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FS XXI Maneuvering Flight and Power Management

C Co. 1-212 Aviation Regiment Lowe Army Airfield

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Terminal Learning Objective: At the completion of this lesson the student will be able to discuss and apply the concepts of maneuvering flight and power management.

Condition: As a UH-60 student pilot.

Standard: In accordance with TC 1-237 Aircrew Training Manual Utility Helicopter H-60 Series and 1-212 Aviation Regiment Handbook for Combat Maneuvering Flight and Power Management.

Safety Requirements: None

Environmental Considerations: None

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• TC 1-237 Aircrew Training Manual Utility Helicopter H-60 Series

• 1-212 Aviation Regiment Handbook for Combat Maneuvering Flight and Power Management

• FM 3-04.203 Fundamentals of Flight

• TM 1-1520-237-10 Operator’s Manual for UH-60A, UH-60L, and EH-60A Helicopters

References

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• Basic maneuvering flight aerodynamics

• Relationship of maneuvering flight versus power available

• Transient torque

• Mushing

• Retreating blade stall

• Conservation of angular momentum

• Aerodynamics ECU/DEC relationship

• High bank angle turns

• Maneuvering flight rules of thumb

• UH-60 performance characteristics

• Maneuvering flight tasks

Topics Covered

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Basic Maneuvering Flight Aerodynamics

Just as rotor performance is affected by the aircraft being in or out of ground effect, there are several aerodynamic characteristics that aviators must be aware of to successfully perform combat maneuvers.

• Transient torque• Mushing• Conservation of Angular Momentum• Retreating blade stall• High bank angle turns

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Relationship of Maneuvering Flight To Power Available

Power Available is the amount of excess power (maximum torque available or transmission limit) available above that required for straight-and-level flight. It is one of the limiting factors in maneuvering flight. As the power available margin decreases, maneuvering flight capability is decreased.

1000 24 60 193

106 110 104 0 156 24 112 100 106 80 84 42 89 76 88 760 635

6000 32 53 184

81 84 78 32 106 46 86 100 116 80 89 52 82 84 81 840 775

Maximum Torque Available: 100% 100 KIAS Cruise Torque: 42%Power Available: 58%Max Angle: 60°

Maximum Torque Available: 81% 100 KIAS Cruise Torque: 52%Power Available: 29%Max Angle: 53°

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Transient Torque

Transient torque is a phenomenon occurring when lateral cyclic is applied and is caused by aerodynamic forces. When the cyclic is displaced laterally to the left, induced drag is increased causing a temporary increase in torque. When the cyclic is displaced to the right, a reduction in induced drag causes an increase in %RMR R resulting in a temporary decrease in torque.

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Transient TorqueFive factors affect how much torque change occurs during transient torque:

• Torque transients are proportional with the amount of power applied.

• Rate of movement of the cyclic. The faster the rate of movement the higher resultant torque increase.

• Magnitude of cyclic displacement directly affects the torque transient.

• Drag is increased or decreased by the factor of velocity squared. Thus, the higher the forward airspeed, the higher the torque transient results.

• High aircraft weight increases coning, which will make transient torque more pronounced.

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MushingMushing is a temporary stall condition occurring in helicopters when rapid aft cyclic is applied at high forward airspeeds. Airflow changes result in a decrease of total lift area and rotor disc coning. Instead of induced flow downward through the rotor system, an upward flow is produced resulting in a stall condition on portions of the entire rotor system. Conditions conducive to mushing include:

• High forward airspeeds• High gross weight• High density altitude• Severity of maneuver

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Retreating Blade Stall

In forward flight, decreasing velocity of airflow on the retreating blade requires a higher angle of attack (AOA) to generate the same lift as the advancing blade. When forward airspeed increases, the no-lift areas of the retreating blade grow larger, placing an even greater demand for production of lift on the progressively smaller section of lift-producing area until the tip of the blade (area of highest AOA) stalls. Maximum angles of bank less than 60° on the PPC indicate the onset of blade stall if exceeded.

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Conservation of Angular MomentumThe value of angular momentum of a rotating body will not

change unless external forces are applied. Simply put, a rotating body will continue to rotate with the same rotational velocity until some external force is applied to change the speed of rotation. Velocity can be changed by placing the mass of the rotating body closer to or further from the axis of rotation. An excellent example of this law is the figure skater.

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An Increase of %RPM R is monitored by the ECU/DEC. The ECU/DEC schedules fuel to lower %RPM 1 & 2 causing a reduction in %RPM R.

Total aerodynamic force is also forward of the lift vector causing an increase of %RPM R.

Application of lateral or aft cyclic causes the center of gravity to move inboard causing %RPM R to increase.

%RPM R Increases

Aerodynamics ECU/DEC Relationship

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%RPM R Decreases

Application of forward cyclic causes the center of gravity to move outboard causing %RPM R to decrease.

A decrease of %RPM R is monitored by the ECU/DEC. An increase of collective will further decrease %RMR R depending on rate of collective movement. Total aerodynamic force is also aft of the lift vector causing a

decrease of %RPM R.

Aerodynamics ECU/DEC Relationship

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High Bank Angle Turns

If adequate excess engine power is available, increasing collective pitch will enable continued flight while maintaining airspeed and altitude. If sufficient excess power is not available, the result is altitude loss unless airspeed is traded (aft cyclic) to maintain altitude or altitude is traded to maintain airspeed.

Bank Angle

Increase in %TQ

Load/G Factor

0° -- 1.0

15° 3.6 1.054

30° 15.4 1.154

45° 41.4 1.414

60° 100.0 2.0

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UH-60 Performance Characteristics

To minimize transient rotor droop, avoid situations which result in rapid rotor loading from low Ng SPEED and %TRQ conditions. Initiate maneuvers with collective inputs leading or simultaneous to cyclic inputs. During approach and landing, maintain at least 15% - 20% TRQ and transient droop will be minimal as hover power is applied.

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• Every aviator that employs these techniques at the wrong place and time endangers our ability to continue this critical training. • Only train maneuvers that have a combat application. • Taking unnecessary risks when carrying a load of combat equipped infantry soldiers can be equated to a Commercial Airline Pilot showing off when carrying athletes to the Olympics. • There is no excuse - do what the mission requires.

Maneuvering Flight Rules of Thumb

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Maneuvering Flight Tasks

3005 Demonstrate/Perform Flight Characteristics at Vh-IAS

3006 Perform Maximum Bank Angle

3007 Perform Maximum Pitch Angle

3008 Perform Decelerating Turn

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Demonstrate/Perform Flight Characteristics at Vh IAS

1. Maintain entry altitude/airspeed 1000 MSL and 100 KIAS.2. Increase collective to maintain maximum torque available

or transmission limit +0 to -5%.3. Establish and maintain Vh KIAS ± 5 KIAS.4. Maintain Vh KIAS for a minimum of 30 seconds.

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Demonstrate/Perform Maximum Bank Angle

1. Maintain entry altitude/airspeed 1000 MSL and 100 KIAS.

2. Maintain maximum bank angle +0 to -5°.3. Apply cyclic in direction of turn until

maximum angle is achieved followed immediately by applying cyclic in opposite direction to maximum bank angle.

4. Observe torque increase in left turn and torque decrease in right turn.

60° AOB

60° AOB

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Demonstrate/Perform Maximum Bank Angle

1. Maintain entry altitude/airspeed 1000 MSL and 100 KIAS.

2. Maintain maximum bank angle +0 to -5°.

3. Maintain the maximum bank angle without adjusting collective position.

4. Maintain maximum bank angle throughout a minimum of 270°.

Altitude with Cyclic

60° AOB 270°

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Demonstrate/Perform Maximum Bank Angle

1. Maintain entry altitude/airspeed 1000 MSL and 100 KIAS.

2. Maintain maximum bank angle +0 to -5°.3. Adjust collective and cyclic as necessary

to maintain entry altitude and airspeed. 4. Maintain the maximum bank angle

throughout a minimum of 270 degrees.

Constant Altitude and Airspeed

60° AOB 270°

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Demonstrate/Perform Maximum Pitch Angle

1. Maintain entry altitude/airspeed 400 AGL and 100 KIAS.2. Maintain maximum pitch angle +0 to -5°.3. Smoothly apply aft cyclic until the maximum pitch up angle is

achieved. 4. Maintain the maximum pitch up angle until the airspeed decreases

to 70 KIAS.5. Adjust cyclic as necessary to level the aircraft and return to 100

KIAS.

30° Pitch 70 KIAS

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Demonstrate/Perform Maximum Pitch Angle

1. Maintain entry altitude/airspeed 2000 MSL and 100 KIAS.2. Reduce collective until torque is 5% below cruise then apply

forward cyclic until the maximum pitch down angle is achieved. 3. Maintain the maximum pitch down angle until airspeed increases to

130 KIAS. 4. Apply collective to cruise power no later than 1000 MSL.5. Apply aft cyclic to level the aircraft to prevent rotor droop. Level the

aircraft and return to 100 KIAS without descending below 400 feet AGL.

30° Pitch 130 KIAS

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Perform Decelerating Turn

1. Maintain terrain flight altitude and no lower than 50 feet AHO at cruise airspeed.

2. On downwind abeam or beyond the abeam point of the intended point of termination initiate the maneuver.

3. Apply lateral and aft cyclic until the desirable bank angle and decelerative attitude is achieved.

4. Progressively decelerate while intercepting an approach angle clear of all obstacles to the point of termination.

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• Basic maneuvering flight aerodynamics

• Relationship of maneuvering flight versus power available

• Transient torque

• Mushing

• Retreating blade stall

• Conservation of angular momentum

• Aerodynamics ECU/DEC relationship

• High bank angle turns

• Maneuvering flight rules of thumb

• UH-60 performance characteristics

• Maneuvering flight tasks

Review

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Questions?

C Co. 1-212 Aviation Regiment Lowe Army Airfield