at night, youshould ask for instructions or advice concerning localconditions, so as to avoid taxiing into areas of con-struction, or unlighted, unmarked obstructions. Groundcontrollers or UNICOM operators are usually coopera-tive in furnishing you with this type of information.

TAKEOFFBefore takeoff, make sure that you have a clear, unob-structed takeoff path. At airports, you may accomplishthis by taking off over a runway or taxiway, however, if

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you are operating off-airport, you must pay more atten-tion to the surroundings. Obstructions may also be dif-ficult to see if you are taking off from an unlighted area.Once you have chosen a suitable takeoff path, select apoint down the takeoff path to use for directional refer-ence. During a night takeoff, you may notice a lack ofreliable outside visual references after you are airborne.This is particularly true at small airports and off-airportlanding sites located in sparsely populated areas. Tocompensate for the lack of outside references, use theavailable flight instruments as an aid. Check the altime-ter and the airspeed indicator to verify the proper climbattitude. An attitude indicator, if installed, can enhanceyour attitude reference.

The first 500 feet of altitude after takeoff is consideredto be the most critical period in transitioning from thecomparatively well-lighted airport or heliport intowhat sometimes appears to be total darkness. A takeoffat night is usually an “altitude over airspeed” maneu-ver, meaning you will most likely perform a nearlymaximum performance takeoff. This improves thechances for obstacle clearance and enhances safety.When performing this maneuver, be sure to avoid thecross-hatched or shaded areas of the height-velocitydiagram.

EN ROUTE PROCEDURESIn order to provide a higher margin of safety, it is rec-ommended that you select a cruising altitude somewhathigher than normal. There are several reasons for this.First, a higher altitude gives you more clearancebetween obstacles, especially those that are difficult tosee at night, such as high tension wires and unlightedtowers. Secondly, in the event of an engine failure, youhave more time to set up for a landing and the glidingdistance is greater giving you more options in making asafe landing. Thirdly, radio reception is improved, par-ticularly if you are using radio aids for navigation.

During your preflight planning, it is recommended thatyou select a route of flight that keeps you within reachof an airport, or any safe landing site, as much of thetime as possible. It is also recommended that you fly asclose as possible to a populated or lighted area such asa highway or town. Not only does this offer moreoptions in the event of an emergency, but also makesnavigation a lot easier. A course comprised of a seriesof slight zig-zags to stay close to suitable landing sitesand well lighted areas, only adds a little more time anddistance to an otherwise straight course.

In the event that you have to make a forced landing atnight, use the same procedure recommended for day-

time emergency landings. If available, turn on the land-ing light during the final descent to help in avoidingobstacles along your approach path.

COLLISION AVOIDANCE AT NIGHTAt night, the outside visual references are greatlyreduced especially when flying over a sparsely popu-lated area with little or no lights. The result is that youtend to focus on a single point or instrument, makingyou less aware of the other traffic around. You mustmake a special effort to devote enough time to scan fortraffic. You can determine another aircraft’s directionof flight by interpreting the position and anticollisionlights.

APPROACH AND LANDINGNight approaches and landings do have some advan-tages over daytime approaches, as the air is generallysmoother and the disruptive effects of turbulence andexcessive crosswinds are often absent. However, thereare a few special considerations and techniques thatapply to approaches at night. For example, when land-ing at night, especially at an unfamiliar airport, makethe approach to a lighted runway and then use the taxi-ways to avoid unlighted obstructions or equipment.

Carefully controlled studies have revealed that pilotshave a tendency to make lower approaches at nightthan during the day. This is potentially dangerous asyou have a greater chance of hitting an obstacle, suchas an overhead wire or fence, which are difficult to see.It is good practice to make steeper approaches at night,thus increasing any obstacle clearance. Monitor youraltitude and rate of descent using the altimeter.

Another tendency is to focus too much on the landingarea and not pay enough attention to airspeed. If toomuch airspeed is lost, a settling-with-power conditionmay result. Maintain the proper attitude during theapproach, and make sure you keep some forward air-speed and movement until close to the ground. Outsidevisual reference for airspeed and rate of closure maynot be available, especially when landing in anunlighted area, so pay special attention to the airspeedindicator

Although the landing light is a helpful aid when mak-ing night approaches, there is an inherent disadvantage.The portion of the landing area illuminated by the land-ing light seems higher than the dark area surroundingit. This effect can cause you to terminate the approachat too high an altitude, resulting in a settling-with-power condition and a hard landing.

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Aeronautical decision making (ADM) is a systematicapproach to the mental process used by pilots to con-sistently determine the best course of action in responseto a given set of circumstances. The importance oflearning effective ADM skills cannot be overempha-sized. While progress is continually being made in theadvancement of pilot training methods, aircraft equip-ment and systems, and services for pilots, accidentsstill occur. Despite all the changes in technology toimprove flight safety, one factor remains the same—the human factor. It is estimated that approxi-mately 65 percent of the total rotorcraft accidents arehuman factors related.

Historically, the term “pilot error” has been used todescribe the causes of these accidents. Pilot errormeans that an action or decision made by the pilot wasthe cause of, or a contributing factor that lead to, theaccident. This definition also includes the pilot’s fail-ure to make a decision or take action. From a broaderperspective, the phrase “human factors related” moreaptly describes these accidents since it is usually not asingle decision that leads to an accident, but a chain ofevents triggered by a number of factors.

The poor judgment chain, sometimes referred to as the“error chain,” is a term used to describe this concept ofcontributing factors in a human factors related acci-dent. Breaking one link in the chain normally is all thatis necessary to change the outcome of the sequence ofevents. The following is an example of the type of sce-nario illustrating the poor judgment chain.

A helicopter pilot, with limited experience flying inadverse weather, wants to be back at his home airportin time to attend an important social affair. He isalready 30 minutes late. Therefore, he decides not torefuel his helicopter, since he should get back homewith at least 20 minutes of reserve. In addition, in spiteof his inexperience, he decides to fly through an area ofpossible thunderstorms in order to get back just beforedark. Arriving in the thunderstorm area, he encounterslightning, turbulence, and heavy clouds. Night isapproaching, and the thick cloud cover makes it verydark. With his limited fuel supply, he is not able to cir-cumnavigate the thunderstorms. In the darkness andturbulence, the pilot becomes spatially disorientedwhile attempting to continue flying with visual refer-ence to the ground instead of using what instrumentshe has to make a 180° turn. In the ensuing crash, thepilot is seriously injured and the helicopter completelydestroyed.

By discussing the events that led to this accident, wecan understand how a series of judgmental errors contributed to the final outcome of this flight. Forexample, one of the first elements that affected thepilot’s flight was a decision regarding the weather. Thepilot knew there were going to be thunderstorms in thearea, but he had flown near thunderstorms before andnever had an accident.

Next, he let his desire to arrive at his destination ontime override his concern for a safe flight. For onething, in order to save time, he did not refuel the heli-copter, which might have allowed him the opportunityto circumnavigate the bad weather. Then he overesti-mated his flying abilities and decided to use a route thattook him through a potential area of thunderstormactivity. Next, the pilot pressed on into obviously dete-riorating conditions instead of changing course or landing prior to his destination.

On numerous occasions during the flight, the pilotcould have made effective decisions that may have pre-vented this accident. However, as the chain of eventsunfolded, each poor decision left him with fewer andfewer options. Making sound decisions is the key topreventing accidents. Traditional pilot training has

Human Factors—The study of howpeople interact with their environ-ments. In the case of general avia-tion, it is the study of how pilotperformance is influenced by suchissues as the design of cockpits, thefunction of the organs of the body,the effects of emotions, and theinteraction and communicationwith the other participants of theaviation community, such as othercrew members and air traffic con-trol personnel.

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emphasized flying skills, knowledge of the aircraft, andfamiliarity with regulations. ADM training focuses onthe decision-making process and the factors that affecta pilot’s ability to make effective choices.

ORIGINS OF ADM TRAININGThe airlines developed some of the first training pro-grams that focused on improving aeronautical decisionmaking. Human factors-related accidents motivated theairline industry to implement crew resource manage-ment (CRM) training for flight crews. The focus ofCRM programs is the effective use of all availableresources; human resources, hardware, and informa-tion. Human resources include all groups routinelyworking with the cockpit crew (or pilot) who areinvolved in decisions that are required to operate aflight safely. These groups include, but are not limited

to: ground personnel, dispatchers, cabin crewmembers,maintenance personnel, external-load riggers, and airtraffic controllers. Although the CRM concept origi-nated as airlines developed ways of facilitating crewcooperation to improve decision making in the cockpit,CRM principles, such as workload management, situa-tional awareness, communication, the leadership roleof the captain, and crewmember coordination havedirect application to the general aviation cockpit. Thisalso includes single pilot operations since pilots ofsmall aircraft, as well as crews of larger aircraft, mustmake effective use of all available resources—humanresources, hardware, and information. You can alsorefer to AC 60-22, Aeronautical Decision Making,which provides background references, definitions, andother pertinent information about ADM training in thegeneral aviation environment. [Figure 14-1]

DEFINITIONS

ADM is a systematic approach to the mental process used by pilots to consistently determine the best course of action in response to a given set of circumstances.

ATTITUDE is a personal motivational predisposition to respond to persons, situations, or events in a given manner that can, nevertheless, be changed or modified through training as sort of a mental shortcut to decision making.

ATTITUDE MANAGEMENT is the ability to recognize hazardous attitudes in oneself and the willingness to modify them as necessary through the application of an appropriate antidote thought.

HEADWORK is required to accomplish a conscious, rational thought process when making decisions. Good decision making involves risk identification and assessment, information processing, and problem solving.

JUDGMENT is the mental process of recognizing and analyzing all pertinent information in a particular situation, a rational evaluation of alternative actions in response to it, and a timely decision on which action to take.

PERSONALITY is the embodiment of personal traits and characteristics of an individual that are set at a very early age and extremely resistant to change.

POOR JUDGMENT CHAIN is a series of mistakes that may lead to an accident or incident. Two basic principles generally associated with the creation of a poor judgment chain are: (1) One bad decision often leads to another; and (2) as a string of bad decisions grows, it reduces the number of subsequent alternatives for continued safe flight. ADM is intended to break the poor judgment chain before it can cause an accident or incident.

RISK ELEMENTS IN ADM take into consideration the four fundamental risk elements: the pilot, the aircraft, the environment, and the type of operation that comprise any given aviation situation.

RISK MANAGEMENT is the part of the decision making process which relies on situational awareness, problem recognition, and good judgment to reduce risks associated with each flight.

SITUATIONAL AWARENESS is the accurate perception and understanding of all the factors and conditions within the four fundamental risk elements that affect safety before, during, and after the flight.

SKILLS and PROCEDURES are the procedural, psychomotor, and perceptual skills used to control a specific aircraft or its systems. They are the airmanship abilities that are gained through conventional training, are perfected, and become almost automatic through experience.

STRESS MANAGEMENT is the personal analysis of the kinds of stress experienced while flying, the application of appropriate stress assessment tools, and other coping mechanisms.

CREW RESOURCE MANAGEMENT (CRM) is the application of team management concepts in the flight deck environment. It was initially known as cockpit resource management, but as CRM programs evolved to include cabin crews, maintenance personnel, and others, the phrase crew resource management was adopted. This includes single pilots, as in most general aviation aircraft. Pilots of small aircraft, as well as crews of larger aircraft, must make effective use of all available resources; human resources, hardware, and information. A current definition includes all groups routinely working with the cockpit crew who are involved in decisions required to operate a flight safely. These groups include, but are not limited to: pilots, dispatchers, cabin crewmembers, maintenance personnel, and air traffic controllers. CRM is one way of addressing the challenge of optimizing the human/machine interface and accompanying interpersonal activities.

Figure 14-1. These terms are used in AC 60-22 to explain concepts used in ADM training.

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need to be taken to resolve the situation in the timeavailable. The expected outcome of each possibleaction should be considered and the risks assessedbefore you decide on a response to the situation.

Your first thought was to pull up on the collective andyank back on the cyclic, but after weighing the conse-quences of possibly losing rotor r.p.m. and not beingable to maintain the climb rate sufficiently enough toclear the canyon wall, which is now only a hundredyards away, you realize that your only course is to tryto turn back to the landing zone on the canyon floor.

IMPLEMENTING THE DECISION ANDEVALUATING THE OUTCOMEAlthough a decision may be reached and a course ofaction implemented, the decision-making process is notcomplete. It is important to think ahead and determinehow the decision could affect other phases of the flight.As the flight progresses, you must continue to evaluatethe outcome of the decision to ensure that it is produc-ing the desired result.

As you make your turn to the downwind, the airspeeddrops nearly to zero, and the helicopter becomes verydifficult to control. At this point, you must increase air-speed in order to maintain translational lift, but sincethe CG is aft of limits, you need to apply more forwardcyclic than usual. As you approach the landing zonewith a high rate of descent, you realize that you are in apotential settling-with-power situation if you try totrade airspeed for altitude and lose ETL. Therefore, youwill probably not be able to terminate the approach in ahover. You decide to make as shallow of an approach aspossible and perform a run-on landing.

The decision making process normally consists of sev-eral steps before you choose a course of action. To helpyou remember the elements of the decision-makingprocess, a six-step model has been developed using theacronym “DECIDE.” [Figure 14-2]

THE DECISION-MAKING PROCESSAn understanding of the decision-making process pro-vides you with a foundation for developing ADMskills. Some situations, such as engine failures, requireyou to respond immediately using established proce-dures with little time for detailed analysis. Traditionally,pilots have been well trained to react to emergencies,but are not as well prepared to make decisions thatrequire a more reflective response. Typically during aflight, you have time to examine any changes thatoccur, gather information, and assess risk before reach-ing a decision. The steps leading to this conclusion constitute the decision-making process.

DEFINING THE PROBLEMProblem definition is the first step in the decision-makingprocess. Defining the problem begins with recognizingthat a change has occurred or that an expected changedid not occur. A problem is perceived first by thesenses, then is distinguished through insight and expe-rience. These same abilities, as well as an objectiveanalysis of all available information, are used to deter-mine the exact nature and severity of the problem.

While doing a hover check after picking up fire fight-ers at the bottom of a canyon, you realize that you areonly 20 pounds under maximum gross weight. Whatyou failed to realize is that they had stowed some oftheir heaviest gear in the baggage compartment,which shifted the CG slightly behind the aft limits.Since weight and balance had never created any problems for you in the past, you did not bother to cal-culate CG and power required. You did, however, tryto estimate it by remembering the figures from earlierin the morning at the base camp. At a 5,000 foot density altitude and maximum gross weight, the per-formance charts indicated you had plenty of excesspower. Unfortunately, the temperature was 93°F andthe pressure altitude at the pick up point was 6,200feet (DA = 9,600 feet). Since there was enough powerfor the hover check, you felt there was sufficientpower to take off.

Even though the helicopter accelerated slowly duringthe takeoff, the distance between the helicopter and theground continued to increase. However, when youattempted to establish the best rate of climb speed, thenose wanted to pitch up to a higher than normal atti-tude, and you noticed that the helicopter was not gain-ing enough altitude in relation to the canyon wall acouple hundred yards ahead.

CHOOSING A COURSE OF ACTIONAfter the problem has been identified, you must evalu-ate the need to react to it and determine the actions that

Detect the fact that a change has occurred.

Estimate the need to counter or react to the change.

Choose a desirable outcome for the success of the flight.

Identify actions which could successfully control the change.

Do the necessary action to adapt to the change.

Evaluate the effect of the action.

DECIDE MODEL

Figure 14-2. The DECIDE model can provide a framework foreffective decision making.

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RISK MANAGEMENTDuring each flight, decisions must be made regardingevents that involve interactions between the four riskelements—the pilot in command, the aircraft, the envi-ronment, and the operation. The decision-makingprocess involves an evaluation of each of these risk ele-ments to achieve an accurate perception of the flightsituation. [Figure 14-3]

One of the most important decisions that a pilot in com-mand must make is the go/no-go decision. Evaluatingeach of these risk elements can help you decidewhether a flight should be conducted or continued. Letus evaluate the four risk elements and how they affectour decision making regarding the following situations.

Pilot—As a pilot, you must continually make decisionsabout your own competency, condition of health, mentaland emotional state, level of fatigue, and many othervariables. For example, you are called early in the morn-ing to make a long flight. You have had only a few hoursof sleep, and are concerned that the congestion you feelcould be the onset of a cold. Are you safe to fly?

Aircraft—You will frequently base decisions on yourevaluations of the aircraft, such as its powerplant, per-formance, equipment, fuel state, or airworthiness. Pictureyourself in this situation: you are en route to an oil rig anhour’s flight from shore, and you have just passed theshoreline. Then you notice the oil temperature at the highend of the caution range. Should you continue out to sea,or return to the nearest suitable heliport/airport?

Environment—This encompasses many elements notpilot or aircraft related. It can include such factors asweather, air traffic control, navaids, terrain, takeoff and

Risk Elements—The four compo-nents of a flight that make up theoverall situation.

NTSB—National TransportationSafety Board.

landing areas, and surrounding obstacles. Weather isone element that can change drastically over time anddistance. Imagine you are ferrying a helicopter crosscountry and encounter unexpected low clouds and rainin an area of rising terrain. Do you try to stay underthem and “scud run,” or turn around, stay in the clear,and obtain current weather information?

Operation—The interaction between you as the pilot,your aircraft, and the environment is greatly influencedby the purpose of each flight operation. You must eval-uate the three previous areas to decide on the desirabil-ity of undertaking or continuing the flight as planned. Itis worth asking yourself why the flight is being made,how critical is it to maintain the schedule, and is thetrip worth the risks? For instance, you are tasked to takesome technicians into rugged mountains for a routinesurvey, and the weather is marginal. Would it be prefer-able to wait for better conditions to ensure a safe flight?How would the priorities change if you were tasked tosearch for cross-country skiers who had become lost indeep snow and radioed for help?

ASSESSING RISKExamining NTSB reports and other accident researchcan help you to assess risk more effectively. For exam-ple, the accident rate decreases by nearly 50 percent oncea pilot obtains 100 hours, and continues to decrease untilthe 1,000 hour level. The data suggest that for the first500 hours, pilots flying VFR at night should establishhigher personal limitations than are required by the reg-ulations and, if applicable, apply instrument flying skillsin this environment. [Figure 14-4]

Studies also indicate the types of flight activities thatare most likely to result in the most serious accidents.The majority of fatal general aviation accident causesfall under the categories of maneuvering flight,approaches, takeoff/initial climb, and weather. Delvingdeeper into accident statistics can provide some impor-tant details that can help you to understand the risksinvolved with specific flying situations. For example,maneuvering flight is one of the largest single produc-

Figure 14-3. When situationally aware, you have an overview of the total operation and are not fixated on one perceived signifi-cant factor.

RISK ELEMENTSPilot Aircraft Environment Operation

Factors, such as weather, airport conditions, and the availability of air traffic control services must be examined.

The aircraft's performance, limitations, equipment, and airworthiness must be deter- mined.

The pilot's fitness to fly must be evaluated including competency in the aircraft, currency, and flight experience.

To maintain situational awareness, an accurate perception must be attained of how the pilot, aircraft, environment, and operation combine to affect the flight.

Situation

The purpose of the flight is a factor which influences the pilot's decision on undertaking or continuing the flight.

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ers of fatal accidents. Fatal accidents, which occur during approach, often happen at night or in IFR condi-tions. Takeoff/initial climb accidents frequently are dueto the pilot’s lack of awareness of the effects of densityaltitude on aircraft performance or other improper take-off planning resulting in loss of control during, orshortly after takeoff. The majority of weather-relatedaccidents occur after attempted VFR flight into IFRconditions.

FACTORS AFFECTING DECISIONMAKINGIt is important to point out the fact that being familiarwith the decision-making process does not ensure thatyou will have the good judgment to be a safe pilot. Theability to make effective decisions as pilot in command depends on a number of factors. Some circumstances, such as the time available to make adecision, may be beyond your control. However, youcan learn to recognize those factors that can be man-aged, and learn skills to improve decision-makingability and judgment.

PILOT SELF-ASSESSMENTThe pilot in command of an aircraft is directly responsi-ble for, and is the final authority as to, the operation ofthat aircraft. In order to effectively exercise that respon-sibility and make effective decisions regarding the outcome of a flight, you must have an understanding ofyour limitations. Your performance during a flight isaffected by many factors, such as health, recency ofexperience, knowledge, skill level, and attitude.

Exercising good judgment begins prior to taking thecontrols of an aircraft. Often, pilots thoroughly checktheir aircraft to determine airworthiness, yet do notevaluate their own fitness for flight. Just as a checklist

is used when preflighting an aircraft, a personalchecklist based on such factors as experience, cur-rency, and comfort level can help determine if you areprepared for a particular flight. Specifying whenrefresher training should be accomplished and desig-nating weather minimums, which may be higher thanthose listed in Title 14 of the Code of FederalRegulations (14 CFR) part 91, are elements that maybe included on a personal checklist. In addition to areview of personal limitations, you should use the I’MSAFE Checklist to further evaluate your fitness forflight. [Figure 14-5]

RECOGNIZING HAZARDOUS ATTITUDESBeing fit to fly depends on more than just your physi-cal condition and recency of experience. For example,attitude affects the quality of your decisions. Attitudecan be defined as a personal motivational predisposi-tion to respond to persons, situations, or events in agiven manner. Studies have identified five hazardousattitudes that can interfere with your ability to makesound decisions and exercise authority properly.[Figure 14-6]

Hazardous attitudes can lead to poor decision makingand actions that involve unnecessary risk. You mustexamine your decisions carefully to ensure that yourchoices have not been influenced by hazardous attitudes, and you must be familiar with positive alter-natives to counteract the hazardous attitudes. Thesesubstitute attitudes are referred to as antidotes. Duringa flight operation, it is important to be able to recognize

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Figure 14-4. Statistical data can identify operations that havemore risk. Illness—Do I have any symptoms?

Medication—Have I been taking prescription or over-the-counter drugs?

Stress—Am I under psychological pressure from the job? Worried about financial matters, health problems, or family discord?

Fatigue—Am I tired and not adequately rested?

Eating—Am I adequately nourished?

Alcohol—Have I been drinking within 8 hours? Within 24 hours?

I'M SAFE CHECKLIST

Figure 14-5. Prior to flight, you should assess your fitness,just as you evaluate the aircraft’s airworthiness.

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a hazardous attitude, correctly label the thought, andthen recall its antidote. [Figure 14-7]

STRESS MANAGEMENTEveryone is stressed to some degree all the time. A cer-tain amount of stress is good since it keeps a personalert and prevents complacency. However, effects ofstress are cumulative and, if not coped with adequately,they eventually add up to an intolerable burden.Performance generally increases with the onset ofstress, peaks, and then begins to fall off rapidly as stresslevels exceed a person’s ability to cope. The ability tomake effective decisions during flight can be impairedby stress. Factors, referred to as stressors, can increasea pilot’s risk of error in the cockpit. [Figure 14-8]

There are several techniques to help manage the accu-mulation of life stresses and prevent stress overload.For example, including relaxation time in a busy sched-ule and maintaining a program of physical fitness canhelp reduce stress levels. Learning to manage timemore effectively can help you avoid heavy pressuresimposed by getting behind schedule and not meetingdeadlines. Take an assessment of yourself to determineyour capabilities and limitations and then set realisticgoals. In addition, avoiding stressful situations andencounters can help you cope with stress.

USE OF RESOURCESTo make informed decisions during flight operations,you must be aware of the resources found both insideand outside the cockpit. Since useful tools and sourcesof information may not always be readily apparent,learning to recognize these resources is an essentialpart of ADM training. Resources must not only be iden-

THE FIVE HAZARDOUS ATTITUDES

1. Anti-Authority: "Don't tell me."

This attitude is found in people who do not like anyone telling them what to do. In a sense, they are saying, "No one can tell me what to do." They may be resentful of having someone tell them what to do, or may regard rules, regulations, and procedures as silly or unnecessary. However, it is always your prerogative to question authority if you feel it is in error. This is the attitude of people who frequently feel the need to do something, anything, immediately. They do not stop to think about what they are about to do; they do not select the best alternative, and they do the first thing that comes to mind. Many people feel that accidents happen to others, but never to them. They know accidents can happen, and they know that anyone can be affected. They never really feel or believe that they will be personally involved. Pilots who think this way are more likely to take chances and increase risk. Pilots who are always trying to prove that they are better than anyone else are thinking, "I can do it –I'll show them." Pilots with this type of attitude will try to prove themselves by taking risks in order to impress others. While this pattern is thought to be a male characteristic, women are equally susceptible. Pilots who think, "What's the use?" do not see themselves as being able to make a great deal of difference in what happens to them. When things go well, the pilot is apt to think that it is good luck. When things go badly, the pilot may feel that someone is out to get me, or attribute it to bad luck. The pilot will leave the action to others, for better or worse. Sometimes, such pilots will even go along with unreasonable requests just to be a "nice guy."

2. Impulsivity: "Do it quickly."

3. Invulnerability: "It won't happen to me."

4. Macho: "I can do it."

5. Resignation:

"What's the use?"

Figure 14-6. You should examine your decisions carefully to ensure that your choices have not been influenced by a hazardousattitude.

Taking chances is foolish.

Follow the rules. They are usually right.

It could happen to me.

Not so fast. Think first.

I'm not helpless. I can make a difference.

HAZARDOUS ATTITUDES ANTIDOTES

Macho—Brenda often brags to her friends about her skills as a pilot and wants to impress them with her abilities. During her third solo flight she decides to take a friend for a helicopter ride. Anti-authority—In the air she thinks "It'sgreat to be up here without an instructor criticizing everything I do. His do-it-by-the-book attitude takes all of the fun out of flying." Invulnerability—As she nears her friends farm, she remembers that it is about eight miles from the closest airport. She thinks, "I'll land in the pasture behind the barn at Sarah's farm. It won't be dangerous at all... the pasture is fenced and mowed and no animals are in the way. It's no more dangerous than landing at a heliport." Impulsivity—After a short look, Brenda initiates an approach to her friend's pasture. Not realizing that she is landing with a tail wind, she makes a hard landing in the pasture and nearly hits the fence with the tail rotor before she gets the helicopter stopped. Resignation—A policeman pulls up to investigate what he believes to be an emergency landing. As Brenda is walking from the helicopter, she is supprised that anyone observed her landing. Her first thought is "if it weren't for my bad luck, this policeman wouldn't have come along and this would have been a great afternoon."

Figure 14-7. You must be able to identify hazardous attitudesand apply the appropriate antidote when needed.

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tified, but you must develop the skills to evaluatewhether you have the time to use a particular resourceand the impact that its use will have upon the safety offlight. For example, the assistance of ATC may be veryuseful if you are lost. However, in an emergency situa-tion when action needs be taken quickly, time may notbe available to contact ATC immediately.

INTERNAL RESOURCESInternal resources are found in the cockpit duringflight. Since some of the most valuable internalresources are ingenuity, knowledge, and skill, you canexpand cockpit resources immensely by improvingthese capabilities. This can be accomplished by fre-quently reviewing flight information publications, suchas the CFRs and the AIM, as well as by pursuing addi-tional training.

A thorough understanding of all the equipment and sys-tems in the aircraft is necessary to fully utilize allresources. For example, advanced navigation andautopilot systems are valuable resources. However, ifpilots do not fully understand how to use this equip-ment, or they rely on it so much that they become complacent, it can become a detriment to safe flight.

Checklists are essential cockpit resources for verifyingthat the aircraft instruments and systems are checked,set, and operating properly, as well as ensuring that theproper procedures are performed if there is a systemmalfunction or in-flight emergency. In addition, theFAA-approved rotorcraft flight manual, which isrequired to be carried on board the aircraft, is essentialfor accurate flight planning and for resolving in-flightequipment malfunctions. Other valuable cockpitresources include current aeronautical charts, and pub-lications, such as the Airport/Facility Directory.

Passengers can also be a valuable resource. Passengerscan help watch for traffic and may be able to provide

information in an irregular situation, especially if theyare familiar with flying. A strange smell or sound mayalert a passenger to a potential problem. As pilot incommand, you should brief passengers before theflight to make sure that they are comfortable voicingany concerns.

EXTERNAL RESOURCESPossibly the greatest external resources during flightare air traffic controllers and flight service specialists.ATC can help decrease pilot workload by providingtraffic advisories, radar vectors, and assistance in emer-gency situations. Flight service stations can provideupdates on weather, answer questions about airportconditions, and may offer direction-finding assistance.The services provided by ATC can be invaluable inenabling you to make informed in-flight decisions.

WORKLOAD MANAGEMENTEffective workload management ensures that essentialoperations are accomplished by planning, prioritizing,and sequencing tasks to avoid work overload. Asexperience is gained, you learn to recognize futureworkload requirements and can prepare for highworkload periods during times of low workload.Reviewing the appropriate chart and setting radio fre-quencies well in advance of when they are neededhelps reduce workload as your flight nears the airport.In addition, you should listen to ATIS, ASOS, orAWOS, if available, and then monitor the tower fre-quency or CTAF to get a good idea of what trafficconditions to expect. Checklists should be performedwell in advance so there is time to focus on traffic andATC instructions. These procedures are especiallyimportant prior to entering a high-density traffic area,such as Class B airspace.

To manage workload, items should be prioritized. Forexample, during any situation, and especially in anemergency, you should remember the phrase “aviate,

STRESSORS

Physical Stress—Conditions associated with the environment, such as temperature and humidity extremes, noise, vibration, and lack of oxygen.

Physiological Stress—Physical conditions, such as fatigue, lack of physical fitness, sleep loss, missed meals (leading to low blood sugar levels), and illness.

Psychological Stress—Social or emotional factors, such as a death in the family, a divorce, a sick child, or a demotion at work. This type of stress may also be related to mental workload, such as analyzing a problem, navigating an aircraft, or making decisions.

Figure 14-8. The three types of stressors that can affect a pilot’s performance.

14-8

navigate, and communicate.” This means that the firstthing you should do is make sure the helicopter is under

control. Then begin flying to an acceptable landingarea. Only after the first two items are assured, shouldyou try to communicate with anyone.

Another important part of managing workload is rec-ognizing a work overload situation. The first effect ofhigh workload is that you begin to work faster. Asworkload increases, attention cannot be devoted to sev-eral tasks at one time, and you may begin to focus onone item. When you become task saturated, there is noawareness of inputs from various sources, so decisionsmay be made on incomplete information, and the pos-sibility of error increases. [Figure 14-9]

When becoming overloaded, you should stop, think,slow down, and prioritize. It is important that youunderstand options that may be available to decreaseworkload. For example, tasks, such as locating an itemon a chart or setting a radio frequency, may be dele-gated to another pilot or passenger, an autopilot, ifavailable, may be used, or ATC may be enlisted to provide assistance.

SITUATIONAL AWARENESSSituational awareness is the accurate perception of theoperational and environmental factors that affect theaircraft, pilot, and passengers during a specific periodof time. Maintaining situational awareness requiresan understanding of the relative significance of thesefactors and their future impact on the flight. When sit-uationally aware, you have an overview of the totaloperation and are not fixated on one perceived signif-icant factor. Some of the elements inside the aircraftto be considered are the status of aircraft systems, youas the pilot, and passengers. In addition, an awareness

of the environmental conditions of the flight, such asspatial orientation of the helicopter, and its relation-ship to terrain, traffic, weather, and airspace must bemaintained.

To maintain situational awareness, all of the skillsinvolved in aeronautical decision making are used. Forexample, an accurate perception of your fitness can beachieved through self-assessment and recognition ofhazardous attitudes. A clear assessment of the status ofnavigation equipment can be obtained through work-load management, and establishing a productive relationship with ATC can be accomplished by effec-tive resource use.

OBSTACLES TO MAINTAINING SITUATIONALAWARENESSFatigue, stress, and work overload can cause you to fix-ate on a single perceived important item rather thanmaintaining an overall awareness of the flight situa-tion. A contributing factor in many accidents is a distraction that diverts the pilot’s attention from moni-toring the instruments or scanning outside the aircraft. Many cockpit distractions begin as a minorproblem, such as a gauge that is not reading correctly,but result in accidents as the pilot diverts attention tothe perceived problem and neglects to properly controlthe aircraft.

Complacency presents another obstacle to maintainingsituational awareness. When activities become routine,you may have a tendency to relax and not put as mucheffort into performance. Like fatigue, complacencyreduces your effectiveness in the cockpit. However,complacency is harder to recognize than fatigue, sinceeverything is perceived to be progressing smoothly. Forexample, you have just dropped off another group offire fighters for the fifth time that day. Without think-ing, you hastily lift the helicopter off the ground, notrealizing that one of the skids is stuck between tworocks. The result is dynamic rollover and a destroyedhelicopter.

OPERATIONAL PITFALLSThere are a number of classic behavioral traps intowhich pilots have been known to fall. Pilots, particu-larly those with considerable experience, as a rule,always try to complete a flight as planned, please pas-sengers, and meet schedules. The basic drive to meetor exceed goals can have an adverse effect on safety,and can impose an unrealistic assessment of pilotingskills under stressful conditions. These tendencies ulti-mately may bring about practices that are dangerousand often illegal, and may lead to a mishap. You willdevelop awareness and learn to avoid many of theseoperational pitfalls through effective ADM training.[Figure 14-10]

Margin of Safety

Pilot Capabilities

Task Requirements

Preflight Takeoff

Cruise Approach & Landing

Taxi Taxi Time

Figure 14-9. Accidents often occur when flying task require-ments exceed pilot capabilities. The difference betweenthese two factors is called the margin of safety. Note that inthis idealized example, the margin of safety is minimal duringthe approach and landing. At this point, an emergency or dis-traction could overtax pilot capabilities, causing an accident.

14-9

Peer Pressure—Poor decision making may be based upon an emotional response to peers, rather than evaluating a situation objectively.

Mind Set—A pilot displays mind set through an inability to recognize and cope with changes in a given situation.

Get-There-Itis—This disposition impairs pilot judgment through a fixation on the original goal or destination, combined with a disregard for any alternative course of action.

Scud Running—This occurs when a pilot tries to maintain visual contact with the terrain at low altitudes while instrument conditions exist.

Continuing Visual Flight Rules (VFR) into Instrument Conditions—Spatial disorientation or collision with ground/obstacles may occur when a pilot continues VFR into instrument conditions. This can be even more dangerous if the pilot is not instrument-rated or current.

Getting Behind the Aircraft—This pitfall can be caused by allowing events or the situation to control pilot actions. A constant state of surprise at what happens next may be exhibited when the pilot is getting behind the aircraft.

Loss of Positional or Situational Awareness—In extreme cases, when a pilot gets behind the aircraft, a loss of positional or situational awareness may result. The pilot may not know the aircraft's geographical location, or may be unable to recognize deteriorating circumstances.

Operating Without Adequate Fuel Reserves—Ignoring minimum fuel reserve requirements is generally the result of overconfidence, lack of flight planning, or disregarding applicable regulations.

Flying Outside the Envelope—The assumed high performance capability of a particular aircraft may cause a mistaken belief that it can meet the demands imposed by a pilot's overestimated flying skills.

Neglect of Flight Planning, Preflight Inspections, and Checklists—A pilot may rely on short- and long-term memory, regular flying skills, and familiar routes instead of established procedures and published checklists. This can be particularly true of experienced pilots.

OPERATIONAL PITFALLS

Figure 14-10. All experienced pilots have fallen prey to, or have been tempted by, one or more of these tendencies in their flyingcareers.

14-10

autorotation. The first successful example of this typeof aircraft was the British Fairy Rotodyne, certificatedto the Transport Category in 1958. During the 1960sand 1970s, the popularity of gyroplanes increased withthe certification of the McCulloch J-2 and Umbaugh.The latter becoming the Air & Space 18A.

There are several aircraft under development using thefree spinning rotor to achieve rotary wing takeoff per-formance and fixed wing cruise speeds. The gyroplaneoffers inherent safety, simplicity of operation, and out-standing short field point-to-point capability.

TYPES OF GYROPLANESBecause the free spinning rotor does not require anantitorque device, a single rotor is the predominateconfiguration. Counter-rotating blades do not offerany particular advantage. The rotor system used in agyroplane may have any number of blades, but themost popular are the two and three blade systems.Propulsion for gyroplanes may be either tractor orpusher, meaning the engine may be mounted on thefront and pull the aircraft, or in the rear, pushing itthrough the air. The powerplant itself may be eitherreciprocating or turbine. Early gyroplanes wereoften a derivative of tractor configured airplaneswith the rotor either replacing the wing or acting inconjunction with it. However, the pusher configura-tion is generally more maneuverable due to theplacement of the rudder in the propeller slipstream,and also has the advantage of better visibility for thepilot. [Figure 15-1]

15-1

January 9th, 1923, marked the first officially observedflight of an autogyro. The aircraft, designed by Juan dela Cierva, introduced rotor technology that made for-ward flight in a rotorcraft possible. Until that time,rotary-wing aircraft designers were stymied by theproblem of a rolling moment that was encounteredwhen the aircraft began to move forward. This rollingmoment was the product of airflow over the rotor disc,causing an increase in lift of the advancing blade anddecrease in lift of the retreating blade. Cierva’s success-ful design, the C.4, introduced the articulated rotor, onwhich the blades were hinged and allowed to flap. Thissolution allowed the advancing blade to move upward,decreasing angle of attack and lift, while the retreatingblade would swing downward, increasing angle ofattack and lift. The result was balanced lift across therotor disc regardless of airflow. This breakthrough wasinstrumental in the success of the modern helicopter,which was developed over 15 years later. (For moreinformation on dissymmetry of lift, refer to Chapter 3—Aerodynamics of Flight.) On April 2, 1931, the PitcairnPCA-2 autogyro was granted Type Certificate No. 410and became the first rotary wing aircraft to be certifiedin the United States. The term “autogyro” was used todescribe this type of aircraft until the FAA later desig-nated them “gyroplanes.”

By definition, the gyroplane is an aircraft that achieveslift by a free spinning rotor. Several aircraft have usedthe free spinning rotor to attain performance not avail-able in the pure helicopter. The “gyrodyne” is a hybridrotorcraft that is capable of hovering and yet cruises in

Figure 15-1. The gyroplane may have wings, be either tractor or pusher configured, and could be turbine or propeller powered.Pictured are the Pitcairn PCA-2 Autogyro (left) and the Air & Space 18A gyroplane.

15-2

When direct control of the rotor head was perfected,the jump takeoff gyroplane was developed. Under theproper conditions, these gyroplanes have the ability tolift off vertically and transition to forward flight. Laterdevelopments have included retaining the direct con-trol rotor head and utilizing a wing to unload the rotor,which results in increased forward speed.

COMPONENTSAlthough gyroplanes are designed in a variety of config-urations, for the most part the basic components are thesame. The minimum components required for a func-tional gyroplane are an airframe, a powerplant, a rotorsystem, tail surfaces, and landing gear. [Figure 15-2] Anoptional component is the wing, which is incorporatedinto some designs for specific performance objectives.

AIRFRAMEThe airframe provides the structure to which all othercomponents are attached. Airframes may be weldedtube, sheet metal, composite, or simply tubes boltedtogether. A combination of construction methods mayalso be employed. The airframes with the greateststrength-to-weight ratios are a carbon fiber material or

Powerplant

Rotor

Airframe

Landing Gear

Tail Surfaces

Direct Control—The capacity forthe pilot to maneuver the aircraftby tilting the rotor disc and, onsome gyroplanes, affect changes inpitch to the rotor blades. Theseequate to cyclic and collective con-trol, which were not available inearlier autogyros.

Unload—To reduce the compo-nent of weight supported by therotor system.

Prerotate—Spinning a gyroplanerotor to sufficient r.p.m. prior toflight.

the welded tube structure, which has been in use for anumber of years.

POWERPLANTThe powerplant provides the thrust necessary for forwardflight, and is independent of the rotor system while inflight. While on the ground, the engine may be used asa source of power to prerotate the rotor system. Overthe many years of gyroplane development, a widevariety of engine types have been adapted to the gyro-plane. Automotive, marine, ATV, and certificated aircraft engines have all been used in various gyroplane designs. Certificated gyroplanes arerequired to use FAA certificated engines. The cost of anew certificated aircraft engine is greater than the costof nearly any other new engine. This added cost is theprimary reason other types of engines are selected foruse in amateur built gyroplanes.

ROTOR SYSTEMThe rotor system provides lift and control for the gyro-plane. The fully articulated and semi-rigid teeteringrotor systems are the most common. These areexplained in-depth in Chapter 5—Main Rotor System.The teeter blade with hub tilt control is most commonin homebuilt gyroplanes. This system may also employa collective control to change the pitch of the rotorblades. With sufficient blade inertia and collectivepitch change, jump takeoffs can be accomplished.

TAIL SURFACESThe tail surfaces provide stability and control in the pitchand yaw axes. These tail surfaces are similar to an air-plane empennage and may be comprised of a fin andrudder, stabilizer and elevator. An aft mounted ductenclosing the propeller and rudder has also been used.Many gyroplanes do not incorporate a horizontal tail surface.

On some gyroplanes, especially those with an enclosedcockpit, the yaw stability is marginal due to the largefuselage side area located ahead of the center of grav-ity. The additional vertical tail surface necessary tocompensate for this instability is difficult to achieve asthe confines of the rotor tilt and high landing pitch atti-tude limits the available area. Some gyroplane designsincorporate multiple vertical stabilizers and rudders toadd additional yaw stability.

Figure 15-2. Gyroplanes typically consist of five major com-ponents. A sixth, the wing, is utilized on some designs.

15-3

LANDING GEARThe landing gear provides the mobility while on theground and may be either conventional or tricycle.Conventional gear consists of two main wheels, and oneunder the tail. The tricycle configuration also uses twomains, with the third wheel under the nose. Early auto-gyros, and several models of gyroplanes, use conven-tional gear, while most of the later gyroplanesincorporate tricycle landing gear. As with fixed wingaircraft, the gyroplane landing gear provides the groundmobility not found in most helicopters.

WINGSWings may or may not comprise a component of thegyroplane. When used, they provide increased per-formance, increased storage capacity, and increasedstability. Gyroplanes are under development withwings that are capable of almost completely unload-ing the rotor system and carrying the entire weight

of the aircraft. This will allow rotary wing takeoffperformance with fixed wing cruise speeds. [Figure15-3]

Figure 15-3. The CarterCopter uses wings to enhanceperformance.

15-4

16-1

Helicopters and gyroplanes both achieve lift throughthe use of airfoils, and, therefore, many of the basicaerodynamic principles governing the production of liftapply to both aircraft. These concepts are explained indepth in Chapter 2—General Aerodynamics, and con-stitute the foundation for discussing the aerodynamicsof a gyroplane.

AUTOROTATIONA fundamental difference between helicopters andgyroplanes is that in powered flight, a gyroplane rotorsystem operates in autorotation. This means the rotorspins freely as a result of air flowing up through theblades, rather than using engine power to turn theblades and draw air from above. [Figure 16-1] Forcesare created during autorotation that keep the rotorblades turning, as well as creating lift to keep the air-craft aloft. Aerodynamically, the rotor system of agyroplane in normal flight operates like a helicopterrotor during an engine-out forward autorotativedescent.

VERTICAL AUTOROTATIONDuring a vertical autorotation, two basic componentscontribute to the relative wind striking the rotor blades.[Figure 16-2] One component, the upward flow of airthrough the rotor system, remains relatively constant

for a given flight condition. The other component is therotational airflow, which is the wind velocity across theblades as they spin. This component varies signifi-cantly based upon how far from the rotor hub it ismeasured. For example, consider a rotor disc that is 25feet in diameter operating at 300 r.p.m. At a point onefoot outboard from the rotor hub, the blades are travel-ing in a circle with a circumference of 6.3 feet. Thisequates to 31.4 feet per second (f.p.s.), or a rotationalblade speed of 21 m.p.h. At the blade tips, the circum-ference of the circle increases to 78.5 feet. At the sameoperating speed of 300 r.p.m., this creates a blade tip

Direction of Flight

Relative Wind Relative Wind

Direction of Flight

Figure 16-1. Airflow through the rotor system on a gyroplane is reversed from that on a powered helicopter. This airflow is themedium through which power is transferred from the gyroplane engine to the rotor system to keep it rotating.

Resultant Relative Wind

Wind due to Blade Rotation

Upward Airflow

Figure 16-2. In a vertical autorotation, the wind from the rotation of the blade combines with the upward airflow toproduce the resultant relative wind striking the airfoil.

16-2

speed of 393 feet per second, or 267 m.p.h. The resultis a higher total relative wind, striking the blades at alower angle of attack. [Figure 16-3]

ROTOR DISC REGIONSAs with any airfoil, the lift that is created by rotorblades is perpendicular to the relative wind. Becausethe relative wind on rotor blades in autorotation shiftsfrom a high angle of attack inboard to a lower angle ofattack outboard, the lift generated has a higher forwardcomponent closer to the hub and a higher vertical com-ponent toward the blade tips. This creates distinctregions of the rotor disc that create the forces neces-sary for flight in autorotation. [Figure 16-4] Theautorotative region, or driving region, creates a totalaerodynamic force with a forward component thatexceeds all rearward drag forces and keeps the bladesspinning. The propeller region, or driven region, gen-erates a total aerodynamic force with a higher verticalcomponent that allows the gyroplane to remain aloft.Near the center of the rotor disc is a stall region wherethe rotational component of the relative wind is so lowthat the resulting angle of attack is beyond the stalllimit of the airfoil. The stall region creates drag againstthe direction of rotation that must be overcome by theforward acting forces generated by the driving region.

AUTOROTATION IN FORWARD FLIGHTAs discussed thus far, the aerodynamics of autorotationapply to a gyroplane in a vertical descent. Becausegyroplanes are normally operated in forward flight, thecomponent of relative wind striking the rotor blades asa result of forward speed must also be considered. Thiscomponent has no effect on the aerodynamic principlesthat cause the blades to autorotate, but causes a shift inthe zones of the rotor disc.

As a gyroplane moves forward through the air, the for-ward speed of the aircraft is effectively added to the

Resultant Relative Wind

Rotational Airflow (267 m.p.h. or 393 f.p.s.)

Upward Airflow (17 m.p.h. or 25 f.p.s.)

TIP

Rotor Speed: 300 r.p.m.

F

Resultant

Relative WindRotational Airflow

(21 m.p.h. or 31 f.p.s.)

Upward Airflow (17 m.p.h. or 25 f.p.s.)

HUB

VERTICAL AUTOROTATION

Figure 16-3. Moving outboard on the rotor blade, the rotational velocity increasingly exceeds the upward component of airflow,resulting in a higher relative wind at a lower angle of attack.

Driven Region

Driving Region

Stall

Region

Driven Region (Propeller)

Driving Region (Autorotative)

Stall Region

F

VERTICAL AUTOROTATION

Rotational Relative Wind

LiftLift

TAFTAF

Total Aerodynamic Force Aft of Axis of Rotation

Drag

Chord LineInflow Up Through Rotor Resultant

Relative Wind

Total Aerodynamic Force Forward of Axis of Rotation

Drag

Inflow

Axis of Rotation

Axis of Rotation

Axis of Rotation

(Blade is Stalled)

TAF

Drag

Inflow

Lift

Figure 16-4. The total aerodynamic force is aft of the axis ofrotation in the driven region and forward of the axis of rota-tion in the driving region. Drag is the major aerodynamicforce in the stall region. For a complete depiction of forcevectors during a vertical autorotation, refer to Chapter 3—Aerodynamics of Flight (Helicopter), Figure 3-22.

16-3

relative wind striking the advancing blade, and sub-tracted from the relative wind striking the retreatingblade. To prevent uneven lifting forces on the two sidesof the rotor disc, the advancing blade teeters up,decreasing angle of attack and lift, while the retreatingblade teeters down, increasing angle of attack and lift.(For a complete discussion on dissymmetry of lift, referto Chapter 3—Aerodynamics of Flight.) The lowerangles of attack on the advancing blade cause more ofthe blade to fall in the driven region, while higherangles of attack on the retreating blade cause more ofthe blade to be stalled. The result is a shift in the rotorregions toward the retreating side of the disc to a degreedirectly related to the forward speed of the aircraft.[Figure 16-5]

REVERSE FLOWOn a rotor system in forward flight, reverse flow occursnear the rotor hub on the retreating side of the rotordisc. This is the result of the forward speed of the air-craft exceeding the rotational speed of the rotor blades.For example, two feet outboard from the rotor hub, theblades travel in a circle with a circumference of 12.6feet. At a rotor speed of 300 r.p.m., the blade speed atthe two-foot station is 42 m.p.h. If the aircraft is beingoperated at a forward speed of 42 m.p.h., the forwardspeed of the aircraft essentially negates the rotationalvelocity on the retreating blade at the two-foot station.Moving inboard from the two-foot station on theretreating blade, the forward speed of the aircraftincreasingly exceeds the rotational velocity of theblade. This causes the airflow to actually strike thetrailing edge of the rotor blade, with velocity increas-ing toward the rotor hub. [Figure 16-6] The size of thearea that experiences reverse flow is dependent prima-

rily on the forward speed of the aircraft, with higherspeed creating a larger region of reverse flow. To somedegree, the operating speed of the rotor system also hasan effect on the size of the region, with systems operat-ing at lower r.p.m. being more susceptible to reverseflow and allowing a greater portion of the blade toexperience the effect.

RETREATING BLADE STALLThe retreating blade stall in a gyroplane differs fromthat of a helicopter in that it occurs outboard from therotor hub at the 20 to 40 percent position rather than atthe blade tip. Because the gyroplane is operating inautorotation, in forward flight there is an inherent stallregion centered inboard on the retreating blade. [Referto figure 16-5] As forward speed increases, the angle ofattack on the retreating blade increases to prevent dis-symmetry of lift and the stall region moves further outboard on the retreating blade. Because the stalledportion of the rotor disc is inboard rather than near thetip, as with a helicopter, less force is created about theaircraft center of gravity. The result is that you may feela slight increase in vibration, but you would not experi-ence a large pitch or roll tendency.

ROTOR FORCEAs with any heavier than air aircraft, the four forcesacting on the gyroplane in flight are lift, weight, thrustand drag. The gyroplane derives lift from the rotor and

Forward

Driven Region

Driving Region

Stall

Region

Retreating Side

Advancing Side

Figure 16-5. Rotor disc regions in forward autorotative flight.

Forward Flight at

42 kt

42kt

42kt

42kt

42kt

2'

Area of Reverse flow

42kt

Rotor Speed 300 r.p.m.

Figure 16-6. An area of reverse flow forms on the retreatingblade in forward flight as a result of aircraft speed exceedingblade rotational speed.

16-4

rotor blades turn, rapid changes occur on the airfoilsdepending on position, rotor speed, and aircraft speed.A change in the angle of attack of the rotor disc caneffect a rapid and substantial change in total rotor drag.

Rotor drag can be divided into components of induceddrag and profile drag. The induced drag is a product oflift, while the profile drag is a function of rotor r.p.m.Because induced drag is a result of the rotor providinglift, profile drag can be considered the drag of the rotorwhen it is not producing lift. To visualize profile drag,consider the drag that must be overcome to prerotatethe rotor system to flight r.p.m. while the blades areproducing no lift. This can be achieved with a rotor sys-tem having a symmetrical airfoil and a pitch changecapability by setting the blades to a 0° angle of attack.A rotor system with an asymmetrical airfoil and a builtin pitch angle, which includes most amateur-builtteeter-head rotor systems, cannot be prerotated withouthaving to overcome the induced drag created as well.

THRUSTThrust in a gyroplane is defined as the component oftotal propeller force parallel to the relative wind. Aswith any force applied to an aircraft, thrust acts aroundthe center of gravity. Based upon where the thrust isapplied in relation to the aircraft center of gravity, a rel-atively small component may be perpendicular to therelative wind and can be considered to be additive tolift or weight.

In flight, the fuselage of a gyroplane essentially acts asa plumb suspended from the rotor, and as such, it is

thrust directly from the engine through a propeller.[Figure 16-7]

The force produced by the gyroplane rotor may bedivided into two components; rotor lift and rotor drag.The component of rotor force perpendicular to theflight path is rotor lift, and the component of rotor forceparallel to the flight path is rotor drag. To derive thetotal aircraft drag reaction, you must also add the dragof the fuselage to that of the rotor.

ROTOR LIFTRotor lift can most easily be visualized as the liftrequired to support the weight of the aircraft. When anairfoil produces lift, induced drag is produced. Themost efficient angle of attack for a given airfoil pro-duces the most lift for the least drag. However, the air-foil of a rotor blade does not operate at this efficientangle throughout the many changes that occur in eachrevolution. Also, the rotor system must remain in theautorotative (low) pitch range to continue turning inorder to generate lift.

Some gyroplanes use small wings for creating lift whenoperating at higher cruise speeds. The lift provided bythe wings can either supplement or entirely replacerotor lift while creating much less induced drag.

ROTOR DRAGTotal rotor drag is the summation of all the drag forcesacting on the airfoil at each blade position. Each bladeposition contributes to the total drag according to thespeed and angle of the airfoil at that position. As the

Lift

Resultant

Thrust

Resultant

Thrust

Lift

Result

ant

Drag

Rotor Drag

Fuselage Drag

Result

ant

Wei

ght

Wei

ght

Figure 16-7. Unlike a helicopter, in forward powered flight the resultant rotor force of a gyroplane acts in a rearward direction.

16-5

subject to pendular action in the same way as a heli-copter. Unlike a helicopter, however, thrust is applieddirectly to the airframe of a gyroplane rather than beingobtained through the rotor system. As a result, differentforces act on a gyroplane in flight than on a helicopter.Engine torque, for example, tends to roll the fuselagein the direction opposite propeller rotation, causing itto be deflected a few degrees out of the vertical plane.[Figure 16-8] This slight “out of vertical” condition isusually negligible and not considered relevant for mostflight operations.

STABILITYStability is designed into aircraft to reduce pilot work-load and increase safety. A stable aircraft, such as a typ-ical general aviation training airplane, requires lessattention from the pilot to maintain the desired flightattitude, and will even correct itself if disturbed by agust of wind or other outside forces. Conversely, anunstable aircraft requires constant attention to maintaincontrol of the aircraft.

Reactive Torque on Fuselage

Torque Applied to Propeller

Figure 16-8. Engine torque applied to the propeller has anequal and opposite reaction on the fuselage, deflecting it afew degrees out of the vertical plane in flight.

Pendular Action—The lateral orlongitudinal oscillation of the fuse-lage due to it being suspendedfrom the rotor system. It is similarto the action of a pendulum.Pendular action is further dis-cussed in Chapter 3—Aerodynamics of Flight.

There are several factors that contribute to the stabilityof a gyroplane. One is the location of the horizontal stabilizer. Another is the location of the fuselage dragin relation to the center of gravity. A third is the inertia moment around the pitch axis, while a fourth isthe relation of the propeller thrust line to the verticallocation of the center of gravity (CG). However, theone that is probably the most critical is the relation ofthe rotor force line to the horizontal location of the center of gravity.

HORIZONTAL STABILIZERA horizontal stabilizer helps in longitudinal stability,with its efficiency greater the further it is from the center of gravity. It is also more efficient at higher airspeeds because lift is proportional to the square ofthe airspeed. Since the speed of a gyroplane is not veryhigh, manufacturers can achieve the desired stabilityby varying the size of the horizontal stabilizer, chang-ing the distance it is from the center of gravity, or byplacing it in the propeller slipstream.

FUSELAGE DRAG(CENTER OF PRESSURE)If the location, where the fuselage drag or center ofpressure forces are concentrated, is behind the CG,the gyroplane is considered more stable. This is espe-cially true of yaw stability around the vertical axis.However, to achieve this condition, there must be asufficient vertical tail surface. In addition, the gyro-plane needs to have a balanced longitudinal center ofpressure so there is sufficient cyclic movement toprevent the nose from tucking under or lifting, aspressure builds on the frontal area of the gyroplane asairspeed increases.

PITCH INERTIAWithout changing the overall weight and center ofgravity of a gyroplane, the further weights are placedfrom the CG, the more stable the gyroplane. For exam-ple, if the pilot's seat could be moved forward from theCG, and the engine moved aft an amount, which keepsthe center of gravity in the same location, the gyroplanebecomes more stable. A tightrope walker applies thissame principle when he uses a long pole to balancehimself.

PROPELLER THRUST LINEConsidering just the propeller thrust line by itself, if thethrust line is above the center of gravity, the gyroplanehas a tendency to pitch nose down when power isapplied, and to pitch nose up when power is removed.The opposite is true when the propeller thrust line isbelow the CG. If the thrust line goes through the CG or

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nearly so there is no tendency for the nose to pitch upor down. [Figure 16-9]

ROTOR FORCEBecause some gyroplanes do not have horizontal stabi-lizers, and the propeller thrust lines are different, gyro-plane manufacturers can achieve the desired stabilityby placing the center of gravity in front of or behind therotor force line. [Figure 16-10]

Suppose the CG is located behind the rotor force line inforward flight. If a gust of wind increases the angle ofattack, rotor force increases. There is also an increasein the difference between the lift produced on theadvancing and retreating blades. This increases theflapping angle and causes the rotor to pitch up. Thispitching action increases the moment around the centerof gravity, which leads to a greater increase in the angleof attack. The result is an unstable condition.

If the CG is in front of the rotor force line, a gust ofwind, which increases the angle of attack, causes therotor disc to react the same way, but now the increasein rotor force and blade flapping decreases themoment. This tends to decrease the angle of attack, andcreates a stable condition.

TRIMMED CONDITIONAs was stated earlier, manufacturers use a combinationof the various stability factors to achieve a trimmedgyroplane. For example, if you have a gyroplane wherethe CG is below the propeller thrust line, the propellerthrust gives your aircraft a nose down pitching momentwhen power is applied. To compensate for this pitchingmoment, the CG, on this type of gyroplane, is usuallylocated behind the rotor force line. This location pro-duces a nose up pitching moment.

Conversely, if the CG is above the propeller thrust line,the CG is usually located ahead of the rotor force line.Of course, the location of fuselage drag, the pitch iner-tia, and the addition of a horizontal stabilizer can alterwhere the center of gravity is placed.

Propeller Thrust

Propeller Thrust

Center of Gravity Center of Gravity

High ProfileLow Profile

Rot

orF

orce

Rot

orF

orce

Figure 16-9. A gyroplane which has the propeller thrust line above the center of gravity is often referred to as a low profile gyro-plane. One that has the propeller thrust line below or at the CG is considered a high profile gyroplane.

Figure 16-10. If the CG is located in front of the rotor force line, the gyroplane is more stable than if the CG is located behind therotor force line.

Blade Flapping—The upward or downward movement of the rotor-blades during rotation.

17-1

Due to rudimentary flight control systems, early gyroplanessuffered from limited maneuverability. As technologyimproved, greater control of the rotor system and moreeffective control surfaces were developed. The moderngyroplane, while continuing to maintain an element ofsimplicity, now enjoys a high degree of maneuver-ability as a result of these improvements.

CYCLIC CONTROLThe cyclic control provides the means whereby you areable to tilt the rotor system to provide the desiredresults. Tilting the rotor system provides all control forclimbing, descending, and banking the gyroplane. Themost common method to transfer stick movement tothe rotor head is through push-pull tubes or flex cables.[Figure 17-1] Some gyroplanes use a direct overheadstick attachment rather than a cyclic, where a rigid con-trol is attached to the rotor hub and descends over andin front of the pilot. [Figure 17-2] Because of thenature of the direct attachment, control inputs with thissystem are reversed from those used with a cyclic.Pushing forward on the control causes the rotor disc totilt back and the gyroplane to climb, pulling back onthe control initiates a descent. Bank commands arereversed in the same way.

THROTTLEThe throttle is conventional to most powerplants, andprovides the means for you to increase or decreaseengine power and thus, thrust. Depending on how

the control is designed, control movement may ormay not be proportional to engine power. With manygyroplane throttles, 50 percent of the control travelmay equate to 80 or 90 percent of available power.This varying degree of sensitivity makes it necessary

Figure 17-1. A common method of transferring cyclic control inputs to the rotor head is through the use of push-pull tubes,located outboard of the rotor mast pictured on the right.

Figure 17-2. The direct overhead stick attachment has beenused for control of the rotor disc on some gyroplanes.

17-2

for you to become familiar with the unique throttle characteristics and engine responses for a particulargyroplane.

RUDDERThe rudder is operated by foot pedals in the cockpit and provides a means to control yaw movement of theaircraft. [Figure 17-3] On a gyroplane, this control isachieved in a manner more similar to the rudder of anairplane than to the antitorque pedals of a helicopter.The rudder is used to maintain coordinated flight, andat times may also require inputs to compensate for propeller torque. Rudder sensitivity and effectivenessare directly proportional to the velocity of airflow overthe rudder surface. Consequently, many gyroplane rudders are located in the propeller slipstream and provide excellent control while the engine is developingthrust. This type of rudder configuration, however, isless effective and requires greater deflection when theengine is idled or stopped.

HORIZONTAL TAIL SURFACESThe horizontal tail surfaces on most gyroplanes are not controllable by the pilot. These fixed surfaces, or

stabilizers, are incorporated into gyroplane designs toincrease the pitch stability of the aircraft. Some gyro-planes use very little, if any, horizontal surface. Thistranslates into less stability, but a higher degree ofmaneuverability. When used, a moveable horizontalsurface, or elevator, adds additional pitch control of theaircraft. On early tractor configured gyroplanes, theelevator served an additional function of deflecting thepropeller slipstream up and through the rotor to assistin prerotation.

COLLECTIVE CONTROLThe collective control provides a means to vary therotor blade pitch of all the blades at the same time, andis available only on more advanced gyroplanes. Whenincorporated into the rotor head design, the collectiveallows jump takeoffs when the blade inertia is suffi-cient. Also, control of in-flight rotor r.p.m. is availableto enhance cruise and landing performance. A simpletwo position collective does not allow unlimited controlof blade pitch, but instead has one position for prerotationand another position for flight. This is a performancecompromise but reduces pilot workload by simplifyingcontrol of the rotor system.

Figure 17-3. Foot pedals provide rudder control and operation is similar to that of an airplane.

18-1

rotating portion of the head to the non-rotating torquetube. The torque tube is mounted to the airframethrough attachments allowing both lateral and longitu-dinal movement. This allows the movement throughwhich control is achieved.

FULLY ARTICULATED ROTOR SYSTEM The fully articulated rotor system is found on somegyroplanes. As with helicopter-type rotor systems, thearticulated rotor system allows the manipulation of

Coning Angle—An angulardeflection of the rotor bladesupward from the rotor hub.

Undersling—A design character-istic that prevents the distancebetween the rotor mast axis andthe center of mass of each rotorblade from changing as theblades teeter. This precludesCoriolis Effect from acting on thespeed of the rotor system.Undersling is further explainedin Chapter 3—Aerodynamics ofFlight, Coriolis Effect (Law ofConservation of AngularMomentum).

Gyroplanes are available in a wide variety of designsthat range from amateur built to FAA-certificated air-craft. Similarly, the complexity of the systems inte-grated in gyroplane design cover a broad range. Toensure the airworthiness of your aircraft, it is importantthat you thoroughly understand the design and opera-tion of each system employed by your machine.

PROPULSION SYSTEMSMost of the gyroplanes flying today use a reciprocatingengine mounted in a pusher configuration that driveseither a fixed or constant speed propeller. The enginesused in amateur-built gyroplanes are normally provenpowerplants adapted from automotive or other uses.Some amateur-built gyroplanes use FAA-certificated air-craft engines and propellers. Auto engines, along withsome of the other powerplants adapted to gyroplanes,operate at a high r.p.m., which requires the use of a reduc-tion unit to lower the output to efficient propeller speeds.

Early autogyros used existing aircraft engines, whichdrove a propeller in the tractor configuration. Severalamateur-built gyroplanes still use this propulsion con-figuration, and may utilize a certificated or an uncer-tificated engine. Although not in use today, turbopropand pure jet engines could also be used for the propul-sion of a gyroplane.

ROTOR SYSTEMSSEMIRIGID ROTOR SYSTEMAny rotor system capable of autorotation may be utilizedin a gyroplane. Because of its simplicity, the most widelyused system is the semirigid, teeter-head system. Thissystem is found in most amateur-built gyroplanes.[Figure 18-1] In this system, the rotor head is mountedon a spindle, which may be tilted for control. The rotorblades are attached to a hub bar that may or may nothave adjustments for varying the blade pitch. A coningangle, determined by projections of blade weight,rotor speed, and load to be carried, is built into the hubbar. This minimizes hub bar bending moments andeliminates the need for a coning hinge, which is usedin more complex rotor systems. A tower block pro-vides the undersling and attachment to the rotor headby the teeter bolt. The rotor head is comprised of abearing block in which the bearing is mounted andonto which the tower plates are attached. The spindle(commonly, a vertically oriented bolt) attaches the

Figure 18-1. The semirigid, teeter-head system is found onmost amateur-built gyroplanes. The rotor hub bar and bladesare permitted to tilt by the teeter bolt.

Tower Plates

Hub Bar

Tower Block

Bearing Block

Teeter Bolt

Spindle Bolt

Torque Tube

Fore / Aft Pivot Bolt

Lateral Pivot Bolt

18-2

rotor blade pitch while in flight. This system is signifi-cantly more complicated than the teeter-head, as itrequires hinges that allow each rotor blade to flap,feather, and lead or lag independently. [Figure 18-2]When used, the fully articulated rotor system of a gyro-plane is very similar to those used on helicopters, whichis explained in depth in Chapter 5—Helicopter Systems,Main Rotor Systems. One major advantage of using afully articulated rotor in gyroplane design is that it usu-ally allows jump takeoff capability. Rotor characteristicsrequired for a successful jump takeoff must include amethod of collective pitch change, a blade with sufficientinertia, and a prerotation mechanism capable of approxi-mately 150 percent of rotor flight r.p.m.

Incorporating rotor blades with high inertia potential isdesirable in helicopter design and is essential for jumptakeoff gyroplanes. A rotor hub design allowing therotor speed to exceed normal flight r.p.m. by over 50 percent is not found in helicopters, and predicates arotor head design particular to the jump takeoff gyroplane, yet very similar to that of the helicopter.

PREROTATORPrior to takeoff, the gyroplane rotor must first achievea rotor speed sufficient to create the necessary lift.This is accomplished on very basic gyroplanes by ini-tially spinning the blades by hand. The aircraft is thentaxied with the rotor disc tilted aft, allowing airflowthrough the system to accelerate it to flight r.p.m.More advanced gyroplanes use a prerotator, whichprovides a mechanical means to spin the rotor. Manyprerotators are capable of only achieving a portion ofthe speed necessary for flight; the remainder isgained by taxiing or during the takeoff roll. Becauseof the wide variety of prerotation systems available,you need to become thoroughly familiar with thecharacteristics and techniques associated with yourparticular system.

MECHANICAL PREROTATORMechanical prerotators typically have clutches or beltsfor engagement, a drive train, and may use a transmis-sion to transfer engine power to the rotor. Frictiondrives and flex cables are used in conjunction with anautomotive type bendix and ring gear on many gyro-planes. [Figure 18-3]

The mechanical prerotator used on jump takeoff gyro-planes may be regarded as being similar to the helicoptermain rotor drive train, but only operates while the air-craft is firmly on the ground. Gyroplanes do not have anantitorque device like a helicopter, and ground contact isnecessary to counteract the torque forces generated bythe prerotation system. If jump takeoff capability isdesigned into a gyroplane, rotor r.p.m. prior to liftoffmust be such that rotor energy will support the air-craft through the acceleration phase of takeoff. Thiscombination of rotor system and prerotator utilizesthe transmission only while the aircraft is on theground, allowing the transmission to be disconnectedfrom both the rotor and the engine while in normalflight.

HYDRAULIC PREROTATORThe hydraulic prerotator found on gyroplanes usesengine power to drive a hydraulic pump, which in turndrives a hydraulic motor attached to an automotive typebendix and ring gear. [Figure 18-4] This system alsorequires that some type of clutch and pressure regula-tion be incorporated into the design.

Figure 18-2. The fully articulated rotor system enables thepilot to effect changes in pitch to the rotor blades, which isnecessary for jump takeoff capability.

Figure 18-3. The mechanical prerotator used by many gyro-planes uses a friction drive at the propeller hub, and a flexi-ble cable that runs from the propeller hub to the rotor mast.When engaged, the bendix spins the ring gear located on therotor hub.

18-3

ELECTRIC PREROTATORThe electric prerotator found on gyroplanes uses anautomotive type starter with a bendix and ring gearmounted at the rotor head to impart torque to the rotorsystem. [Figure 18-5] This system has the advantage ofsimplicity and ease of operation, but is dependent onhaving electrical power available. Using a “soft start”device can alleviate the problems associated with thehigh starting torque initially required to get the rotorsystem turning. This device delivers electrical pulses tothe starter for approximately 10 seconds before con-necting uninterrupted voltage.

TIP JETSJets located at the rotor blade tips have been used in sev-eral applications for prerotation, as well as for hoverflight. This system has no requirement for a transmissionor clutches. It also has the advantage of not impartingtorque to the airframe, allowing the rotor to be poweredin flight to give increased climb rates and even the abilityto hover. The major disadvantage is the noise generatedby the jets. Fortunately, tip jets may be shut down whileoperating in the autorotative gyroplane mode.

INSTRUMENTATIONThe instrumentation required for flight is generallyrelated to the complexity of the gyroplane. Some gyro-planes using air-cooled and fuel/oil-lubricated enginesmay have limited instrumentation.

ENGINE INSTRUMENTSAll but the most basic engines require monitoringinstrumentation for safe operation. Coolant tempera-ture, cylinder head temperatures, oil temperature, oilpressure, carburetor air temperature, and exhaust gastemperature are all direct indications of engine opera-tion and may be displayed. Engine power is normallyindicated by engine r.p.m., or by manifold pressure ongyroplanes with a constant speed propeller.

ROTOR TACHOMETERMost gyroplanes are equipped with a rotor r.p.m. indica-tor. Because the pilot does not normally have direct control of rotor r.p.m. in flight, this instrument is mostuseful on the takeoff roll to determine when there is suf-ficient rotor speed for liftoff. On gyroplanes notequipped with a rotor tachometer, additional pilotingskills are required to sense rotor r.p.m. prior to takeoff.

Figure 18-4. This prerotator uses belts at the propeller hub to drive a hydraulic pump, which drives a hydraulic motor on therotor mast.

Figure 18-5. The electric prerotator is simple and easy to use,but requires the availability of electrical power.

18-4

Certain gyroplane maneuvers require you to know pre-cisely the speed of the rotor system. Performing a jumptakeoff in a gyroplane with collective control is oneexample, as sufficient rotor energy must be availablefor the successful outcome of the maneuver. Whenvariable collective and a rotor tachometer are used,more efficient rotor operation may be accomplished byusing the lowest practical rotor r.p.m. [Figure 18-6]

SLIP/SKID INDICATORA yaw string attached to the nose of the aircraft and aconventional inclinometer are often used in gyroplanesto assist in maintaining coordinated flight. [Figure 18-7]

AIRSPEED INDICATORAirspeed knowledge is essential and is most easilyobtained by an airspeed indicator that is designed foraccuracy at low airspeeds. Wind speed indicatorshave been adapted to many gyroplanes. When no air-

speed indicator is used, as in some very basic amateur-built machines, you must have a very acutesense of “q” (impact air pressure against your body).

ALTIMETERFor the average pilot, it becomes increasingly difficultto judge altitude accurately when more than severalhundred feet above the ground. A conventional altime-ter may be used to provide an altitude reference whenflying at higher altitudes where human perceptiondegrades.

IFR FLIGHT INSTRUMENTATIONGyroplane flight into instrument meteorological condi-tions requires adequate flight instrumentation and navi-gational systems, just as in any aircraft. Very fewgyroplanes have been equipped for this type of operation.The majority of gyroplanes do not meet the stabilityrequirements for single-pilot IFR flight. As larger andmore advanced gyroplanes are developed, issues of IFRflight in these aircraft will have to be addressed.

GROUND HANDLINGThe gyroplane is capable of ground taxiing in a mannersimilar to that of an airplane. A steerable nose wheel,which may be combined with independent main wheelbrakes, provides the most common method of control.[Figure 18-8] The use of independent main wheelbrakes allows differential braking, or applying morebraking to one wheel than the other to achieve tightradius turns. On some gyroplanes, the steerable nosewheel is equipped with a foot-operated brake ratherthan using main wheel brakes. One limitation of thissystem is that the nose wheel normally supports only afraction of the weight of the gyroplane, which greatlyreduces braking effectiveness. Another drawback is the

Figure 18-6. A rotor tachometer can be very useful to deter-mine when rotor r.p.m. is sufficient for takeoff.

Figure 18-7. A string simply tied near the nose of the gyro-plane that can be viewed from the cockpit is often used toindicate rotation about the yaw axis. An inclinometer mayalso be used.

Figure 18-8. Depending on design, main wheel brakes can beoperated either independently or collectively. They are con-siderably more effective than nose wheel brakes.

18-5

inability to use differential braking, which increasesthe radius of turns.

The rotor blades demand special consideration duringground handling, as turning rotor blades can be a haz-ard to those nearby. Many gyroplanes have a rotor

brake that may be used to slow the rotor after landing,or to secure the blades while parked. A parked gyro-plane should never be left with unsecured blades,because even a slight change in wind could cause theblades to turn or flap.

18-6

19-1

As with most certificated aircraft manufactured afterMarch 1979, FAA-certificated gyroplanes are requiredto have an approved flight manual. The flight manualdescribes procedures and limitations that must beadhered to when operating the aircraft. Specificationfor Pilot’s Operating Handbook, published by theGeneral Aviation Manufacturers Association (GAMA),provides a recommended format that more recent gyro-plane flight manuals follow. [Figure 19-1]

This format is the same as that used by helicopters,which is explained in depth in Chapter 6—RotorcraftFlight Manual (Helicopter).

Amateur-built gyroplanes may have operating limita-tions but are not normally required to have an approvedflight manual. One exception is an exemption grantedby the FAA that allows the commercial use of two-place, amateur-built gyroplanes for instructionalpurposes. One of the conditions of this exemption is tohave an approved flight manual for the aircraft. Thismanual is to be used for training purposes, and must becarried in the gyroplane at all times.

USING THE FLIGHT MANUALThe flight manual is required to be on board the aircraftto guarantee that the information contained therein isreadily available. For the information to be of value,you must be thoroughly familiar with the manual andbe able to read and properly interpret the various chartsand tables.

WEIGHT AND BALANCE SECTIONThe weight and balance section of the flight manualcontains information essential to the safe operation ofthe gyroplane. Careful consideration must be given tothe weight of the passengers, baggage, and fuel prior toeach flight. In conducting weight and balance compu-tations, many of the terms and procedures are similar tothose used in helicopters. These are further explainedin Chapter 7—Weight and Balance. In any aircraft,failure to adhere to the weight and balance limita-tions prescribed by the manufacturer can beextremely hazardous.

SAMPLE PROBLEMAs an example of a weight and balance computation,assume a sightseeing flight in a two-seat, tandem-con-figured gyroplane with two people aboard. The pilot,seated in the front, weighs 175 pounds while the rearseat passenger weighs 160 pounds. For the purposes ofthis example, there will be no baggage carried. Thebasic empty weight of the aircraft is 1,315 pounds witha moment, divided by 1,000, of 153.9 pound-inches.

ROTORCRAFT FLIGHT MANUAL

GENERAL—Presents basic information, such as loading, handling, and preflight of the gyroplane. Also includes definitions, abbreviations, symbology, and terminology explanations. LIMITATIONS—Includes operating limitations, instrument markings, color coding, and basic placards necessary for the safe operation of the gyroplane. EMERGENCY PROCEDURES—Provides checklists followed by amplified procedures for coping with various types of emergencies or critical situations. Related recommended airspeeds are also included. At the manufacturer's option, a section of abnormal procedures may be included to describe recommendations for handling equipment malfunctions or other abnormalities that are not of an emergency nature. NORMAL PROCEDURES—Includes checklists followed by amplified procedures for conducting normal operations. Related recommended airspeeds are also provided. PERFORMANCE—Gives performance information appropriate to the gyroplane, plus optional information presented in the most likely order for use in flight. WEIGHT AND BALANCE—Includes weighing procedures, weight and balance records, computation instructions, and the equipment list. AIRCRAFT AND SYSTEMS DESCRIPTION—Describes the gyroplane and its systems in a format considered by the manufacturer to be most informative. HANDLING, SERVICE, AND MAINTENANCE—Includes information on gyroplane inspection periods, preventative maintenance that can be performed by the pilot, ground handling procedures, servicing, cleaning, and care instructions. SUPPLEMENTS—Contains information necessary to safely and efficiently operate the gyroplane's various optional systems and equipment. SAFETY AND OPERATIONAL TIPS—Includes optional information from the manufacturer of a general nature addressing safety practices and procedures.

Figure 19-1. The FAA-approved flight manual may contain asmany as ten sections, as well as an optional alphabeticalindex.

19-2

Using the loading graph [Figure 19-2], themoment/1000 of the pilot is found to be 9.1 pound-inches, and the passenger has a moment/1000 of 13.4pound-inches.

Adding these figures, the total weight of the aircraft forthis flight (without fuel) is determined to be 1,650pounds with a moment/1000 of 176.4 pound-inches.[Figure 19-3]

The maximum gross weight for the sample aircraft is1,800 pounds, which allows up to 150 pounds to be car-ried in fuel. For this flight, 18 gallons of fuel is deemedsufficient. Allowing six pounds per gallon of fuel, thefuel weight on the aircraft totals 108 pounds. Referringagain to the loading graph [Figure 19-2], 108 pounds offuel would have a moment/1000 of 11.9 pound-inches.This is added to the previous totals to obtain the totalaircraft weight of 1,758 pounds and a moment/1000 of188.3. Locating this point on the center of gravity enve-lope chart [Figure 19-4], shows that the loading iswithin the prescribed weight and balance limits.

PERFORMANCE SECTIONThe performance section of the flight manual containsdata derived from actual flight testing of the aircraft.Because the actual performance may differ, it is pru-dent to maintain a margin of safety when planningoperations using this data.

SAMPLE PROBLEMFor this example, a gyroplane at its maximum grossweight (1,800 lbs.) needs to perform a short field take-off due to obstructions in the takeoff path. Presentweather conditions are standard temperature at a pres-sure altitude of 2,000 feet, and the wind is calm.Referring to the appropriate performance chart [Figure19-5], the takeoff distance to clear a 50-foot obstacle isdetermined by entering the chart from the left at thepressure altitude of 2,000 feet. You then proceed hori-zontally to the right until intersecting the appropriatetemperature reference line, which in this case is thedashed standard temperature line. From this point,descend vertically to find the total takeoff distance toclear a 50-foot obstacle. For the conditions given, thisparticular gyroplane would require a distance of 940feet for ground roll and the distance needed to climb 50feet above the surface. Notice that the data presented inthis chart is predicated on certain conditions, such as arunning takeoff to 30 m.p.h., a 50 m.p.h. climb speed, a

Weight Moment (pounds) (lb.-in./1,000)

Basic Empty Weight

Pilot

Passenger

Baggage

Total Aircraft (Less Fuel)

1,315

175

160

0

1,650

153.9

9.1

13.4

0

176.4

Max Gross Weight = 1,800 lbs.

Figure 19-3. Loading of the sample aircraft, less fuel.

CENTER OF GRAVITY ENVELOPE

Gross Moment in Thousands of LBS-IN.

Gro

ssW

eigh

tin

Pou

nds

(x10

0)

160 180 190 200170

15

16

17

18

1. Total Aircraft Weight (Less Fuel) ...............................

3. Fuel...........................................

TOTALS

Weight (lbs.)

Moment (lb.-ins. /1,000)

176.41,650

11.9108

188.31,758

AftForw

ard

Figure 19-4. Center of gravity envelope chart.

0 2 4 6 8 10 12 14 16 18 20

1

2

3

Load

Wei

ghti

nP

ound

s(x

100)

Load Moment in Thousands of LBS - IN

LOADING GRAPH

A

B

C

D

A = PilotB = Passenger

C = FuelD = Baggage

Figure 19-2. A loading graph is used to determine the loadmoment for weights at various stations.

19-3

rotor prerotation speed of 370 r.p.m., and no wind.Variations from these conditions alter performance,possibly to the point of jeopardizing the successful out-come of the maneuver.

HEIGHT/VELOCITY DIAGRAMLike helicopters, gyroplanes have a height/velocity diagram that defines what speed and altitude combina-tions allow for a safe landing in the event of an enginefailure. [Figure 19-6]

During an engine-out landing, the cyclic flare is used toarrest the vertical velocity of the aircraft and most of theforward velocity. On gyroplanes with a manual collec-tive control, increasing blade pitch just prior to touch-down can further reduce ground roll. Typically, agyroplane has a lower rotor disc loading than a helicop-ter, which provides a slower rate of descent in autorota-tion. The power required to turn the main transmission,tail rotor transmission, and tail rotor also add to thehigher descent rate of a helicopter in autorotation ascompared with that of a gyroplane.

EMERGENCY SECTIONBecause in-flight emergencies may not allow enoughtime to reference the flight manual, the emergency sec-tion should be reviewed periodically to maintainfamiliarity with these procedures. Many aircraft alsouse placards and instrument markings in the cockpit,

which provide important information that may not becommitted to memory.

Running Takeoff to 30 MPH & Climb out at 50 MPH CAS Weight 1800 LBS Rotor Prerotated to 370 RPM

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Total Takeoff Distance to Clear 50 FT Obstacle in Feet (x 100)

Pre

ssur

eA

ltitu

dein

Fee

t(x

1000

)

1

2

3

4

5

6

7

8

TOTAL TAKEOFF DISTANCE TO CLEAR 50 FT. OBSTACLE

Zero Wind

0° F20° F

Std. Temp.40° F60° F80° F

100° F

Figure 19-5. Takeoff performance chart.

HEIGHT vs. VELOCITY FOR SAFE LANDING

Avoid Continuous Operation In Shaded Area.

0 20 40 60 80 100

Indicated Airspeed In MPH

Hei

ghtA

bove

Run

way

InF

eet

400

300

200

100

0

Figure 19-6. Operations within the shaded area of aheight/velocity diagram may not allow for a safe landing andare to be avoided.

19-4

HANG TESTThe proper weight and balance of a gyroplane withouta flight manual is normally determined by conductinga hang test of the aircraft. This is achieved by remov-ing the rotor blades and suspending the aircraft by itsteeter bolt, free from contact with the ground. A meas-urement is then taken, either at the keel or the rotormast, to determine how many degrees from level the

gyroplane hangs. This number must be within therange specified by the manufacturer. For the test toreflect the true balance of the aircraft, it is importantthat it be conducted using the actual weight of the pilotand all gear normally carried in flight. Additionally,the measurement should be taken both with the fueltank full and with it empty to ensure that fuel burndoes not affect the loading.

20-1

The diversity of gyroplane designs available todayyields a wide variety of capability and performance.For safe operation, you must be thoroughly familiarwith the procedures and limitations for your particularaircraft along with other factors that may affect thesafety of your flight.

PREFLIGHTAs pilot in command, you are the final authority indetermining the airworthiness of your aircraft.Adherence to a preflight checklist greatly enhancesyour ability to evaluate the fitness of your gyroplane byensuring that a complete and methodical inspection ofall components is performed. [Figure 20-1] For aircraftwithout a formal checklist, it is prudent to create onethat is specific to the aircraft to be sure that importantitems are not overlooked. To determine the status ofrequired inspections, a preflight review of the aircraftrecords is also necessary.

COCKPIT MANAGEMENTAs in larger aircraft, cockpit management is an impor-tant skill necessary for the safe operation of a gyroplane. Intrinsic to these typically small aircraft is alimited amount of space that must be utilized to its

potential. The placement and accessibility of charts,writing materials, and other necessary items must becarefully considered. Gyroplanes with open cockpitsadd the challenge of coping with wind, which furtherincreases the need for creative and resourceful cockpitmanagement for optimum efficiency.

ENGINE STARTINGThe dissimilarity between the various types of enginesused for gyroplane propulsion necessitates the use ofan engine start checklist. Again, when a checklist is notprovided, it is advisable to create one for the safety ofyourself and others, and to prevent inadvertent damageto the engine or propeller. Being inherently dangerous,the propeller demands special attention during enginestarting procedures. Always ensure that the propellerarea is clear prior to starting. In addition to providingan added degree of safety, being thoroughly familiarwith engine starting procedures and characteristics canalso be very helpful in starting an engine under variousweather conditions.

TAXIINGThe ability of the gyroplane to be taxied greatlyenhances its utility. However, a gyroplane should notbe taxied in close proximity to people or obstructionswhile the rotor is turning. In addition, taxi speed shouldbe limited to no faster than a brisk walk in ideal condi-tions, and adjusted appropriately according to the circumstances.

BLADE FLAPOn a gyroplane with a semi-rigid, teeter-head rotor sys-tem, blade flap may develop if too much airflow passesthrough the rotor system while it is operating at lowr.p.m. This is most often the result of taxiing too fastfor a given rotor speed. Unequal lift acting on theadvancing and retreating blades can cause the blades toteeter to the maximum allowed by the rotor headdesign. The blades then hit the teeter stops, creating avibration that may be felt in the cyclic control. The fre-quency of the vibration corresponds to the speed of therotor, with the blades hitting the stops twice duringeach revolution. If the flapping is not controlled, thesituation can grow worse as the blades begin to flex and

Figure 20-1. A checklist is extremely useful in conducting athorough preflight inspection.

20-2

bend. Because the system is operating at low r.p.m.,there is not enough centrifugal force acting on theblades to keep them rigid. The shock of hitting theteeter stops combined with uneven lift along the lengthof the blade causes an undulation to begin, which canincrease in severity if allowed to progress. In extremecases, a rotor blade may strike the ground or propeller.[Figure 20-2]

To avoid the onset of blade flap, always taxi the gyro-plane at slow speeds when the rotor system is at lowr.p.m. Consideration must also be given to wind speedand direction. If taxiing into a 10-knot headwind, forexample, the airflow through the rotor will be 10 knotsfaster than the forward speed of the gyroplane, so thetaxi speed should be adjusted accordingly. When pre-rotating the rotor by taxiing with the rotor disc tiltedaft, allow the rotor to accelerate slowly and smoothly.In the event blade flap is encountered, apply forwardcyclic to reduce the rotor disc angle and slow the gyro-plane by reducing throttle and applying the brakes, ifneeded. [Figure 20-3]

BEFORE TAKEOFFFor the amateur-built gyroplane using single ignitionand a fixed trim system, the before takeoff check isquite simple. The engine should be at normal operatingtemperature, and the area must be clear for prerotation.Certificated gyroplanes using conventional aircraftengines have a checklist that includes items specific tothe powerplant. These normally include, but are notlimited to, checks for magneto drop, carburetor heat,and, if a constant speed propeller is installed, that it becycled for proper operation.

Following the engine run-up is the procedure foraccomplishing prerotation. This should be reviewedand committed to memory, as it typically requires bothhands to perform.

PREROTATIONPrerotation of the rotor can take many forms in a gyroplane. The most basic method is to turn the rotorblades by hand. On a typical gyroplane with a counter-clockwise rotating rotor, prerotation by hand is done onthe right side of the rotor disk. This allows body movement to be directed away from the propeller tominimize the risk of injury. Other methods of prerota-tion include using mechanical, electrical, or hydraulicmeans for the initial blade spin-up. Many of these systems can achieve only a portion of the rotor speedthat is necessary for takeoff. After the prerotator is disengaged, taxi the gyroplane with the rotor disk tiltedaft to allow airflow through the rotor. This increasesrotor speed to flight r.p.m. In windy conditions, facingthe gyroplane into the wind during prerotation assistsin achieving the highest possible rotor speed from theprerotator. A factor often overlooked that can nega-tively affect the prerotation speed is the cleanliness ofthe rotor blades. For maximum efficiency, it is recom-mended that the rotor blades be cleaned periodically.By obtaining the maximum possible rotor speedthrough the use of proper prerotation techniques, you

Figure 20-2. Taxiing too fast or gusting winds can causeblade flap in a slow turning rotor. If not controlled, a rotorblade may strike the ground.

Rotor Ground Clearance

Airflow

Rotor Ground Clearance

Airflow

Figure 20-3. Decreasing the rotor disc angle of attack with forward cyclic can reduce the excessive amount of airflow causingthe blade flap. This also allows greater clearance between the rotor blades and the surface behind the gyroplane, minimizingthe chances of a blade striking the ground.

20-3

minimize the length of the ground roll that is requiredto get the gyroplane airborne.

The prerotators on certificated gyroplanes remove thepossibility of blade flap during prerotation. Before theclutch can be engaged, the pitch must be removed fromthe blades. The rotor is then prerotated with a 0° angleof attack on the blades, which prevents lift from beingproduced and precludes the possibility of flapping.When the desired rotor speed is achieved, blade pitch isincreased for takeoff.

TAKEOFFTakeoffs are classified according to the takeoff surface,obstructions, and atmospheric conditions. Each type oftakeoff assumes that certain conditions exist. Whenconditions dictate, a combination of takeoff techniquescan be used. Two important speeds used for takeoff andinitial climbout are VX and VY. VX is defined as thespeed that provides the best angle of climb, and willyield the maximum altitude gain over a given distance.This speed is normally used when obstacles on theground are a factor. Maintaining VY speed ensures theaircraft will climb at its maximum rate, providing themost altitude gain for a given period of time. [Figure 20-4] Prior to any takeoff or maneuver, youshould ensure that the area is clear of other traffic.

NORMAL TAKEOFFThe normal takeoff assumes that a prepared surface ofadequate length is available and that there are no highobstructions to be cleared within the takeoff path. Thenormal takeoff for most amateur-built gyroplanes isaccomplished by prerotating to sufficient rotor r.p.m. toprevent blade flapping and tilting the rotor back withcyclic control. Using a speed of 20 to 30 m.p.h., allowthe rotor to accelerate and begin producing lift. As liftincreases, move the cyclic forward to decrease the pitchangle on the rotor disc. When appreciable lift is beingproduced, the nose of the aircraft rises, and you can feelan increase in drag. Using coordinated throttle andflight control inputs, balance the gyroplane on the maingear without the nose wheel or tail wheel in contactwith the surface. At this point, smoothly increase powerto full thrust and hold the nose at takeoff attitude withcyclic pressure. The gyroplane will lift off at or nearthe minimum power required speed for the aircraft. VXshould be used for the initial climb, then VY for theremainder of the climb phase.

A normal takeoff for certificated gyroplanes is accom-plished by prerotating to a rotor r.p.m. slightly abovethat required for flight and disengaging the rotor drive.The brakes are then released and full power is applied.Lift off will not occur until the blade pitch is increasedto the normal in-flight setting and the rotor disk tilted

Best Rate of Climb (V Y

)

BestAngle

of Climb (V X

)

30

Figure 20-4. Best angle-of-climb (VX) speed is used when obstacles are a factor. VY provides the most altitude gain for a givenamount of time.

20-4

power applied as soon as appreciable lift is felt. VXclimb speed should be maintained until the obstructionis cleared. Familiarity with the rotor acceleration characteristics and proper technique are essential foroptimum short-field performance.

If the prerotator is capable of spinning the rotor inexcess of normal flight r.p.m., the stored energy may beused to enhance short-field performance. Once maxi-mum rotor r.p.m. is attained, disengage the rotor drive,release the brakes, and apply power. As airspeed androtor r.p.m. increase, apply additional power until fullpower is achieved. While remaining on the ground,accelerate the gyroplane to a speed just prior to VX. Atthat point, tilt the disk aft and increase the blade pitchto the normal in-flight setting. The climb should be at aspeed just under VX until rotor r.p.m. has dropped tonormal flight r.p.m. or the obstruction has been cleared.When the obstruction is no longer a factor, increase theairspeed to VY.

COMMON ERRORS

1. Failure to position gyroplane for maximum utilization of available takeoff area.

2. Failure to check rotor for proper operation, track,and r.p.m. prior to takeoff.

3. Improper initial positioning of flight controls.

4. Improper application of power.

5. Improper use of brakes.

6. Poor directional control.

7. Failure to lift off at proper airspeed.

8. Failure to establish and maintain proper climbattitude and airspeed.

9. Drifting from the desired ground track during theclimb.

HIGH-ALTITUDE TAKEOFFA high-altitude takeoff is conducted in a manner verysimilar to that of the short-field takeoff, which achievesmaximum performance from the aircraft during eachphase of the maneuver. One important consideration isthat at higher altitudes, rotor r.p.m. is higher for a givenblade pitch angle. This higher speed is a result of thin-ner air, and is necessary to produce the same amount oflift. The inertia of the excess rotor speed should not beused in an attempt to enhance climb performance.Another important consideration is the effect of alti-tude on engine performance. As altitude increases, theamount of oxygen available for combustion decreases.In normally aspirated engines, it may be necessary to

aft. This is normally accomplished at approximately 30to 40 m.p.h. The gyroplane should then be allowed toaccelerate to VX for the initial climb, followed by VYfor the remainder of the climb. On any takeoff in agyroplane, engine torque causes the aircraft to rollopposite the direction of propeller rotation, and adequate compensation must be made.

CROSSWIND TAKEOFFA crosswind takeoff is much like a normal takeoff,except that you have to use the flight controls to compensate for the crosswind component. The termcrosswind component refers to that part of the windwhich acts at right angles to the takeoff path. Beforeattempting any crosswind takeoff, refer to the flightmanual, if available, or the manufacturer’s recommen-dations for any limitations.

Begin the maneuver by aligning the gyroplane into thewind as much as possible. At airports with wide runways, you might be able to angle your takeoff rolldown the runway to take advantage of as much head-wind as you can. As airspeed increases, gradually tiltthe rotor into the wind and use rudder pressure to maintain runway heading. In most cases, you shouldaccelerate to a speed slightly faster than normal liftoffspeed. As you reach takeoff speed, the downwind wheellifts off the ground first, followed by the upwind wheel.Once airborne, remove the cross-control inputs andestablish a crab, if runway heading is to be maintained.Due to the maneuverability of the gyroplane, an immedi-ate turn into the wind after lift off can be safely executed,if this does not cause a conflict with existing traffic.

COMMON ERRORS FOR NORMAL ANDCROSSWIND TAKEOFFS1. Failure to check rotor for proper operation, track,

and r.p.m. prior to takeoff.

2. Improper initial positioning of flight controls.

3. Improper application of power.

4. Poor directional control.

5. Failure to lift off at proper airspeed.

6. Failure to establish and maintain proper climbattitude and airspeed.

7. Drifting from the desired ground track during theclimb.

SHORT-FIELD TAKEOFFShort-field takeoff and climb procedures may berequired when the usable takeoff surface is short, orwhen it is restricted by obstructions, such as trees, powerlines, or buildings, at the departure end. Thetechnique is identical to the normal takeoff, with performance being optimized during each phase. Usingthe help from wind and propwash, the maximum rotorr.p.m. should be attained from the prerotator and full

Normally Aspirated—An engine that does not compensate for decreasesin atmospheric pressure through turbocharging or other means.

20-5

adjust the fuel/air mixture to achieve the best possiblepower output. This process is referred to as “leaningthe mixture.” If you are considering a high-altitudetakeoff, and it appears that the climb performance limitof the gyroplane is being approached, do not attempt atakeoff until more favorable conditions exist.

SOFT-FIELD TAKEOFFA soft field may be defined as any takeoff surface thatmeasurably retards acceleration during the takeoff roll.The objective of the soft-field takeoff is to transfer theweight of the aircraft from the landing gear to the rotoras quickly and smoothly as possible to eliminate thedrag caused by surfaces, such as tall grass, soft dirt, orsnow. This takeoff requires liftoff at a speed just abovethe minimum level flight speed for the aircraft. Due todesign, many of the smaller gyroplanes have a limitedpitch attitude available, as tail contact with the groundprevents high pitch attitudes until in flight. At mini-mum level flight speed, the pitch attitude is often suchthat the tail wheel is lower than the main wheels. Whenperforming a soft-field takeoff, these aircraft requireslightly higher liftoff airspeeds to allow for proper tailclearance.

COMMON ERRORS

1. Failure to check rotor for proper operation, track,and r.p.m. prior to takeoff.

2. Improper initial positioning of flight controls.

3. Improper application of power.

4. Allowing gyroplane to lose momentum by slowing or stopping on takeoff surface prior toinitiating takeoff.

5. Poor directional control.

6. Improper pitch attitude during lift-off.

7. Settling back to takeoff surface after becomingairborne.

8. Failure to establish and maintain proper climbattitude and airspeed.

9. Drifting from the desired ground track during theclimb.

JUMP TAKEOFFGyroplanes with collective pitch change, and the ability to prerotate the rotor system to speeds approxi-mately 50 percent higher than those required for normal flight, are capable of achieving extremely shorttakeoff rolls. Actual jump takeoffs can be performedunder the proper conditions. A jump takeoff requires noground roll, making it the most effective soft-field andcrosswind takeoff procedure. [Figure 20-5] A jumptakeoff is possible because the energy stored in theblades, as a result of the higher rotor r.p.m., is used tokeep the gyroplane airborne as it accelerates through

minimum level flight speed. Failure to have sufficientrotor r.p.m. for a jump takeoff results in the gyroplane settling back to the ground. Before attempting a jumptakeoff, it is essential that you first determine if it ispossible given the existing conditions by consulting therelevant performance chart. Should conditions ofweight, altitude, temperature, or wind leave the suc-cessful outcome of the maneuver in doubt, it should notbe attempted.

The prudent pilot may also use a “rule of thumb” forpredicting performance before attempting a jump take-off. As an example, suppose that a particular gyroplaneis known to be able to make a jump takeoff and remainairborne to accelerate to VX at a weight of 1,800 poundsand a density altitude of 2,000 feet. Since few takeoffsare made under these exact conditions, compensationmust be made for variations in weight, wind, and den-sity altitude. The “rule of thumb” being used for thisparticular aircraft stipulates that 1,000 feet of densityaltitude equates with 10 m.p.h. wind or 100 pounds ofgross weight. To use this equation, you must first deter-mine the density altitude. This is accomplished by setting your altimeter to the standard sea level pressuresetting of 29.92 inches of mercury and reading the pres-sure altitude. Next, you must correct for nonstandardtemperature. Standard temperature at sea level is 59°F(15°C) and decreases 3.5°F (2°C) for every additional

Figure 20-5. During a jump takeoff, excess rotor inertia isused to lift the gyroplane nearly vertical, where it is thenaccelerated through minimum level flight speed.

Density Altitude—Pressure altitude corrected for nonstandard temper-ature. This is a theoretical value that is used in determining aircraftperformance.

20-6

one thousand feet of pressure altitude. [Figure 20-6]Once you have determined the standard temperaturefor your pressure altitude, compare it with the actualexisting conditions. For every 10°F (5.5°C) the actualtemperature is above standard, add 750 feet to the pressure altitude to estimate the density altitude. If thedensity altitude is above 2,000 feet, a jump takeoff inthis aircraft should not be attempted unless wind and/ora weight reduction would compensate for the decreasein performance. Using the equation, if the density alti-tude is 3,000 feet (1,000 feet above a satisfactory jump density altitude), a reduction of 100 pounds in grossweight or a 10 m.p.h. of wind would still allow a satis-factory jump takeoff. Additionally, a reduction of 50pounds in weight combined with a 5 m.p.h. wind wouldalso allow a satisfactory jump. If it is determined that ajump takeoff should not be conducted because theweight cannot be reduced or an appropriate wind is notblowing, then consideration should be given to arolling takeoff. A takeoff roll of 10 m.p.h. is equivalentto a wind speed of 10 m.p.h. or a reduction of 100pounds in gross weight. It is important to note that ajump takeoff is predicated on having achieved a spe-cific rotor r.p.m. If this r.p.m. has not been attained,performance is unpredictable, and the maneuver shouldnot be attempted.

BASIC FLIGHT MANEUVERSConducting flight maneuvers in a gyroplane is differ-ent than in most other aircraft. Because of the wide

variety in designs, many gyroplanes have only basicinstruments available, and the pilot is often exposed tothe airflow. In addition, the visual clues found on otheraircraft, such as cowlings, wings, and windshieldsmight not be part of your gyroplane’s design.Therefore, much more reliance is placed on pilot interpretation of flight attitude and the “feel” of thegyroplane than in other types of aircraft. Acquiring theskills to precisely control a gyroplane can be a challenging and rewarding experience, but requiresdedication and the direction of a competent instructor.

STRAIGHT-AND-LEVEL FLIGHTStraight-and-level flight is conducted by maintaining aconstant altitude and a constant heading. In flight, agyroplane essentially acts as a plumb suspended fromthe rotor. As such, torque forces from the engine causethe airframe to be deflected a few degrees out of thevertical plane. This very slight “out of vertical” condition should be ignored and the aircraft flown tomaintain a constant heading.

The throttle is used to control airspeed. In level flight,when the airspeed of a gyroplane increases, the rotordisc angle of attack must be decreased. This causespitch control to become increasingly more sensitive.[Figure 20-7] As this disc angle becomes very small, itis possible to overcontrol a gyroplane when encounter-ing turbulence. For this reason, when extreme turbulence is encountered or expected, airspeed shouldbe decreased. Even in normal conditions, a gyroplanerequires constant attention to maintain straight-and-level flight. Although more stable than helicopters,gyroplanes are less stable than airplanes. When cyclictrim is available, it should be used to relieve any stickforces required during stabilized flight.

CLIMBS A climb is achieved by adding power in excess of whatis required for straight-and-level flight at a particularairspeed. The amount of excess power used is directlyproportional to the climb rate. For maneuvers when

Rotor Disk Angle

Low Speed

High Speed

F

Figure 20-7. The angle of the rotor disc decreases at highercruise speeds, which increases pitch control sensitivity.

20,00019,00018,00017,00016,00015,00014,00013,00012,00011,00010,0009,0008,0007,0006,0005,0004.0003,0002,0001,000

Sea Level

–25 –20 –15 –10 –5 0 5 10 15

–12 0 10 20 30 40 5950

°C

°F

Figure 20-6. Standard temperature chart.

20-7

maximum performance is desired, two important climbspeeds are best angle-of-climb speed and best rate-of-climb speed.

Because a gyroplane cannot be stalled, it may be tempt-ing to increase the climb rate by decreasing airspeed.This practice, however, is self-defeating. Operatingbelow the best angle-of-climb speed causes a diminish-ing rate of climb. In fact, if a gyroplane is slowed to theminimum level flight speed, it requires full power justto maintain altitude. Operating in this performancerealm, sometimes referred to as the “backside of thepower curve,” is desirable in some maneuvers, but canbe hazardous when maximum climb performance isrequired. For further explanation of a gyroplane powercurve, see Flight at Slow Airspeeds, which is discussedlater in this chapter.

DESCENTS A descent is the result of using less power than thatrequired for straight-and-level flight at a particular airspeed. Varying engine power during a descent allowsyou to choose a variety of descent profiles. In a power-offdescent, the minimum descent rate is achieved by usingthe airspeed that would normally be used for level flightat minimum power, which is also very close to the speedused for the best angle of climb. When distance is a factorduring a power-off descent, maximum gliding distancecan be achieved by maintaining a speed very close to thebest rate-of-climb airspeed. Because a gyroplane can besafely flown down to zero airspeed, a common error inthis type of descent is attempting to extend the glide byraising the pitch attitude. The result is a higher rate ofdescent and less distance being covered. For this reason,proper glide speed should be adhered to closely. Should astrong headwind exist, while attempting to achieve themaximum distance during a glide, a rule of thumb toachieve the greatest distance is to increase the glide speedby approximately 25 percent of the headwind. The atti-tude of the gyroplane for best glide performance islearned with experience, and slight pitch adjustments aremade for the proper airspeed. If a descent is needed tolose excess altitude, slowing the gyroplane to below thebest glide speed increases the rate of descent. Typically,slowing to zero airspeed results in a descent rate twicethat of maintaining the best glide speed.

TURNSTurns are made in a gyroplane by banking the rotor discwith cyclic control. Once the area, in the direction of theturn, has been cleared for traffic, apply sideward pres-sure on the cyclic until the desired bank angle isachieved. The speed at which the gyroplane enters thebank is dependent on how far the cyclic is displaced.When the desired bank angle is reached, return thecyclic to the neutral position. The rudder pedals are usedto keep the gyroplane in longitudinal trim throughoutthe turn, but not to assist in establishing the turn.

The bank angle used for a turn directly affects the rateof turn. As the bank is steepened, the turn rateincreases, but more power is required to maintain alti-tude. A bank angle can be reached where all availablepower is required, with any further increase in bankresulting in a loss of airspeed or altitude. Turns during aclimb should be made at the minimum angle of banknecessary, as higher bank angles would require morepower that would otherwise be available for the climb.Turns while gliding increase the rate of descent and maybe used as an effective way of losing excess altitude.

SLIPSA slip occurs when the gyroplane slides sidewaystoward the center of the turn. [Figure 20-8] It is causedby an insufficient amount of rudder pedal in the direc-tion of the turn, or too much in the direction oppositethe turn. In other words, holding improper rudder pedalpressure keeps the nose from following the turn, thegyroplane slips sideways toward the center of the turn.

SKIDSA skid occurs when the gyroplane slides sideways awayfrom the center of the turn. [Figure 20-9] It is caused bytoo much rudder pedal pressure in the direction of theturn, or by too little in the direction opposite the turn. Ifthe gyroplane is forced to turn faster with increasedpedal pressure instead of by increasing the degree of

Slip

InertiaHCL

Figure 20-8. During a slip, the rate of turn is too slow for theangle of bank used, and the horizontal component of lift(HCL) exceeds inertia. You can reestablish equilibrium bydecreasing the angle of bank, increasing the rate of turn byapplying rudder pedal, or a combination of the two.

Skid

HCL Inertia

Figure 20-9. During a skid, inertia exceeds the HCL. Toreestablish equilibrium, increase the bank angle or reducethe rate of turn by applying rudder pedal. You may also use acombination of these two corrections.

20-8

bank, it skids sideways away from the center of the turninstead of flying in its normal curved pattern.

COMMON ERRORS DURING BASIC FLIGHTMANEUVERS

1. Improper coordination of flight controls.

2. Failure to cross-check and correctly interpret outside and instrument references.

3. Using faulty trim technique.

STEEP TURNSA steep turn is a performance maneuver used in training that consists of a turn in either direction at abank angle of approximately 40°. The objective of performing steep turns is to develop smoothness, coor-dination, orientation, division of attention, and controltechniques.

Prior to initiating a steep turn, or any other flightmaneuver, first complete a clearing turn to check thearea for traffic. To accomplish this, you may executeeither one 180° turn or two 90° turns in opposite directions. Once the area has been cleared, roll thegyroplane into a 40° angle-of-bank turn whilesmoothly adding power and slowly moving the cyclicaft to maintain altitude. Maintain coordinated flightwith proper rudder pedal pressure. Throughout the turn,cross-reference visual cues outside the gyroplane withthe flight instruments, if available, to maintain a con-stant altitude and angle of bank. Anticipate the roll-outby leading the roll-out heading by approximately 20°.Using section lines or prominent landmarks to aid inorientation can be helpful in rolling out on the properheading. During roll-out, gradually return the cyclic tothe original position and reduce power to maintain altitude and airspeed.

COMMON ERRORS

1. Improper bank and power coordination duringentry and rollout.

2. Uncoordinated use of flight controls.

3. Exceeding manufacturer’s recommended maxi-mum bank angle.

4. Improper technique in correcting altitude deviations.

5. Loss of orientation.

6. Excessive deviation from desired heading duringrollout.

GROUND REFERENCE MANEUVERSGround reference maneuvers are training exercisesflown to help you develop a division of attentionbetween the flight path and ground references, whilecontrolling the gyroplane and watching for other

aircraft in the vicinity. Prior to each maneuver, a clear-ing turn should be accomplished to ensure the practicearea is free of conflicting traffic.

RECTANGULAR COURSEThe rectangular course is a training maneuver in whichthe ground track of the gyroplane is equidistant fromall sides of a selected rectangular area on the ground.[Figure 20-10] While performing the maneuver, thealtitude and airspeed should be held constant. The rec-tangular course helps you to develop a recognition of adrift toward or away from a line parallel to the intendedground track. This is helpful in recognizing drift towardor from an airport runway during the various legs of theairport traffic pattern.

For this maneuver, pick a square or rectangular field, oran area bounded on four sides by section lines or roads,where the sides are approximately a mile in length. Thearea selected should be well away from other air traf-fic. Fly the maneuver approximately 600 to 1,000 feetabove the ground, which is the altitude usually requiredfor an airport traffic pattern. You should fly the gyroplane parallel to and at a uniform distance, aboutone-fourth to one-half mile, from the field boundaries,not above the boundaries. For best results, positionyour flight path outside the field boundaries just farenough away that they may be easily observed. Youshould be able to see the edges of the selected fieldwhile seated in a normal position and looking out theside of the gyroplane during either a left-hand or right-hand course. The distance of the ground track from theedges of the field should be the same regardless ofwhether the course is flown to the left or right. All turnsshould be started when your gyroplane is abeam thecorners of the field boundaries. The bank normallyshould not exceed 30°.

Although the rectangular course may be entered fromany direction, this discussion assumes entry on a down-wind heading. As you approach the field boundary onthe downwind leg, you should begin planning for yourturn to the crosswind leg. Since you have a tailwind onthe downwind leg, the gyroplane’s groundspeed isincreased (position 1). During the turn onto the cross-wind leg, which is the equivalent of the base leg in atraffic pattern, the wind causes the gyroplane to driftaway from the field. To counteract this effect, the roll-in should be made at a fairly fast rate with a relativelysteep bank (position 2).

As the turn progresses, the tailwind componentdecreases, which decreases the groundspeed.Consequently, the bank angle and rate of turn must bereduced gradually to ensure that upon completion ofthe turn, the crosswind ground track continues to be thesame distance from the edge of the field. Upon comple-tion of the turn, the gyroplane should be level and

20-9

aligned with the downwind corner of the field.However, since the crosswind is now pushing youaway from the field, you must establish the proper driftcorrection by flying slightly into the wind. Therefore,the turn to crosswind should be greater than a 90°change in heading (position 3). If the turn has beenmade properly, the field boundary again appears to beone-fourth to one-half mile away. While on the cross-wind leg, the wind correction should be adjusted, asnecessary, to maintain a uniform distance from the fieldboundary (position 4).

As the next field boundary is being approached (posi-tion 5), plan the turn onto the upwind leg. Since a windcorrection angle is being held into the wind and towardthe field while on the crosswind leg, this next turnrequires a turn of less than 90°. Since the crosswindbecomes a headwind, causing the groundspeed todecrease during this turn, the bank initially must bemedium and progressively decreased as the turn pro-ceeds. To complete the turn, time the rollout so that thegyroplane becomes level at a point aligned with thecorner of the field just as the longitudinal axis of thegyroplane again becomes parallel to the field boundary(position 6). The distance from the field boundaryshould be the same as on the other sides of the field.

On the upwind leg, the wind is a headwind, whichresults in an decreased groundspeed (position 7).Consequently, enter the turn onto the next leg with afairly slow rate of roll-in, and a relatively shallow bank(position 8). As the turn progresses, gradually increasethe bank angle because the headwind component isdiminishing, resulting in an increasing groundspeed.During and after the turn onto this leg, the wind tendsto drift the gyroplane toward the field boundary. Tocompensate for the drift, the amount of turn must beless than 90° (position 9).

Again, the rollout from this turn must be such that asthe gyroplane becomes level, the nose of the gyroplaneis turned slightly away the field and into the wind tocorrect for drift. The gyroplane should again be thesame distance from the field boundary and at the samealtitude, as on other legs. Continue the crosswind leguntil the downwind leg boundary is approached (posi-tion 10). Once more you should anticipate drift andturning radius. Since drift correction was held on thecrosswind leg, it is necessary to turn greater than 90° toalign the gyroplane parallel to the downwind legboundary. Start this turn with a medium bank angle,gradually increasing it to a steeper bank as the turn pro-gresses. Time the rollout to assure paralleling the

WIND

No Crab

Start Turn At Boundary

Complete Turn At Boundary

Turn less Than 90°—Roll Out With Crab Established

Crab Into Wind

Start Turn At Boundary

Turn More Than 90°

Enter Pattern

Complete Turn At Boundary

No CrabStart Turn At Boundary

Turn More Than 90°—Roll Out With Crab Established

Complete Turn At Boundary

Crab Into Wind

Start Turn At Boundary

Turn Less Than 90°

Complete Turn At Boundary

Trac

kW

ithN

oW

ind

Cor

rect

ion

Figure 20-10. Rectangular course. The numbered positions in the text refer to the numbers in this illustration.

20-10

boundary of the field as the gyroplane becomes level(position 11).

If you have a direct headwind or tailwind on the upwindand downwind leg, drift should not be encountered.However, it may be difficult to find a situation wherethe wind is blowing exactly parallel to the field bound-aries. This makes it necessary to use a slight wind correction angle on all the legs. It is important to antici-pate the turns to compensate for groundspeed, drift, andturning radius. When the wind is behind the gyroplane,the turn must be faster and steeper; when it is ahead ofthe gyroplane, the turn must be slower and shallower.These same techniques apply while flying in an airporttraffic pattern.

S-TURNSAnother training maneuver you might use is the S-turn,which helps you correct for wind drift in turns. Thismaneuver requires turns to the left and right. The refer-ence line used, whether a road, railroad, or fence,should be straight for a considerable distance andshould extend as nearly perpendicular to the wind aspossible.

The object of S-turns is to fly a pattern of two half circles of equal size on opposite sides of the referenceline. [Figure 20-11] The maneuver should be performed at a constant altitude of 600 to 1,000 feetabove the terrain. S-turns may be started at any point;however, during early training it may be beneficial tostart on a downwind heading. Entering downwind permits the immediate selection of the steepest bank

that is desired throughout the maneuver. The discus-sion that follows is based on choosing a reference linethat is perpendicular to the wind and starting themaneuver on a downwind heading.

As the gyroplane crosses the reference line, immedi-ately establish a bank. This initial bank is the steepest

used throughout the maneuver since the gyroplane isheaded directly downwind and the groundspeed is at itshighest. Gradually reduce the bank, as necessary, todescribe a ground track of a half circle. Time the turnso that as the rollout is completed, the gyroplane iscrossing the reference line perpendicular to it and head-ing directly upwind. Immediately enter a bank in theopposite direction to begin the second half of the “S.”Since the gyroplane is now on an upwind heading, thisbank (and the one just completed before crossing thereference line) is the shallowest in the maneuver.Gradually increase the bank, as necessary, to describe aground track that is a half circle identical in size to theone previously completed on the other side of the refer-ence line. The steepest bank in this turn should beattained just prior to rollout when the gyroplane isapproaching the reference line nearest the downwindheading. Time the turn so that as the rollout is com-plete, the gyroplane is perpendicular to the referenceline and is again heading directly downwind.

In summary, the angle of bank required at any givenpoint in the maneuver is dependent on the ground-speed. The faster the groundspeed, the steeper thebank; the slower the groundspeed, the shallower the bank. To express it another way, the more nearlythe gyroplane is to a downwind heading, the steeper thebank; the more nearly it is to an upwind heading, theshallower the bank. In addition to varying the angle ofbank to correct for drift in order to maintain the properradius of turn, the gyroplane must also be flown with adrift correction angle (crab) in relation to its groundtrack; except of course, when it is on direct upwind ordownwind headings or there is no wind. One wouldnormally think of the fore and aft axis of the gyroplaneas being tangent to the ground track pattern at eachpoint. However, this is not the case. During the turn onthe upwind side of the reference line (side from whichthe wind is blowing), crab the nose of the gyroplanetoward the outside of the circle. During the turn on thedownwind side of the reference line (side of the refer-ence line opposite to the direction from which the windis blowing), crab the nose of the gyroplane toward theinside of the circle. In either case, it is obvious that thegyroplane is being crabbed into the wind just as it iswhen trying to maintain a straight ground track. Theamount of crab depends upon the wind velocity andhow nearly the gyroplane is to a crosswind position.The stronger the wind, the greater the crab angle at anygiven position for a turn of a given radius. The morenearly the gyroplane is to a crosswind position, thegreater the crab angle. The maximum crab angle shouldbe at the point of each half circle farthest from the reference line.

A standard radius for S-turns cannot be specified, sincethe radius depends on the airspeed of the gyroplane, the

Points of Shallowest Bank

Points of Steepest Bank

WIND

Figure 20-11. S-turns across a road.

20-11

velocity of the wind, and the initial bank chosen forentry.

TURNS AROUND A POINTThis training maneuver requires you to fly constantradius turns around a preselected point on the groundusing a maximum bank of approximately 40°, whilemaintaining a constant altitude. [Figure 20-12] Yourobjective, as in other ground reference maneuvers, is todevelop the ability to subconsciously control the gyro-plane while dividing attention between the flight pathand ground references, while still watching for otherair traffic in the vicinity.

The factors and principles of drift correction that areinvolved in S-turns are also applicable in this maneu-ver. As in other ground track maneuvers, a constantradius around a point will, if any wind exists, require aconstantly changing angle of bank and angles of windcorrection. The closer the gyroplane is to a directdownwind heading where the groundspeed is greatest,the steeper the bank, and the faster the rate of turnrequired to establish the proper wind correction angle.The more nearly it is to a direct upwind heading wherethe groundspeed is least, the shallower the bank, andthe slower the rate of turn required to establish the proper wind correction angle. It follows then, that throughout the maneuver, the bank and rate of turn must be gradually varied in proportion to the groundspeed.

The point selected for turns around a point should beprominent and easily distinguishable, yet small enoughto present a precise reference. Isolated trees,

crossroads, or other similar small landmarks are usu-ally suitable. The point should be in an area away fromcommunities, livestock, or groups of people on theground to prevent possible annoyance or hazard to others. Since the maneuver is performed between 600and 1,000 feet AGL, the area selected should alsoafford an opportunity for a safe emergency landing inthe event it becomes necessary.

To enter turns around a point, fly the gyroplane on adownwind heading to one side of the selected point at adistance equal to the desired radius of turn. When anysignificant wind exists, it is necessary to roll into theinitial bank at a rapid rate so that the steepest bank isattained abeam the point when the gyroplane is headeddirectly downwind. By entering the maneuver whileheading directly downwind, the steepest bank can beattained immediately. Thus, if a bank of 40° is desired,the initial bank is 40° if the gyroplane is at the correctdistance from the point. Thereafter, the bank is gradu-ally shallowed until the point is reached where thegyroplane is headed directly upwind. At this point, thebank is gradually steepened until the steepest bank isagain attained when heading downwind at the initialpoint of entry.

Just as S-turns require that the gyroplane be turned intothe wind, in addition to varying the bank, so do turnsaround a point. During the downwind half of the circle,the gyroplane’s nose must be progressively turnedtoward the inside of the circle; during the upwind half,the nose must be progressively turned toward the out-side. The downwind half of the turn around the pointmay be compared to the downwind side of the S-turn,while the upwind half of the turn around a point may becompared to the upwind side of the S-turn.

As you become experienced in performing turnsaround a point and have a good understanding of theeffects of wind drift and varying of the bank angle andwind correction angle, as required, entry into themaneuver may be from any point. When entering thismaneuver at any point, the radius of the turn must becarefully selected, taking into account the wind veloc-ity and groundspeed, so that an excessive bank is notrequired later on to maintain the proper ground track.

COMMON ERRORS DURING GROUNDREFERENCE MANEUVERS

1. Faulty entry technique.

2. Poor planning, orientation, or division of attention.

3. Uncoordinated flight control application.

4. Improper correction for wind drift.

UPP

ER HALF OF CIRCLE

DO

W

NWIND HALF OF CIRC

LE

Shallowest

Bank

Steeper Bank

Steepest

Bank

Shallower Bank

WIND

F

Figure 20-12. Turns around a point.

20-12

5. An unsymmetrical ground track during S-turnsacross a road.

6. Failure to maintain selected altitude or airspeed.

7. Selection of a ground reference where there is nosuitable emergency landing site.

FLIGHT AT SLOW AIRSPEEDSThe purpose of maneuvering during slow flight is tohelp you develop a feel for controlling the gyroplane atslow airspeeds, as well as gain an understanding of howload factor, pitch attitude, airspeed, and altitude controlrelate to each other.

Like airplanes, gyroplanes have a specific amount ofpower that is required for flight at various airspeeds, anda fixed amount of power available from the engine. Thisdata can be charted in a graph format. [Figure 20-13]The lowest point of the power required curve representsthe speed at which the gyroplane will fly in level flightwhile using the least amount of power. To fly faster thanthis speed, or slower, requires more power. While practicing slow flight in a gyroplane, you will likely beoperating in the performance realm on the chart that isleft of the minimum power required speed. This is oftenreferred to as the “backside of the power curve,” or flying “behind the power curve.” At these speeds, aspitch is increased to slow the gyroplane, more and morepower is required to maintain level flight. At the pointwhere maximum power available is being used, no further reduction in airspeed is possible without initiat-ing a descent. This speed is referred to as the minimumlevel flight speed. Because there is no excess poweravailable for acceleration, recovery from minimum levelflight speed requires lowering the nose of the gyroplaneand using altitude to regain airspeed. For this reason, it isessential to practice slow flight at altitudes that allowsufficient height for a safe recovery. Unintentionally flying a gyroplane on the backside of the power curveduring approach and landing can be extremely

hazardous. Should a go-around become necessary, sufficient altitude to regain airspeed and initiate a climbmay not be available, and ground contact may beunavoidable.

Flight at slow airspeeds is usually conducted at air-speeds 5 to 10 m.p.h. above the minimum level flightairspeed. When flying at slow airspeeds, it is importantthat your control inputs be smooth and slow to preventa rapid loss of airspeed due to the high drag increaseswith small changes in pitch attitude. In addition, turnsshould be limited to shallow bank angles. In order toprevent losing altitude during turns, power must beadded. Directional control remains very good whileflying at slow airspeeds, because of the high velocityslipstream produced by the increased engine power.

Recovery to cruise flight speed is made by loweringthe nose and increasing power. When the desired speedis reached, reduce power to the normal cruise powersetting.

COMMON ERRORS

1. Improper entry technique.

2. Failure to establish and maintain an appropriateairspeed.

3. Excessive variations of altitude and headingwhen a constant altitude and heading are specified.

4. Use of too steep a bank angle.

5. Rough or uncoordinated control technique.

HIGH RATE OF DESCENTA gyroplane will descend at a high rate when flown atvery low forward airspeeds. This maneuver may beentered intentionally when a steep descent is desired,and can be performed with or without power. An unin-tentional high rate of descent can also occur as a result

0 20 40 85 Airspeed, MPH

Power Available for Climb and Acceleration

Power Required

Engine Power Available at Full Throttle

Rat

eo

fC

limb

Des

cen

t 20 45 85

Power Required & Power Available vs. Airspeed Rates of Climb & Descent at Full Throttle

0 Airspeed, MPH

TYPICAL GYROPLANE

Hor

sepo

wer

Minimum Level Flight Speed

Figure 20-13. The low point on the power required curve is the speed that the gyroplane can fly while using the least amount ofpower, and is also the speed that will result in a minimum sink rate in a power-off glide.

20-13

of failing to monitor and maintain proper airspeed. Inpowered flight, if the gyroplane is flown below mini-mum level flight speed, a descent results even thoughfull engine power is applied. Further reducing the air-speed with aft cyclic increases the rate of descent. Forgyroplanes with a high thrust-to-weight ratio, thismaneuver creates a very high pitch attitude. To recover,the nose of the gyroplane must lowered slightly toexchange altitude for an increase in airspeed.

When operating a gyroplane in an unpowered glide,slowing to below the best glide speed can also result ina high rate of descent. As airspeed decreases, the rate ofdescent increases, reaching the highest rate as forwardspeed approaches zero. At slow airspeeds without theengine running, there is very little airflow over the tailsurfaces and rudder effectiveness is greatly reduced.Rudder pedal inputs must be exaggerated to maintaineffective yaw control. To recover, add power, if avail-able, or lower the nose and allow the gyroplane toaccelerate to the proper airspeed. This maneuverdemonstrates the importance of maintaining the properglide speed during an engine-out emergency landing.Attempting to stretch the glide by raising the noseresults in a higher rate of descent at a lower forwardspeed, leaving less distance available for the selectionof a landing site.

COMMON ERRORS

1. Improper entry technique.

2. Failure to recognize a high rate of descent.

3. Improper use of controls during recovery.

4. Initiation of recovery below minimum recoveryaltitude.

LANDINGSLandings may be classified according to the landingsurface, obstructions, and atmospheric conditions.Each type of landing assumes that certain conditionsexist. To meet the actual conditions, a combination oftechniques may be necessary.

NORMAL LANDINGThe procedure for a normal landing in a gyroplane ispredicated on having a prepared landing surface and nosignificant obstructions in the immediate area. Afterentering a traffic pattern that conforms to establishedstandards for the airport and avoids the flow of fixedwing traffic, a before landing checklist should bereviewed. The extent of the items on the checklist isdependent on the complexity of the gyroplane, and caninclude fuel, mixture, carburetor heat, propeller, engineinstruments, and a check for traffic.

Gyroplanes experience a slight lag between controlinput and aircraft response. This lag becomes more

apparent during the sensitive maneuvering requiredfor landing, and care must be taken to avoid overcor-recting for deviations from the desired approach path.After the turn to final, the approach airspeed appropri-ate for the gyroplane should be established. This speedis normally just below the minimum power requiredspeed for the gyroplane in level flight. During theapproach, maintain this airspeed by making adjust-ments to the gyroplane’s pitch attitude, as necessary.Power is used to control the descent rate.

Approximately 10 to 20 feet above the runway, beginthe flare by gradually increasing back pressure on thecyclic to reduce speed and decrease the rate of descent.The gyroplane should reach a near-zero rate of descentapproximately 1 foot above the runway with the powerat idle. Low airspeed combined with a minimum ofpropwash over the tail surfaces reduces rudder effectiveness during the flare. If a yaw moment isencountered, use whatever rudder control is requiredto maintain the desired heading. The gyroplane shouldbe kept laterally level and with the longitudinal axis inthe direction of ground track. Landing with sidewardmotion can damage the landing gear and must beavoided. In a full-flare landing, attempt to hold thegyroplane just off the runway by steadily increasingback pressure on the cyclic. This causes the gyroplaneto settle slowly to the runway in a slightly nose-highattitude as forward momentum dissipates.

Ground roll for a full-flare landing is typically under50 feet, and touchdown speed under 20 m.p.h. If a 20m.p.h. or greater headwind exists, it may be necessaryto decrease the length of the flare and allow the gyro-plane to touch down at a slightly higher airspeed toprevent it from rolling backward on landing. Aftertouchdown, rotor r.p.m. decays rather rapidly. Onlandings where brakes are required immediately aftertouchdown, apply them lightly, as the rotor is still car-rying much of the weight of the aircraft and too muchbraking causes the tires to skid.

SHORT-FIELD LANDING A short-field landing is necessary when you have a rel-atively short landing area or when an approach must bemade over obstacles that limit the available landingarea. When practicing short-field landings, assume youare making the approach and landing over a 50-footobstruction in the approach area.

To conduct a short-field approach and landing, fol-low normal procedures until you are established onthe final approach segment. At this point, use aftcyclic to reduce airspeed below the speed for mini-mum sink. By decreasing speed, sink rate increasesand a steeper approach path is achieved, minimizingthe distance between clearing the obstacle and

20-14

making contact with the surface. [Figure 20-14] Theapproach speed must remain fast enough, however,to allow the flare to arrest the forward and verticalspeed of the gyroplane. If the approach speed is toolow, the remaining vertical momentum will result ina hard landing. On a short-field landing with a slightheadwind, a touchdown with no ground roll is possi-ble. Without wind, the ground roll is normally lessthan 50 feet.

SOFT-FIELD LANDINGUse the soft-field landing technique when the landingsurface presents high wheel drag, such as mud, snow,sand, tall grass or standing water. The objective is totransfer the weight of the gyroplane from the rotor tothe landing gear as gently and slowly as possible. Witha headwind close to the touchdown speed of the gyroplane, a power approach can be made close to theminimum level flight speed. As you increase the nosepitch attitude just prior to touchdown, add additionalpower to cushion the landing. However, power shouldbe removed, just as the wheels are ready to touch. Thisresults is a very slow, gentle touchdown. In a strongheadwind, avoid allowing the gyroplane to roll rear-ward at touchdown. After touchdown, smoothly andgently lower the nosewheel to the ground. Minimizethe use of brakes, and remain aware that the nosewheelcould dig in the soft surface.

When no wind exists, use a steep approach similar to ashort-field landing so that the forward speed can be dis-sipated during the flare. Use the throttle to cushion thetouchdown.

CROSSWIND LANDING Crosswind landing technique is normally used in gyro-planes when a crosswind of approximately 15 m.p.h. orless exists. In conditions with higher crosswinds, itbecomes very difficult, if not impossible, to maintainadequate compensation for the crosswind. In these con-ditions, the slow touchdown speed of a gyroplaneallows a much safer option of turning directly into thewind and landing with little or no ground roll. Decidingwhen to use this technique, however, may be complicated by gusting winds or the characteristics ofthe particular landing area.

On final approach, establish a crab angle into the windto maintain a ground track that is aligned with theextended centerline of the runway. Just before touchdown, remove the crab angle and bank the gyroplane slightly into the wind to prevent drift.Maintain longitudinal alignment with the runway usingthe rudder. In higher crosswinds, if full rudder deflec-tion is not sufficient to maintain alignment with the run-way, applying a slight amount of power can increaserudder effectiveness. The length of the flare should bereduced to allow a slightly higher touchdown speed thanthat used in a no-wind landing. Touchdown is made onthe upwind main wheel first, with the other main wheelsettling to the runway as forward momentum is lost.After landing, continue to keep the rotor tilted into thewind to maintain positive control during the rollout.

HIGH-ALTITUDE LANDING A high-altitude landing assumes a density altitude nearthe limit of what is considered good climb performance

50'

Normal Approach

Short Field Approach

Figure 20-14. The airspeed used on a short-field approach is slower than that for a normal approach, allowing a steeperapproach path and requiring less runway.

20-15

for the gyroplane. When using the same indicated airspeed as that used for a normal approach at loweraltitude, a high density altitude results in higher rotorr.p.m. and a slightly higher rate of descent. The greatervertical velocity is a result of higher true airspeed ascompared with that at low altitudes. When practicinghigh-altitude landings, it is prudent to first learn normallandings with a flare and roll out. Full flare, no rolllandings should not be attempted until a good feel foraircraft response at higher altitudes has been acquired.As with high-altitude takeoffs, it is also important toconsider the effects of higher altitude on engine performance.

COMMON ERRORS DURING LANDING

1. Failure to establish and maintain a stabilizedapproach.

2. Improper technique in the use of power.

3. Improper technique during flare or touchdown.

4. Touchdown at too low an airspeed with strongheadwinds, causing a rearward roll.

5. Poor directional control after touchdown.

6. Improper use of brakes.

GO-AROUNDThe go-around is used to abort a landing approachwhen unsafe factors for landing are recognized. If thedecision is made early in the approach to go around,normal climb procedures utilizing VX and VY shouldbe used. A late decision to go around, such as after thefull flare has been initiated, may result in an airspeedwhere power required is greater than power available.When this occurs, a touchdown becomes unavoidableand it may be safer to proceed with the landing than tosustain an extended ground roll that would be required

to go around. Also, the pitch attitude of the gyroplanein the flare is high enough that the tail would be con-siderably lower than the main gear, and a touch downwith power on would result in a sudden pitch down andacceleration of the aircraft. Control of the gyroplaneunder these circumstances may be difficult.Consequently, the decision to go around should bemade as early as possible, before the speed is reducedbelow the point that power required exceeds poweravailable.

COMMON ERRORS

1. Failure to recognize a situation where a go-around is necessary.

2. Improper application of power.

3. Failure to control pitch attitude.

4. Failure to maintain recommended airspeeds.

5. Failure to maintain proper track during climb out.

AFTER LANDING AND SECURING The after-landing checklist should include such itemsas the transponder, cowl flaps, fuel pumps, lights, andmagneto checks, when so equipped. The rotor bladesdemand special consideration after landing, as turningrotor blades can be hazardous to others. Never enter anarea where people or obstructions are present with therotor turning. To assist the rotor in slowing, tilt thecyclic control into the prevailing wind or face the gyro-plane downwind. When slowed to under approximately75 r.p.m., the rotor brake may be applied, if available.Use caution as the rotor slows, as excess taxi speed orhigh winds could cause blade flap to occur. The bladesshould be depitched when taxiing if a collective controlis available. When leaving the gyroplane, alwayssecure the blades with a tiedown or rotor brake.

20-16

21-1

Gyroplanes are quite reliable, however emergencies dooccur, whether a result of mechanical failure or piloterror. By having a thorough knowledge of the gyroplane and its systems, you will be able to morereadily handle the situation. In addition, by knowingthe conditions which can lead to an emergency, manypotential accidents can be avoided.

ABORTED TAKEOFFPrior to every takeoff, consideration must be given to acourse of action should the takeoff become undesirableor unsafe. Mechanical failures, obstructions on thetakeoff surface, and changing weather conditions areall factors that could compromise the safety of a take-off and constitute a reason to abort. The decision toabort a takeoff should be definitive and made as soonas an unsafe condition is recognized. By initiating theabort procedures early, more time and distance will beavailable to bring the gyroplane to a stop. A late deci-sion to abort, or waiting to see if it will be necessary toabort, can result in a dangerous situation with little timeto respond and very few options available.

When initiating the abort sequence prior to thegyroplane leaving the surface, the procedure is quitesimple. Reduce the throttle to idle and allow the gyroplane to decelerate, while slowly applying aftcyclic for aerodynamic braking. This technique pro-vides the most effective braking and slows the aircraftvery quickly. If the gyroplane has left the surface whenthe decision to abort is made, reduce the throttle untilan appropriate descent rate is achieved. Once contactwith the surface is made, reduce the throttle to idle andapply aerodynamic braking as before. The wheelbrakes, if the gyroplane is so equipped, may be applied,as necessary, to assist in slowing the aircraft.

ACCELERATE/STOP DISTANCEAn accelerate/stop distance is the length of ground rollan aircraft would require to accelerate to takeoff speedand, assuming a decision to abort the takeoff is made,bring the aircraft safely to a stop. This value changesfor a given aircraft based on atmospheric conditions,the takeoff surface, aircraft weight, and other factorsaffecting performance. Knowing the accelerate/stopvalue for your gyroplane can be helpful in planning a

safe takeoff, but having this distance available does notnecessarily guarantee a safe aborted takeoff is possiblefor every situation. If the decision to abort is made afterliftoff, for example, the gyroplane will require consid-erably more distance to stop than the accelerate/stopfigure, which only considers the ground roll require-ment. Planning a course of action for an abort decisionat various stages of the takeoff is the best way to ensurethe gyroplane can be brought safely to a stop should theneed arise.

For a gyroplane without a flight manual or other pub-lished performance data, the accelerate/stop distancecan be reasonably estimated once you are familiar withthe performance and takeoff characteristics of the air-craft. For a more accurate figure, you can accelerate thegyroplane to takeoff speed, then slow to a stop, andnote the distance used. Doing this several times givesyou an average accelerate/stop distance. When per-formance charts for the aircraft are available, as in theflight manual of a certificated gyroplane, accurateaccelerate/stop distances under various conditions canbe determined by referring to the ground roll informa-tion contained in the charts.

LIFT-OFF AT LOW AIRSPEED ANDHIGH ANGLE OF ATTACKBecause of ground effect, your gyroplane might be ableto become airborne at an airspeed less than minimumlevel flight speed. In this situation, the gyroplane is fly-ing well behind the power curve and at such a highangle of attack that unless a correction is made, therewill be little or no acceleration toward best climbspeed. This condition is often encountered in gyroplanes capable of jump takeoffs. Jumping without sufficient rotor inertia to allow enough time to acceler-ate through minimum level flight speed, usually resultsin your gyroplane touching down after liftoff. If you dotouch down after performing a jump takeoff, youshould abort the takeoff.

During a rolling takeoff, if the gyroplane is forced intothe air too early, you could get into the same situation.It is important to recognize this situation and takeimmediate corrective action. You can either abort thetakeoff, if enough runway exists, or lower the nose and

21-2

accelerate to the best climb speed. If you choose to con-tinue the takeoff, verify that full power is applied, then,slowly lower the nose, making sure the gyroplane doesnot contact the surface. While in ground effect, acceler-ate to the best climb speed. Then, adjust the nose pitchattitude to maintain that airspeed.

COMMON ERRORSThe following errors might occur when practicing alift-off at a low airspeed.

1. Failure to check rotor for proper operation, track,and r.p.m. prior to initiating takeoff.

2. Use of a power setting that does not simulate a“behind the power curve” situation.

3. Poor directional control.

4. Rotation at a speed that is inappropriate for themaneuver.

5. Poor judgement in determining whether to abortor continue takeoff.

6. Failure to establish and maintain proper climbattitude and airspeed, if takeoff is continued.

7. Not maintaining the desired ground track duringthe climb.

PILOT-INDUCED OSCILLATION (PIO)Pilot-induced oscillation, sometimes referred to as por-poising, is an unintentional up-and-down oscillation ofthe gyroplane accompanied with alternating climbs anddescents of the aircraft. PIO is often the result of aninexperienced pilot overcontrolling the gyroplane, butthis condition can also be induced by gusty wind con-ditions. While this condition is usually thought of as alongitudinal problem, it can also happen laterally.

As with most other rotor-wing aircraft, gyroplanesexperience a slight delay between control input and thereaction of the aircraft. This delay may cause an inex-perienced pilot to apply more control input thanrequired, causing a greater aircraft response than wasdesired. Once the error has been recognized, oppositecontrol input is applied to correct the flight attitude.Because of the nature of the delay in aircraft response,it is possible for the corrections to be out of synchro-nization with the movements of the aircraft and aggra-vate the undesired changes in attitude. The result isPIO, or unintentional oscillations that can grow rapidlyin magnitude. [Figure 21-1]

In gyroplanes with an open cockpit and limited flightinstruments, it can be difficult for an inexperiencedpilot to recognize a level flight attitude due to the lackof visual references. As a result, PIO can develop as thepilot chases a level flight attitude and introduces climb-ing and descending oscillations. PIO can also developif a wind gust displaces the aircraft, and the controlinputs made to correct the attitude are out of phase withthe aircraft movements. Because the rotor disc angledecreases at higher speeds and cyclic control becomesmore sensitive, PIO is more likely to occur and can bemore pronounced at high airspeeds. To minimize thepossibility of PIO, avoid high-speed flight in gustyconditions, and make only small control inputs. Aftermaking a control input, wait briefly and observe thereaction of the aircraft before making another input. IfPIO is encountered, reduce power and place the cyclicin the position for a normal climb. Once the oscillationshave stopped, slowly return the throttle and cyclic totheir normal positions. The likelihood of encounteringPIO decreases greatly as experience is gained, and theability to subconsciously anticipate the reactions of thegyroplane to control inputs is developed.

Normal Flight

Variance from desired flight path recognized,

control input made to correct

Gyroplane reacts

Gyroplane reacts

Gyroplane reacts

Overcorrection recognized, larger control input made

to correct

Overcorrection recognized, larger input control made

to correct

Figure 21-1. Pilot-induced oscillation can result if the gyroplane’s reactions to control inputs are not anticipated and becomeout of phase.

21-3

BUNTOVER (POWER PUSHOVER)As you learned in Chapter 16—GyroplaneAerodynamics, the stability of a gyroplane is greatlyinfluenced by rotor force. If rotor force is rapidlyremoved, some gyroplanes have a tendency to pitchforward abruptly. This is often referred to as a forwardtumble, buntover, or power pushover. Removing therotor force is often referred to as unloading the rotor,and can occur if pilot-induced oscillations becomeexcessive, if extremely turbulent conditions areencountered, or the nose of the gyroplane is pushed for-ward rapidly after a steep climb.

A power pushover can occur on some gyroplanes thathave the propeller thrust line above the center of grav-ity and do not have an adequate horizontal stabilizer. Inthis case, when the rotor is unloaded, the propellerthrust magnifies the pitching moment around the centerof gravity. Unless a correction is made, this nose pitching action could become self-sustaining andirreversible. An adequate horizontal stabilizer slows thepitching rate and allows time for recovery.

Since there is some disagreement between manufactur-ers as to the proper recovery procedure for this situation, you must check with the manufacturer ofyour gyroplane. In most cases, you need to removepower and load the rotor blades. Some manufacturers,especially those with gyroplanes where the propellerthrust line is above the center of gravity, recommend thatyou need to immediately remove power in order to pre-vent a power pushover situation. Other manufacturersrecommend that you first try to load the rotor blades. Forthe proper positioning of the cyclic when loading up therotor blades, check with the manufacturer.

When compared to other aircraft, the gyroplane is justas safe and very reliable. The most important factor, asin all aircraft, is pilot proficiency. Proper training andflight experience helps prevent the risks associatedwith pilot-induced oscillation or buntover.

GROUND RESONANCEGround resonance is a potentially damaging aerody-namic phenomenon associated with articulated rotorsystems. It develops when the rotor blades move out ofphase with each other and cause the rotor disc tobecome unbalanced. If not corrected, ground resonancecan cause serious damage in a matter of seconds.

Ground resonance can only occur while the gyroplaneis on the ground. If a shock is transmitted to the rotorsystem, such as with a hard landing on one gear orwhen operating on rough terrain, one or more of theblades could lag or lead and allow the rotor system’scenter of gravity to be displaced from the center of rota-tion. Subsequent shocks to the other gear aggravate the

imbalance causing the rotor center of gravity to rotatearound the hub. This phenomenon is not unlike an out-of-balance washing machine. [Figure 21-2]

To reduce the chance of experiencing ground reso-nance, every preflight should include a check forproper strut inflation, tire pressure, and lag-leaddamper operation. Improper strut or tire inflation canchange the vibration frequency of the airframe, whileimproper damper settings change the vibration fre-quency of the rotor.

If you experience ground resonance, and the rotorr.p.m. is not yet sufficient for flight, apply the rotorbrake to maximum and stop the rotor as soon as possi-ble. If ground resonance occurs during takeoff, whenrotor r.p.m. is sufficient for flight, lift off immediately.Ground resonance cannot occur in flight, and the rotorblades will automatically realign themselves once thegyroplane is airborne. When prerotating the rotor sys-tem prior to takeoff, a slight vibration may be felt thatis a very mild form of ground resonance. Should thisoscillation amplify, discontinue the prerotation andapply maximum rotor brake.

EMERGENCY APPROACH ANDLANDINGThe modern engines used for powering gyroplanes aregenerally very reliable, and an actual mechanical mal-function forcing a landing is not a common occurrence.Failures are possible, which necessitates planning forand practicing emergency approaches and landings.The best way to ensure that important items are notoverlooked during an emergency procedure is to use achecklist, if one is available and time permits. Mostgyroplanes do not have complex electrical, hydraulic,or pneumatic systems that require lengthy checklists.In these aircraft, the checklist can be easily committedto memory so that immediate action can be taken if

Rotor Center of Gravity

122°

122° 116°

Figure 21-2. Taxiing on rough terrain can send a shock waveto the rotor system, resulting in the blades of a three-bladedrotor system moving from their normal 120° relationship toeach other.

21-4

needed. In addition, you should always maintain anawareness of your surroundings and be constantly onthe alert for suitable emergency landing sites.

When an engine failure occurs at altitude, the firstcourse of action is to adjust the gyroplane’s pitch atti-tude to achieve the best glide speed. This yields themost distance available for a given altitude, which inturn, allows for more possible landing sites. A commonmistake when learning emergency procedures isattempting to stretch the glide by raising the nose,which instead results in a steep approach path at a slowairspeed and a high rate of descent. [Figure 21-3] Onceyou have attained best glide speed, scan the area withingliding distance for a suitable landing site. Rememberto look behind the aircraft, as well as in front, makinggentle turns, if necessary, to see around the airframe.When selecting a landing site, you must consider thewind direction and speed, the size of the landing site,obstructions to the approach, and the condition of thesurface. A site that allows a landing into the wind andhas a firm, smooth surface with no obstructions is themost desirable. When considering landing on a road, bealert for powerlines, signs, and automobile traffic. Inmany cases, an ideal site will not be available, and itwill be necessary for you to evaluate your options andchoose the best alternative. For example, if a steadywind will allow a touchdown with no ground roll, itmay be acceptable to land in a softer field or in a

smaller area than would normally be considered. Onlanding, use short or soft field technique, as appropri-ate, for the site selected. A slightly higher-than-normalapproach airspeed may be required to maintain ade-quate airflow over the rudder for proper yaw control.

EMERGENCY EQUIPMENT ANDSURVIVAL GEAROn any flight not in the vicinity of an airport, it ishighly advisable to prepare a survival kit with itemsthat would be necessary in the event of an emergency.A properly equipped survival kit should be able to provide you with sustenance, shelter, medical care, anda means to summon help without a great deal of efforton your part. An efficient way to organize your survivalkit is to prepare a basic core of supplies that would benecessary for any emergency, and allow additionalspace for supplementary items appropriate for the terrain and weather you expect for a particular flight.The basic items to form the basis of your survival kitwould typically include: a first-aid kit and field medical guide, a flashlight, water, a knife, matches,some type of shelter, and a signaling device. Additionalitems that may be added to meet the conditions, forexample, would be a lifevest for a flight over water, orheavy clothing for a flight into cold weather. Anotherconsideration is carrying a cellular phone. Severalpilots have been rescued after calling someone to indicate there had been an accident.

Best Glide Speed

Too Fast

Too

Slow

Figure 21-3. Any deviation from best glide speed will reduce the distance you can glide and may cause you to land short of asafe touchdown point.

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As with any aircraft, the ability to pilot a gyroplanesafely is largely dependent on the capacity of the pilotto make sound and informed decisions. To this end,techniques have been developed to ensure that a pilotuses a systematic approach to making decisions, andthat the course of action selected is the most appropri-ate for the situation. In addition, it is essential that youlearn to evaluate your own fitness, just as you evaluatethe airworthiness of your aircraft, to ensure that yourphysical and mental condition is compatible with a safeflight. The techniques for acquiring these essentialskills are explained in depth in Chapter 14—Aeronautical Decision Making (Helicopter).

As explained in Chapter 14, one of the best methods todevelop your aeronautical decision making is learningto recognize the five hazardous attitudes, and how tocounteract these attitudes. [Figure 22-1] This chapterfocuses on some examples of how these hazardous atti-tudes can apply to gyroplane operations.

IMPULSIVITYGyroplanes are a class of aircraft which can be acquired,constructed, and operated in ways unlike most other air-craft. This inspires some of the most exciting andrewarding aspects of flying, but it also creates a uniqueset of dangers to which a gyroplane pilot must be alert.For example, a wide variety of amateur-built gyroplanesare available, which can be purchased in kit form and

assembled at home. This makes the airworthiness ofthese gyroplanes ultimately dependent on the vigilanceof the one assembling and maintaining the aircraft.Consider the following scenario.

Jerry recently attended an airshow that had a gyro-plane flight demonstration and a number of gyroplaneson display. Being somewhat mechanically inclined andretired with available spare time, Jerry decided thatbuilding a gyroplane would be an excellent project forhim and ordered a kit that day. When the kit arrived,Jerry unpacked it in his garage and immediately beganthe assembly. As the gyroplane neared completion,Jerry grew more excited at the prospect of flying an air-craft that he had built with his own hands. When thegyroplane was nearly complete, Jerry noticed that arudder cable was missing from the kit, or perhaps lostduring the assembly. Rather than contacting the manu-facturer and ordering a replacement, which Jerrythought would be a hassle and too time consuming, hewent to his local hardware store and purchased somecable he thought would work. Upon returning home, hewas able to fashion a rudder cable that seemed func-tional and continued with the assembly.

Jerry is exhibiting “impulsivity.” Rather than taking thetime to properly build his gyroplane to the specifica-tions set forth by the manufacturer, Jerry let his excitement allow him to cut corners by acting onimpulse, rather than taking the time to think the matterthrough. Although some enthusiasm is normal duringassembly, it should not be permitted to compromise theairworthiness of the aircraft. Manufacturers often usehigh quality components, which are constructed andtested to standards much higher than those found inhardware stores. This is particularly true in the area ofcables, bolts, nuts, and other types of fasteners wherestrength is essential. The proper course of action Jerryshould have taken would be to stop, think, and considerthe possible consequences of making an impulsivedecision. Had he realized that a broken rudder cable in flight could cause a loss of control ofthe gyroplane, he likely would have taken the time tocontact the manufacturer and order a cable that met thedesign specifications.

INVULNERABILITYAnother area that can often lead to trouble for a gyro-plane pilots is the failure to obtain adequate flight

HAZARDOUS ATTITUDE ANTIDOTE

Anti-authority: "Don't tell me!"

"Follow the rules. They are usually right."

Impulsivity: "Do something—quickly!" "Not so fast. Think first."

Invulnerability: "It won't happen to me!" "It could happen to me."

Macho: "I can do it." "Taking chances is foolish."

Resignation: "What's the use?"

"I'm not helpless. I can make the difference."

Figure 22-1. To overcome hazardous attitudes, you mustmemorize the antidotes for each of them. You should knowthem so well that they will automatically come to mind whenyou need them.

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instruction to operate their gyroplane safely. This canbe the result of people thinking that because they canbuild the machine themselves, it must be simpleenough to learn how to fly by themselves. Other reasons that can lead to this problem can be simplymonetary, in not wanting to pay the money for adequateinstruction, or feeling that because they are qualified inanother type of aircraft, flight instruction is not neces-sary. In reality, gyroplane operations are quite unique,and there is no substitute for adequate training by acompetent and authorized instructor. Consider the following scenario.

Jim recently met a coworker who is a certified pilot andowner of a two-seat gyroplane. In discussing the gyro-plane with his coworker, Jim was fascinated andreminded of his days in the military as a helicopterpilot many years earlier. When offered a ride, Jim read-ily accepted. He met his coworker at the airport the following weekend for a short flight and was immedi-ately hooked. After spending several weeks researchingavailable designs, Jim decided on a particular gyroplane and purchased a kit. He had it assembled ina few months, with the help and advice of his new friendand fellow gyroplane enthusiast. When the gyroplanewas finally finished, Jim asked his friend to take himfor a ride in his two-seater to teach him the basics offlying. The rest, he said, he would figure out while flying his own machine from a landing strip that he hadfashioned in a field behind his house.

Jim is unknowingly inviting disaster by allowing him-self to be influenced by the hazardous attitude of“invulnerability.” Jim does not feel that it is possible tohave an accident, probably because of his past experi-ence in helicopters and from witnessing the ease withwhich his coworker controlled the gyroplane on theirflight together. What Jim is failing to consider, how-ever, is the amount of time that has passed since he wasproficient in helicopters, and the significant differencesbetween helicopter and gyroplane operations. He isalso overlooking the fact that his friend is a certificatedpilot, who has taken a considerable amount of instruc-tion to reach his level of competence. Without adequateinstruction and experience, Jim could, for example,find himself in a pilot-induced oscillation withoutknowing the proper technique for recovery, whichcould ultimately be disastrous. The antidote for an attitude of invulnerability is to realize that accidentscan happen to anyone.

MACHODue to their unique design, gyroplanes are quiteresponsive and have distinct capabilities. Althoughgyroplanes are capable of incredible maneuvers, theydo have limitations. As gyroplane pilots grow morecomfortable with their machines, they might be

tempted to operate progressively closer to the edge ofthe safe operating envelope. Consider the followingscenario.

Pat has been flying gyroplanes for years and has anexcellent reputation as a skilled pilot. He has recentlybuilt a high performance gyroplane with an advancedrotor system. Pat was excited to move into a moreadvanced aircraft because he had seen the same designperforming aerobatics in an airshow earlier that year.He was amazed by the capability of the machine. Hehad always felt that his ability surpassed the capabilityof the aircraft he was flying. He had invested a largeamount of time and resources into the construction ofthe aircraft, and, as he neared completion of the assem-bly, he was excited about the opportunity of showinghis friends and family his capabilities.

During the first few flights, Pat was not completelycomfortable in the new aircraft, but he felt that he wasprogressing through the transition at a much fasterpace than the average pilot. One morning, when he waswith some of his fellow gyroplane enthusiasts, Patbegan to brag about the superior handling qualities ofthe machine he had built. His friends were very excited,and Pat realized that they would be expecting quite ashow on his next flight. Not wanting to disappoint them,he decided that although it might be early, he wouldgive the spectators on the ground a real show. On hisfirst pass he came down fairly steep and fast and recov-ered from the dive with ease. Pat then decided to makeanother pass only this time he would come in muchsteeper. As he began to recover, the aircraft did notclimb as he expected and almost settled to the ground.Pat narrowly escaped hitting the spectators as he was trying to recover from the dive.

Pat had let the “macho” hazardous attitude influencehis decision making. He could have avoided the conse-quences of this attitude if he had stopped to think thattaking chances is foolish.

RESIGNATIONSome of the elements pilots face cannot be controlled.Although we cannot control the weather, we do havesome very good tools to help predict what it will do,and how it can affect our ability to fly safely. Goodpilots always make decisions that will keep theiroptions open if an unexpected event occurs while flying. One of the greatest resources we have in thecockpit is the ability to improvise and improve theoverall situation even when a risk element jeopardizesthe probability of a successful flight. Consider the fol-lowing scenario.

Judi flies her gyroplane out of a small grass strip onher family’s ranch. Although the rugged landscape ofthe ranch lends itself to the remarkable scenery, it

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leaves few places to safely land in the event of an emer-gency. The only suitable place to land other than thegrass strip is to the west on a smooth section of the roadleading to the house. During Judi’s training, her trafficpatterns were always made with left turns. Figuringthis was how she was to make all traffic patterns, sheapplied this to the grass strip at the ranch. In addition,she was uncomfortable with making turns to the right.Since, the wind at the ranch was predominately fromthe south, this meant that the traffic pattern was to theeast of the strip.

Judi’s hazardous attitude is “resignation.” She hasaccepted the fact that her only course of action is to flyeast of the strip, and if an emergency happens, there isnot much she can do about it. The antidote to this hazardous attitude is “I’m not helpless, I can make a dif-ference.” Judi could easily modify her traffic pattern sothat she is always within gliding distance of a suitable landing area. In addition, if she was uncomfort-able with a maneuver, she could get additional training.

ANTI-AUTHORITYRegulations are implemented to protect aviation personnel as well as the people who are not involved inaviation. Pilots who choose to operate outside of the

regulations, or on the ragged edge, eventually getcaught, or even worse, they end up having an accident.Consider the following scenario.

Dick is planning to fly the following morning and real-izes that his medical certificate has expired. He knowsthat he will not have time to take a flight physicalbefore his morning flight. Dick thinks to himself “Therules are too restrictive. Why should I spend the timeand money on a physical when I will be the only one atrisk if I fly tomorrow?”

Dick decides to fly the next morning thinking that noharm will come as long as no one finds out that he isflying illegally. He pulls his gyroplane out from thehangar, does the preflight inspection, and is gettingready to start the engine when an FAA inspector walksup and greets him. The FAA inspector is conducting arandom inspection and asks to see Dick’s pilot andmedical certificates.

Dick subjected himself to the hazardous attitude of “anti-authority.” Now, he will be unable to fly, and has invitedan exhaustive review of his operation by the FAA. Dickcould have prevented this event if had taken the time tothink, “Follow the rules. They are usually right.”

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ABSOLUTE ALTITUDE—The act-ual distance an object is above theground.

ADVANCING BLADE—The blademoving in the same direction as thehelicopter or gyroplane. In rotorcraftthat have counterclockwise main rotorblade rotation as viewed from above,the advancing blade is in the right halfof the rotor disc area during forwardmovement.

AIRFOIL—Any surface designed toobtain a useful reaction of lift, or neg-ative lift, as it moves through the air.

AGONIC LINE—A line along whichthere is no magnetic variation.

AIR DENSITY—The density of theair in terms of mass per unit volume.Dense air has more molecules per unitvolume than less dense air. The densi-ty of air decreases with altitude abovethe surface of the earth and withincreasing temperature.

AIRCRAFT PITCH—When refer-enced to an aircraft, it is the move-ment about its lateral, or pitch axis.Movement of the cyclic forward or aftcauses the nose of the helicopter orgyroplane to pitch up or down.

AIRCRAFT ROLL—Is the move-ment of the aircraft about its longitudinal axis. Movement of thecyclic right or left causes the helicop-ter or gyroplane to tilt in that direction.

AIRWORTHINESS DIRECTIVE—When an unsafe condition existswith an aircraft, the FAA issues an air-worthiness directive to notify con-cerned parties of the condition and todescribe the appropriate correctiveaction.

ALTIMETER—An instrument thatindicates flight altitude by sensingpressure changes and displaying alti-tude in feet or meters.

ANGLE OF ATTACK—The anglebetween the airfoil’s chord line andthe relative wind.

ANTITORQUE PEDAL—The pedalused to control the pitch of the tailrotor or air diffuser in a NOTAR®system.

ANTITORQUE ROTOR—See tailrotor.

ARTICULATED ROTOR—A rotorsystem in which each of the blades isconnected to the rotor hub in such away that it is free to change its pitchangle, and move up and down andfore and aft in its plane of rotation.

AUTOPILOT—Those units andcomponents that furnish a means ofautomatically controlling the aircraft.

AUTOROTATION—The conditionof flight during which the main rotoris driven only by aerodynamic forceswith no power from the engine.

AXIS-OF-ROTATION—The imagi-nary line about which the rotorrotates. It is represented by a linedrawn through the center of, and per-pendicular to, the tip-path plane.

BASIC EMPTY WEIGHT—Theweight of the standard rotorcraft,operational equipment, unusable fuel,and full operating fluids, includingfull engine oil.

BLADE CONING—An upwardsweep of rotor blades as a result of liftand centrifugal force.

BLADE DAMPER—A deviceattached to the drag hinge to restrainthe fore and aft movement of the rotorblade.

BLADE FEATHER OR FEATH-ERING—The rotation of the bladearound the spanwise (pitch change)axis.

BLADE FLAP—The ability of therotor blade to move in a vertical direc-tion. Blades may flap independentlyor in unison.

BLADE GRIP—The part of the hubassembly to which the rotor blades areattached, sometimes referred to asblade forks.

BLADE LEAD OR LAG—The foreand aft movement of the blade in theplane of rotation. It is sometimescalled hunting or dragging.

BLADE LOADING—The loadimposed on rotor blades, determinedby dividing the total weight of the hel-icopter by the combined area of all therotor blades.

BLADE ROOT—The part of theblade that attaches to the blade grip.

BLADE SPAN—The length of ablade from its tip to its root.

BLADE STALL—The condition ofthe rotor blade when it is operating atan angle of attack greater than themaximum angle of lift.

BLADE TIP—The further most partof the blade from the hub of the rotor.

BLADE TRACK—The relationshipof the blade tips in the plane of rota-tion. Blades that are in track will movethrough the same plane of rotation.

BLADE TRACKING—The mechan-ical procedure used to bring the bladesof the rotor into a satisfactory relation-ship with each other under dynamicconditions so that all blades rotate on acommon plane.

BLADE TWIST—The variation inthe angle of incidence of a bladebetween the root and the tip.

BLOWBACK—The tendency of therotor disc to tilt aft in forward flight asa result of flapping.

GLOSSARY

G-2

BUNTOVER—The tendency of agyroplane to pitch forward when rotorforce is removed.

CALIBRATED AIRSPEED (CAS)—Indicated airspeed of an aircraft,corrected for installation and instru-mentation errors.

CENTER OF GRAVITY—The the-oretical point where the entire weightof the helicopter is considered to beconcentrated.

CENTER OF PRESSURE—Thepoint where the resultant of all theaerodynamic forces acting on an air-foil intersects the chord.

CENTRIFUGAL FORCE—Theapparent force that an object movingalong a circular path exerts on thebody constraining the object and thatacts outwardly away from the centerof rotation.

CENTRIPETAL FORCE—Theforce that attracts a body toward itsaxis of rotation. It is opposite centrifu-gal force.

CHIP DETECTOR—A warningdevice that alerts you to any abnormalwear in a transmission or engine. Itconsists of a magnetic plug locatedwithin the transmission. The magnetattracts any metal particles that havecome loose from the bearings or othertransmission parts. Most chip detec-tors have warning lights located on theinstrument panel that illuminate whenmetal particles are picked up.

CHORD—An imaginary straight linebetween the leading and trailing edgesof an airfoil section.

CHORDWISE AXIS—A term usedin reference to semirigid rotorsdescribing the flapping or teeteringaxis of the rotor.

COAXIL ROTOR—A rotor systemutilizing two rotors turning in oppositedirections on the same centerline. Thissystem is used to eliminated the needfor a tail rotor.

COLLECTIVE PITCH CON-TROL—The control for changing thepitch of all the rotor blades in the mainrotor system equally and simultane-ously and, consequently, the amountof lift or thrust being generated.

CONING—See blade coning.

CORIOLIS EFFECT—The tenden-cy of a rotor blade to increase ordecrease its velocity in its plane ofrotation when the center of massmoves closer or further from the axisof rotation.

CYCLIC FEATHERING—Themechanical change of the angle ofincidence, or pitch, of individual rotorblades independently of other bladesin the system.

CYCLIC PITCH CONTROL—Thecontrol for changing the pitch of eachrotor blade individually as it rotatesthrough one cycle to govern the tilt ofthe rotor disc and, consequently, thedirection and velocity of horizontalmovement.

DELTA HINGE—A flapping hingewith a skewed axis so that the flappingmotion introduces a component offeathering that would result in a restor-ing force in the flap-wise direction.

DENSITY ALTITUDE—Pressurealtitude corrected for nonstandardtemperature variations.

DEVIATION—A compass errorcaused by magnetic disturbances fromthe electrical and metal components inthe aircraft. The correction for thiserror is displayed on a compass cor-rection card place near the magneticcompass of the aircraft.

DIRECT CONTROL—The abilityto maneuver a rotorcraft by tilting therotor disc and changing the pitch ofthe rotor blades.

DIRECT SHAFT TURBINE—Ashaft turbine engine in which the com-pressor and power section are mount-ed on a common driveshaft.

DISC AREA—The area swept by theblades of the rotor. It is a circle withits center at the hub and has a radius ofone blade length.

DISC LOADING—The total heli-copter weight divided by the rotor discarea.

DISSYMMETRY OF LIFT—Theunequal lift across the rotor discresulting from the difference in thevelocity of air over the advancingblade half and retreating blade half ofthe rotor disc area.

DRAG—An aerodynamic force on abody acting parallel and opposite torelative wind.

DUAL ROTOR—A rotor system uti-lizing two main rotors.

DYNAMIC ROLLOVER—The ten-dency of a helicopter to continuerolling when the critical angle isexceeded, if one gear is on the ground,and the helicopter is pivoting aroundthat point.

FEATHERING—The action thatchanges the pitch angle of the rotorblades by rotating them around theirfeathering (spanwise) axis.

FEATHERING AXIS—The axisabout which the pitch angle of a rotorblade is varied. Sometimes referred toas the spanwise axis.

FEEDBACK—The transmittal offorces, which are initiated by aerody-namic action on rotor blades, to thecockpit controls.

FLAPPING HINGE—The hingethat permits the rotor blade to flap andthus balance the lift generated by theadvancing and retreating blades.

FLAPPING—The vertical move-ment of a blade about a flappinghinge.

FLARE—A maneuver accomplishedprior to landing to slow down a rotor-craft.

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FREE TURBINE—A turboshaftengine with no physical connectionbetween the compressor and poweroutput shaft.

FREEWHEELING UNIT—A com-ponent of the transmission or powertrain that automatically disconnectsthe main rotor from the engine whenthe engine stops or slows below theequivalent rotor r.p.m.

FULLY ARTICULATED ROTORSYSTEM—See articulated rotor sys-tem.

GRAVITY—See weight.

GROSS WEIGHT—The sum of thebasic empty weight and useful load.

GROUND EFFECT—A usuallybeneficial influence on rotorcraft per-formance that occurs while flyingclose to the ground. It results from areduction in upwash, downwash, andbladetip vortices, which provide a cor-responding decrease in induced drag.

GROUND RESONANCE—Self-excited vibration occurring wheneverthe frequency of oscillation of theblades about the lead-lag axis of anarticulated rotor becomes the same asthe natural frequency of the fuselage.

G Y R O C O P T E R — Tr a d e m a r kapplied to gyroplanes designed andproduced by the Bensen AircraftCompany.

GYROSCOPIC PRECESSION—An inherent quality of rotating bodies,which causes an applied force to bemanifested 90° in the direction ofrotation from the point where theforce is applied.

HUMAN FACTORS—The study ofhow people interact with their environment. In the case of generalaviation, it is the study of how pilotperformance is influenced by suchissues as the design of cockpits, thefunction of the organs of the body, theeffects of emotions, and the interac-

tion and communication with otherparticipants in the aviation communi-ty, such as other crew members and airtraffic control personnel.

HUNTING—Movement of a bladewith respect to the other blades in theplane of rotation, sometimes calledleading or lagging.

INERTIA—The property of matterby which it will remain at rest or in astate of uniform motion in the samedirection unless acted upon by someexternal force.

IN GROUND EFFECT (IGE)HOVER—Hovering close to the sur-face (usually less than one rotor diam-eter distance above the surface) underthe influence of ground effect.

INDUCED DRAG—That part of thetotal drag that is created by the pro-duction of lift.

INDUCED FLOW—The componentof air flowing vertically through therotor system resulting from the pro-duction of lift.

ISOGONIC LINES—Lines oncharts that connect points of equalmagnetic variation.

KNOT—A unit of speed equal to onenautical mile per hour.

L/DMAX—The maximum ratio

between total lift (L) and total drag(D). This point provides the best glidespeed. Any deviation from the bestglide speed increases drag and reducesthe distance you can glide.

LATERIAL VIBRATION—A vibra-tion in which the movement is in a lat-eral direction, such as imbalance of themain rotor.

LEAD AND LAG—The fore (lead)and aft (lag) movement of the rotorblade in the plane of rotation.

LICENSED EMPTY WEIGHT—Basic empty weight not including fullengine oil, just undrainable oil.

LIFT—One of the four main forcesacting on a rotorcraft. It acts perpendi-cular to the relative wind.

LOAD FACTOR—The ratio of aspecified load to the total weight ofthe aircraft.

MARRIED NEEDLES—A termused when two hands of an instrumentare superimposed over each other, ason the engine/rotor tachometer.

MAST—The component that sup-ports the main rotor.

MAST BUMPING—Action of therotor head striking the mast, occurringon underslung rotors only.

MINIMUM LEVEL FLIGHTSPEED—The speed below which agyroplane, the propeller of which isproducing maximum thrust, loses alti-tude.

NAVIGATIONAL AID (NAVAID)—Any visual or electronic device, air-borne or on the surface, that providespoint-to-point guidance information,or position data, to aircraft in flight.

NIGHT—The time between the endof evening civil twilight and thebeginning of morning civil twilight, aspublished in the American AirAlmanac.

NORMALLY ASPIRATED ENGINE—An engine that does not compen-sate for decreases in atmospheric pres-sure through turbocharging or othermeans.

ONE-TO-ONE VIBRATION—Alow frequency vibration having onebeat per revolution of the rotor. Thisvibration can be either lateral, vertical,or horizontal.

OUT OF GROUND EFFECT(OGE) HOVER—Hovering greaterthan one diameter distance above thesurface. Because induced drag isgreater while hovering out of groundeffect, it takes more power to achievea hover out of ground effect.

G-4

PARASITE DRAG—The part oftotal drag created by the form or shapeof helicopter parts.

PAYLOAD—The term used for pas-sengers, baggage, and cargo.

PENDULAR ACTION—The lateralor longitudinal oscillation of the fuse-lage due to it being suspended fromthe rotor system.

PITCH ANGLE—The angle betweenthe chord line of the rotor blade andthe reference plane of the main rotorhub or the rotor plane of rotation.

PREROTATION—In a gyroplane, itis the spinning of the rotor to a suffi-cient r.p.m. prior to flight.

PRESSURE ALTITUDE—The heightabove the standard pressure level of29.92 in. Hg. It is obtained by setting29.92 in the barometric pressure win-dow and reading the altimeter.

PROFILE DRAG—Drag incurredfrom frictional or parasitic resistanceof the blades passing through the air. Itdoes not change significantly with theangle of attack of the airfoil section,but it increases moderately as airspeedincreases.

RESULTANT RELATIVE WIND—Airflow from rotation that is modifiedby induced flow.

RETREATING BLADE—Any blade,located in a semicircular part of the rotordisc, where the blade direction is oppo-site to the direction of flight.

RETREATING BLADE STALL—A stall that begins at or near the tip ofa blade in a helicopter because of thehigh angles of attack required to com-pensate for dissymmetry of lift. In agyroplane the stall occurs at 20 to 40percent outboard from the hub.

RIGID ROTOR—A rotor systempermitting blades to feather but notflap or hunt.

ROTATIONAL VELOCITY—Thecomponent of relative wind producedby the rotation of the rotor blades.

ROTOR—A complete system ofrotating airfoils creating lift for a heli-copter or gyroplane.

ROTOR DISC AREA—See diskarea.

ROTOR BRAKE—A device used tostop the rotor blades during shutdown.

ROTOR FORCE—The force pro-duced by the rotor in a gyroplane. It iscomprised of rotor lift and rotor drag.

SEMIRIGID ROTOR—A rotor sys-tem in which the blades are fixed to thehub but are free to flap and feather.

SETTLING WITH POWER—Seevortex ring state.

SHAFT TURBINE—A turbineengine used to drive an output shaftcommonly used in helicopters.

SKID—A flight condition in whichthe rate of turn is too great for theangle of bank.

SKID SHOES—Plates attached tothe bottom of skid landing gear pro-tecting the skid.

SLIP—A flight condition in whichthe rate of turn is too slow for theangle of bank.

SOLIDITY RATIO—The ratio ofthe total rotor blade area to total rotordisc area.

SPAN—The dimension of a rotorblade or airfoil from root to tip.

SPLIT NEEDLES—A term used todescribe the position of the two nee-dles on the engine/rotor tachometerwhen the two needles are not superim-posed.

STANDARD ATMOSPHERE—Ahypothetical atmosphere based onaverages in which the surface temper-ature is 59°F (15°C), the surface pres-sure is 29.92 in. Hg (1013.2 Mb) atsea level, and the temperature lapserate is approximately 3.5°F (2°C) per1,000 feet.

STATIC STOP—A device used tolimit the blade flap, or rotor flap, atlow r.p.m. or when the rotor isstopped.

STEADY-STATE FLIGHT—A con-dition when a rotorcraft is in straight-and-level, unaccelerated flight, and allforces are in balance.

SYMMETRICAL AIRFOIL—Anairfoil having the same shape on thetop and bottom.

TAIL ROTOR—A rotor turning in aplane perpendicular to that of the mainrotor and parallel to the longitudinalaxis of the fuselage. It is used to con-trol the torque of the main rotor and toprovide movement about the yaw axisof the helicopter.

TEETERING HINGE—A hingethat permits the rotor blades of a semi-rigid rotor system to flap as a unit.

THRUST—The force developed bythe rotor blades acting parallel to therelative wind and opposing the forcesof drag and weight.

TIP-PATH PLANE—The imaginarycircular plane outlined by the rotorblade tips as they make a cycle ofrotation.

TORQUE—In helicopters with a sin-gle, main rotor system, the tendency ofthe helicopter to turn in the oppositedirection of the main rotor rotation.

TRAILING EDGE—The rearmostedge of an airfoil.

TRANSLATING TENDENCY—The tendency of the single-rotor heli-copter to move laterally during hover-ing flight. Also called tail rotor drift.

G-5

TRANSLATIONAL LIFT—Theadditional lift obtained when enteringforward flight, due to the increasedefficiency of the rotor system.

T R A N S V E R S E - F L O WEFFECT—A condition of increaseddrag and decreased lift in the aft por-tion of the rotor disc caused by the airhaving a greater induced velocity andangle in the aft portion of the disc.

TRUE ALTITUDE—The actualheight of an object above mean sealevel.

TURBOSHAFT ENGINE—A tur-bine engine transmitting powerthrough a shaft as would be found in aturbine helicopter.

TWIST GRIP—The power controlon the end of the collective control.

UNDERSLUNG—A rotor hub thatrotates below the top of the mast, ason semirigid rotor systems.

UNLOADED ROTOR—The state ofa rotor when rotor force has beenremoved, or when the rotor is operatingunder a low or negative G condition.

USEFUL LOAD—The differencebetween the gross weight and thebasic empty weight. It includes theflight crew, usable fuel, drainable oil,if applicable, and payload.

VARIATION—The angular differ-ence between true north and magneticnorth; indicated on charts by isogoniclines.

VERTICAL VIBRATION—A vibra-tion in which the movement is up anddown, or vertical, as in an out-of-trackcondition.

VORTEX RING STATE—A tran-sient condition of downward flight(descending through air after just pre-viously being accelerated downwardby the rotor) during which an appre-ciable portion of the main rotor sys-tem is being forced to operate atangles of attack above maximum.Blade stall starts near the hub and pro-gresses outward as the rate of descentincreases.

WEIGHT—One of the four mainforces acting on a rotorcraft.Equivalent to the actual weight of therotorcraft. It acts downward towardthe center of the earth.

YAW—The movement of a rotorcraftabout its vertical axis.

G-6

I-1

ABORTED TAKEOFF, GYROPLANE 21-1ACCELERATE/STOP DISTANCE 21-1AERODYNAMICS 2-1, 3-1, 16-1

autorotation, 3-8forward flight, 3-5general, 2-1gyroplane, 16-1helicopter, 3-1hovering flight, 3-1rearward flight, 3-8sideward flight, 3-8turning flight, 3-8vertical flight, 3-4, 16-1

AERONAUTICAL DECISION MAKING (ADM) 14-1, 22-1decision-making process, 14-3definitions, 14-2error chain, 14-1factors affecting decision making, 14-5hazardous attitudes, 14-6, 22-1operational pitfalls, 14-8origin, 14-2pilot error, 14-1risk management, 14-4situational awareness, 14-8stress management, 14-6use of resources, 14-6workload management, 14-7

AGONIC LINE 12-5AIRCRAFT LIGHTING 13-3AIRFOIL 2-1

angle of attack, 2-2camber, 2-2center of pressure, 2-1chord line, 2-2leading edge, 2-2pitch angle, 2-2relative wind, 2-2resultant relative wind, 3-6rotational relative wind, 3-6span, 2-1trailing edge, 2-2twist, 2-1

AIRSPEED INDICATOR 12-1, 18-4AIR TAXI 9-9AIRWORTHINESS DIRECTIVE 6-4ALTIMETER 12-2, 18-4ANGLE OF ATTACK 2-2ANTI-ICING SYSTEMS 5-11ANTITORQUE PEDALS 4-3ANTITORQUE SYSTEM FAILURE 11-11ANTITORQUE SYSTEMS 1-2

tail rotor, 1-2fenestron, 1-2NOTAR®, 1-2

APPROACHESconfined area, 10-7crosswind, 9-20night, 13-5

normal to a hover, 9-19normal to the surface, 9-20pinnacle, 10-8shallow approach, 10-5steep, 10-4

ARM 7-4ASYMMETRICAL AIRFOIL 2-1ATTITUDE INDICATOR 12-3ATTITUDE INSTRUMENT FLYING 12-1AUTOKINESIS 13-3AUTOPILOT 5-10AUTOROTATION 11-1

aerodynamics, 3-8, 16-1during instrument flight, 12-19from a hover, 11-4power recovery, 11-3straight-in, 11-2with turn, 11-3

AXIS OF ROTATION 2-2

BASIC EMPTY WEIGHT 7-1BERNOULLI’S PRINCIPLE 2-3BLADE

coning, 3-2driven region, 3-9, 16-2driving region, 3-9, 16-2feather, 1-1flap, 1-1, 16-6, 20-1lead/lag, 1-1reverse flow, 16-3stall, 11-10stall region, 3-9, 16-2

BLOWBACK 3-8BUNTOVER 21-3

CARBURETOR 5-7heat, 5-8ice, 5-7

CENTER OF GRAVITY 7-2aft CG, 7-2forward CG, 7-2lateral, 7-3, 7-7

CENTER OF PRESSURE 2-1, 16-5CENTRIFUGAL FORCE 3-2, 3-8CENTRIPETAL FORCE 3-8CLUTCH

belt drive, 5-4centrifugal, 5-4freewheeling unit, 5-4sprag, 5-4

COANDA EFFECT 1-3COCKPIT MANAGEMENT 20-1COLLECTIVE CONTROL, GYROPLANE 17-2COLLECTIVE PITCH CONTROL 4-1

INDEX

A

B

C

I-2

COLLECTIVE PITCH/THROTTLE COORDINATION 4-2COMPASS CORRECTION CARD 12-5COMPASS DEVIATION 12-5COMPASS ERRORS 12-4COMPASS TURNS 12-17CONFINED AREA OPERATIONS

approach, 10-7takeoff, 10-8

CONING 3-2CONING ANGLE 18-1CORIOLIS EFFECT 3-2CORRELATOR/GOVERNOR 4-2CREW RESOURCE MANAGEMENT 14-2CYCLIC CONTROL, GYROPLANE 17-1CYCLIC PITCH CONTROL 4-2

DATUM 7-3DECISION-MAKING PROCESS 14-3DENSITY ALTITUDE 8-1, 20-5DIRECT CONTROL 15-2DISC LOADING 2-4DISSYMMETRY OF LIFT 3-6, 16-3, 20-1DIVERSION 11-15DRAG 2-5

form, 2-5induced, 2-5parasite, 2-6profile, 2-5rotor, 16-4skin friction, 2-5total, 2-6

DUAL ROTOR SYSTEM 1-1DYNAMIC ROLLOVER 11-7

EFFECTIVE TRANSLATIONAL LIFT 3-5ELECTRICAL SYSTEMS 5-8EMERGENCIES

aborted takeoff, 21-1approach and landing, 21-3autorotation, 11-1buntover, 21-3dynamic rollover, 11-7ground resonance, 11-7, 21-3instrument flight, 12-18lift-off at low airspeeds and high angles of attack, 21-1lost procedures, 11-16low G conditions, 11-10low rotor r.p.m. and blade stall, 11-10mast bumping, 11-10pilot-induced oscillation, 21-2power pushover, 21-3retreating blade stall, 11-6settling with power, 11-5systems malfunction, 11-11vortex ring state, 11-5

EMERGENCY EQUIPMENTAND SURVIVAL GEAR 11-16, 21-4ENGINE

reciprocating, 5-1, 18-1

turbine, 5-1ENGINE INSTRUMENTS 18-3ENGINE STARTING PROCEDURE 9-2, 20-1ENVIRONMENTAL SYSTEMS 5-10EYE 13-1

cones, 13-1rods, 13-2

FALSE HORIZON 13-3FENESTRON TAIL ROTOR 1-2FLIGHT AT SLOW AIRSPEEDS 20-12FLIGHT CONTROLS 1-3, 4-1

antitorque pedals, 4-3collective pitch, 4-1, 17-2cyclic pitch, 4-2, 17-1rudder, 17-2swash plate assembly, 5-5throttle, 4-1, 17-1

FLIGHT DIVERSION 11-15FLIGHT INSTRUMENTS 12-1

airspeed indicator, 12-1, 18-4altimeter, 12-2, 18-4attitude indicator, 12-3heading indicator, 12-3magnetic compass, 12-4turn-indicators, 12-4vertical speed indicator, 12-2

FLIGHT MANUAL (See rotorcraft flight manual)FORCES IN A TURN 3-8FOUR FORCES

drag, 2-5, 16-4lift, 2-3, 16-4thrust, 2-5, 16-4weight, 2-4

FREEWHEELING UNIT 5-4FUEL INJECTION 5-8FUEL SYSTEMS 5-6FULLY ARTICULATED ROTOR 1-1, 5-4, 18-1

GO-AROUND 9-20, 20-15GOVERNOR 4-2

failure, 11-14GROSS WEIGHT 7-1GROUND EFFECT 3-3GROUND HANDLING 18-4GROUND REFERENCE MANEUVERS 9-14, 20-8

rectangular course, 9-14, 20-8s-turns, 9-16, 20-10turns around a point, 9-17, 20-11

GROUND RESONANCE 11-7, 21-3GYROPLANE

components, 15-2instruments, 18-3stability, 16-5types, 15-1

GYROSCOPIC INSTRUMENTS 12-3attitude indicator, 12-3heading indicator, 12-3

D

E

F

G

turn indicators, 12-4GYROSCOPIC PRECESSION 3-4

HANG TEST 19-4HAZARDOUS ATTITUDES 14-5

anti-authority, 14-6, 22-3impulsivity, 14-6, 22-1invulnerability, 14-6, 22-1macho, 14-6, 22-2resignation, 14-6, 22-2

HEADING INDICATOR 12-3HEIGHT/VELOCITY DIAGRAM 11-4, 19-3HELICOPTER SYSTEMS 5-1

anti-icing, 5-11autopilot, 5-10carburetor, 5-7clutch, 5-4electrical, 5-8engine, 5-1environmental, 5-10flight control, 4-1fuel, 5-6hydraulics, 5-9main rotor, 5-4pitot-static, 12-1stability augmentation system, 5-10swash plate assembly, 5-5tail rotor drive, 5-3transmission, 5-3

HIGH RATE OF DESCENT 20-12HINGES 5-5HOVERING

aerodynamics, 3-1flight, 9-5

HOVERING OPERATIONSautorotation, 11-4forward flight, 9-7rearward flight, 9-8sideward flight, 9-7turn, 9-6vertical takeoff, 9-5

HOVER TAXI 9-9HUMAN FACTORS 14-1HYDRAULIC FAILURE 11-14

INDUCED DRAG 2-5INDUCED FLOW 3-6INSTRUMENT CROSS-CHECK 12-5INSTRUMENT FLIGHT 12-5

aircraft control, 12-7bank control, 12-9emergencies, 12-18straight-and-level flight, 12-7straight climbs, 12-11straight descents, 12-14takeoff, 12-19turns, 12-15

unusual attitudes, 12-18INSTRUMENT INTERPRETATION 12-6INSTRUMENT TURNS 12-15

30° bank turn, 12-17 climbing and descending turns, 12-17compass turns, 12-17timed turns, 12-16turns to a predetermined heading, 12-16

ISOGONIC LINES 12-5

LANDINGcrosswind, 9-11, 20-14high-altitude, 20-14illusions, 13-4night, 13-5normal, 20-13running/roll-on, 10-5short-field, 20-13slope, 10-6soft-field, 20-14

LANDING GEAR 1-2, 15-3, 18-4LAW OF CONSERVATION OF ANGULAR MOMENTUM 3-2L/DMAX 2-6

LIFT 2-3, 16-4Bernoulli’s Principle, 2-3magnus effect, 2-3Newton’s Third Law of Motion, 2-4

LIFT-OFF AT LOW AIRSPEED AND HIGH ANGLE OFATTACK 21-1LIFT-TO-DRAG RATIO 2-6LOAD FACTOR 2-4LOSS OF TAIL ROTOR EFFECTIVENESS 11-12LOST PROCEDURES 11-16LOW G CONDITIONS 11-10LOW ROTOR RPM 11-10LTE (See loss of tail rotor effectiveness)

MAGNETIC COMPASS 12-4acceleration/deceleration error, 12-5compass correction card, 12-5magnetic deviation, 12-5magnetic dip, 12-5turning error, 12-5variation, 12-4

MAGNUS EFFECT 2-3MAIN ROTOR SYSTEM 1-1, 5-4

combination, 5-5fully articulated, 1-1, 5-4rigid, 1-2, 5-5semirigid, 1-2, 5-5

MANEUVERS 9-1, 10-1, 20-1after landing and securing, 9-20, 20-15approaches, 9-19climb, 9-13, 20-6confined area operations, 10-7crosswind landing, 9-20, 20-14

I

L

M

I-3

H

I-4

crosswind takeoff, 9-11, 20-4descent, 9-14, 20-6engine start, 9-2, 20-1flight at slow airspeeds, 20-12go-around, 9-20, 20-15ground reference maneuvers, 9-14, 20-8high-altitude landing, 20-14high-altitude takeoff, 20-4high rate of descent, 20-12hovering, 9-5jump takeoff, 20-5maximum performance takeoff, 10-2normal landing, 20-13normal takeoff, 20-3pinnacle operations, 10-8preflight, 9-1, 20-1prerotation, 20-2quick stop, 10-3rapid deceleration, 10-3ridgeline operations, 10-8rotor engagement, 9-2running/rolling landing, 10-5running/rolling takeoff, 10-2shallow approach, 10-5short-field landing, 20-13short-field takeoff, 20-4slope operations, 10-6soft-field landing, 20-14soft-field takeoff, 20-5steep approach, 10-4straight-and-level flight, 9-12, 20-6takeoff from a hover, 9-10takeoff from the surface, 9-11taxiing, 9-8, 20-1traffic patterns, 9-18turns, 9-12, 20-7vertical takeoff, 9-5

MAST BUMPING 11-10MAXIMUM GROSS WEIGHT 7-1MAXIMUM PERFORMANCE TAKEOFF 10-2MEL (See minimum equipment list)MINIMUM EQUIPMENT LIST 9-1MOMENT 7-4

NEVER EXCEED SPEED (VNE) 3-7, 6-2

NEWTON’S THIRD LAW OF MOTION 2-4NIGHT APPROACH 13-5NIGHT FLIGHT 13-4

approach, 13-5collision avoidance, 13-5engine starting and rotor engagement, 13-4en route procedures, 13-5landing, 13-5preflight, 13-4takeoff, 13-4taxi technique, 13-4

NIGHT MYOPIA 13-3NIGHT OPERATIONS 13-1NIGHT PHYSIOLOGY 13-1NIGHT SCANNING 13-2

NIGHT VISION 13-2NOISE ABATEMENT PROCEDURES 9-20NO TAIL ROTOR 1-2

OPERATIONAL PITFALLS 14-8

PARASITE DRAG 2-6PAYLOAD 1-1, 7-1PENDULAR ACTION 3-2, 16-5PERFORMANCE CHARTS 8-3, 19-2

climb, 8-5hovering, 8-3takeoff, 8-5

PERFORMANCE FACTORS 8-1altitude, 8-2atmospheric pressure, 8-1density altitude, 8-1humidity, 8-2temperature, 8-2weight, 8-2winds, 8-2

PILOT ERROR 14-1PILOT-INDUCED OSCILLATION (PIO) 21-2PINNACLE OPERATIONS

approach, 10-8landing, 10-8takeoff, 10-9

PITCH, AIRCRAFT 2-2PITCH HORN 5-4PITOT-STATIC INSTRUMENTS 12-1

airspeed indicator, 12-1, 18-4altimeter, 12-2, 18-4errors, 12-2vertical speed indicator (VSI), 12-2

PLACARDS 6-3POH (See rotorcraft flight manual)POWERPLANT 1-3, 15-2POWER PUSHOVER 21-3PREFLIGHT INSPECTION 9-1, 20-1

night, 13-4PREROTATE 15-2, 18-2, 20-2PREROTATOR 18-2

electrical, 18-3hydraulic, 18-2mechanical, 18-2tip jets, 18-3

PRESSURE ALTITUDE, 8-1PROFILE DRAG 2-5PROPELLER THRUST LINE 16-5

QUICK STOP 10-3

P

Q

N

O

I-5

RAPID DECELERATION 10-3RECIPROCATING ENGINE 5-1RECONNAISSANCE PROCEDURES

ground, 10-1high, 10-1low, 10-1

RECTANGULAR COURSE 9-14, 20-8REFERENCE DATUM 7-3RELATIVE WIND 2-2RESULTANT RELATIVE WIND 3-6RETREATING BLADE STALL 11-6, 16-3REVERSE FLOW 16-3RIGID ROTOR 1-2, 5-5RISK ELEMENTS 14-4RISK MANAGEMENT 14-4ROLL, AIRCRAFT 2-2ROTATIONAL RELATIVE WIND 3-6ROTORCRAFT FLIGHT MANUAL 6-1, 19-1

aircraft systems and description, 6-4emergency procedures, 6-3, 19-3general information, 6-1gyroplane, 19-1handling, servicing, and maintenance, 6-4helicopter, 6-1normal procedures, 6-3operating limitations, 6-1performance, 6-3, 19-2safety and operational tips, 6-4supplements, 6-4weight and balance, 6-4, 19-1

ROTOR DRAG 16-4ROTOR ENGAGEMENT 9-2ROTOR FORCE 16-3ROTOR LIFT 16-4ROTOR SAFETY 9-2ROTOR SYSTEMS 5-4, 18-1

combination, 5-5fully articulated, 1-2, 5-4, 18-1semirigid, 1-2, 5-5, 18-1rigid, 1-2, 5-5

RUDDER 17-2

SAFETY CONSIDERATIONS 9-2SEMIRIGID ROTOR SYSTEM 1-2, 5-5, 18-1SETTLING WITH POWER 11-5SITUATIONAL AWARENESS 14-8SKID 9-13, 20-7SKIN FRICTION DRAG 2-5SLIP 9-13, 20-7SLIP/SKID INDICATOR 12-4, 18-4SLOPE OPERATIONS

landing, 10-6takeoff, 10-6

STABILITY AUGMENTATION SYSTEM (SAS) 5-10STABILITY, GYROPLANE 16-5

center of pressure, 16-5fuselage drag, 16-5

horizontal stabilizer, 16-5pitch inertia, 16-5propeller thrust line, 16-5rotor force, 16-6trimmed condition, 16-6

STANDARD ATMOSPHERE 8-1STANDARD-RATE TURN 12-4STARTING PROCEDURE 9-2STATIC STOPS 5-5STEADY-STATE FLIGHT 2-4STEEP TURNS 20-8STRESS MANAGEMENT 14-6S-TURNS 9-16, 20-10SWASH PLATE ASSEMBLY 5-5SYMMETRICAL AIRFOIL 2-1SYSTEM MALFUNCTIONS 11-11

antitorque, 11-11governor, 11-14hydraulic, 11-14main drive shaft, 11-14

TACHOMETER 5-3, 18-3TAIL ROTOR 1-2, 5-3TAIL ROTOR FAILURE 11-11TAIL SURFACES 15-2TAKEOFF

confined area, 10-8crosswind, 9-11, 20-4from a hover, 9-10from the surface, 9-11high altitude, 20-4jump, 20-5maximum performance, 10-2night, 13-4normal, 20-3pinnacle, 10-9running/rolling, 10-2short-field, 20-4slope, 10-6soft-field, 20-5to a hover, 9-5

TAXIING 9-8, 20-1air, 9-9hover, 9-9night, 13-4surface, 9-9

TEETER BOLT 18-1TEETERING HINGE 5-5THROTTLE 4-1, 17-1THRUST 2-5, 16-4TIP JETS 18-3TIP-PATH PLANE 2-2, 9-5TIP SPEED 3-7, 16-1TORQUE 1-1, 3-1TOTAL DRAG 2-6TOWER BLOCK 18-1TOWER PLATE 18-1TRAFFIC PATTERNS 9-18TRANSLATING TENDENCY 3-1TRANSLATIONAL LIFT 3-5

R

S

T

I-6

TRANSMISSION 5-3TRANSVERSE FLOW EFFECT 3-6TRUE ALTITUDE 8-1TURBINE ENGINE 5-1TURN COORDINATOR 12-4TURN-AND-SLIP INDICATOR 12-4TURNS 9-12, 12-15, 20-7

aerodynamics, 3-8TURNS AROUND A POINT 9-17, 20-11

UNANTICIPATED YAW 11-12UNDERSLING ROTOR 3-3, 18-1UNLOADED ROTOR 21-3UNUSUAL ATTITUDES 12-18USEFUL LOAD 7-1

VENTURI EFFECT 2-3VERTICAL SPEED INDICATOR (VSI) 12-2VIBRATIONS 11-14

low frequency, 11-15medium and high frequency, 11-15

VISION IN FLIGHT 13-1night, 13-2

VISUAL ILLUSIONS 13-3autokinesis, 13-3false horizon, 13-3landing, 13-4night myopia, 13-3

VNE (See never exceed speed)

VORTEX RING STATE 11-5VSI 12-2VX 20-3

VY 20-3

WEIGHT 2-4, 7-1limitations, 7-1

WEIGHT AND BALANCE 7-1, 19-1definitions, 7-1, 7-3, 7-4

WEIGHT AND BALANCE METHODS 7-4combination method, 7-6computational method, 7-4loading-chart method, 7-5

WINGS 15-3WORKLOAD MANAGEMENT 14-7

YAW, AIRCRAFT 2-5

V

WU

Y