AE 1350Lecture #2

TOPICS ALREADY COVERED

• We reviewed the history of aeronautics and rocketry.

• We discussed the parts of the airplane.

• We discussed various ways an aircraft is graphically represented.

VARIOUS DISCIPLINES

Aerodynamics &Performance

Stability & Control

Propulsion

Structures

Design

Axes of an Airplane

Roll of an Airplane

• The longitudinal axis extends lengthwise through the fuselage from the nose to the tail.

• Movement of the airplane around the longitudinal axis is known as roll and is controlled by movement of the ailerons.

Yaw

• The vertical or normal axis passes vertically through the center of gravity.

• Movement of the airplane around the vertical axis is yaw.

• Yaw is controlled by movement of the rudder.

PITCH

• The lateral axis extends crosswise from wingtip to wing tip.

• Movement of the airplane around the lateral axis is known as pitch.

• Pitch is controlled by movement of the elevators.

AERODYNAMIC CONTROL SURFACES

• Elevators control pitch angle• Ailerons control roll angle• Rudder controls yaw angle• Flaps increase lift and drag• Leading edge slats increase lift• Drag brakes increase drag• Spoilers reduce lift.• Canard is a horizontal control surface placed near the

nose.

TOPICS TO BE COVERED

• Roadmap of Disciplines

• “English” to “S.I.” units

• Common Aerospace Terminology

• Preliminary Thoughts on Aerospace Design

• Specifications (“Specs”) and Standards

• System Integration

AEROSPACE ENGINEERINGDISCIPLINES

• Design, modeling, and testing aerospace vehicles requires knowledge and training in the areas of– Aerodynamics

– Structures

– Flight Mechanics, Stability & Control

– Propulsion

– Performance

– Design - An integration of these disciplinesto come up with a new product or concept

ENGLISH UNITS

• U. S. aerospace industries use this convention.– mass : lbm or in slugs

– Distance : feet

– Time: seconds

– Force: lbf (pronounced pound force)

– Pressure: psi (pounds per square inch), or in atm

– energy: Btu (British thermal units)

– Power: HP

– Temperature: Fahrenheit or degree Rankine ( R)

S. I. UNITSSystème International d’Unites

• Most other European and Asian nations use this.– mass - kg

– Distance - m (pronounced meters)

– Time - seconds

– Force - N (pronounced Newtons)

– Pressure - N/m2, or in atm

– energy in Joules

– Power in Watts (Joule/sec)

– Temperature in Celsius or degree Kelvin ( K)

English Units (Continued)

• Note:– 1 slug = 32.2 lbm

– 1 atm = 14.7 psi (14.7 pounds per square inch)– 0 Degrees F = 460 Degrees Rankine– We convert Fahrenheit to Rankine by adding

460 to F– 1 BTU = 778.15760 ft lb– 1 HP = 550 ft.lb/s

CONVERSION FACTORS• 1 ft = 0.3048 m• 1 slug = 14.594 kg

• 1 slug = 32.2 lbm

• 1 lbm = 0.4536 kg

• 1 lb = 4.448 N• 1 atm = 114.7 psi = 2116 lb/ft2 = 1.01 x 105 N/m2

• 1degree K = 1.8 degree R• Convert Celsius to Kelvin by adding 273 to Celsius• 1HP = 745.69987 Watts• g = Acceleration due to gravity = 32.2 ft/s2 = 9.8 m/s2

Examples• Wright Flyer weighed 340 kg

– Its weight in English Units:

• Its wing area was 46.5 m2

– The area in English units:

– Its speed = 56 km/h = 35mph (VFY: verify for yourself, please!)

mm lblb

kg 750slug 1

2.32

kg 14.594

slug 1340

22

2 5003048.0

15.46 ft

m

ftm

AEROSPACE TERMINOLOGY• GW=Gross Weight= The nominal weight for a standard mission

before the aircraft (or spacecraft) takes off.

• Crew Weight: Weight of crew and associated equipment (parachute, oxygen, etc.)

• P/L= Payload Weight = Weight the aircraft was designed to carry. (passengers weight, baggage for aircraft;satellites, imaging equipment etc. for spacecraft)

• Fuel/Weight: That required to do the mission plus required reserves

• Empty Weight = What the aircraft or spacecraft weighs when it is nominally empty (may include trapped fuel )

• GW = Crew weight+ P/L + Fuel Weight + Empty Weight

AEROSPACE TERMINOLOGY– Wing Loading = Aircraft Weight/Wing Area

– Power Loading = Aircraft Weight/ Nominal Engine Power

– Aspect ratio, AR = (Wing Span)2 / Wing Area

– Taper ratio = Root Chord/ Tip Chord

– Specific Fuel Consumption, sfc = (Fuel Weight)/ (Power x Hour)

– Empty Weight Fraction = Empty Weight/ Gross Weight

– Payload Fraction = Payload Weight/ Gross Weight

22

,m

N

ft

lb

Watt

N

HP

lb,

TYPICAL WING LOADING

• Light Civil Aircraft: 10 to 30 lb/ft2

• High Altitude Fighter 30 to 60 lb/ft2

• Interceptor Fighter 120 to 350 lb/ft2

• Long Range Transport 110 to 140 lb/ft2

PRELIMINARY THOUGHTS ON DESIGN• Design is, in general,

– a team effort– a large system integration activity– done in three stages– iterative– creative, knowledge based.

• The three stages are:– Conceptual design– Preliminary design– Detailed design

Conceptual Design

• What will it do?

• How will it do it?

• What is the general arrangement of parts?

• The end result of conceptual design is an artist’s or engineer’s conception of the vehicle/product.

• Example: Clay model of an automobile.

Conceptual Designs

Dan Raymer sketch

Conceptual Designs

1988 Lockheed Design

Preliminary Design

• How big will it be?

• How much will it weigh?

• What engines will it use?

• How much fuel or propellent will it use?

• How much will it cost?

• This is what you will do in this course.

Preliminary Design AnalysisWing sizing spreadsheetWritten by Neal Willford 12/29/03 for Sport AviationBased on methods presented in "Technical Aerodynamics" by K.D. Wood, "Engineering Aerodynamics" by W.S. Diehl, and "Airplane Performance, Stability and Control" by Perkins and HageThis spreadsheet is for educational purposes only and may contain errors. Any attempt to use the results for actual design purposes are done at the user's own risk.Input required in yellow cells

Wing area sizingA/C weight: 1150 lbs Flaps up Clmax: 1.42 get from Airplane CL page Background calculationsDesired stall speed: 45 knots, flaps up Flaps down Clmax: 1.78 get from Airplane CL page Cdo =Desired stall speed: 39 knots, flaps down Lp =

Lt =Minimum wing area needed to meet the flaps up and flaps down stall speed requirements. Use the larger of the two areas Ls =Min. Wing Area = 125.3 sq ft, to meet desired flaps down stall speed lambda =Min. Wing Area = 118.0 sq ft, to meet desired flaps up stall speed Wing AR =

Lt cnsspd =Wing span sizing. Choose span to obtain desired rate of climb and ceiling lamda cnsspd=Flat plate area: 4.00 sq ft Cs 3bl =Total wing area: 122.4 sq ft L/Dmax =Wingspan: 35.5 ft (upper wingspan for a biplane or wingspan for a monoplane)estimated k1 = 1.00 biplane span factor Prop/body int=Lower wingspan: 0 ft (lower wingspan for a biplane. Enter 0 for a monoplane) Propeller advance ratio, J =Wing gap: 0 ft (distance between upper and lower wing if the a/c is a biplane. Enter 0 for a monoplane) T (fixed pitch)=max fus width: 3.5 feet est airplane 'e'= 0.72 Oswald factor Tc (fixed pitch)=Max horsepower: 79 bhp Max prop RPM: 2422.907489 T (constant speed)=Prop W.R.: 0.066 chord/Diameter @ 75% prop radius Tc (constant speed)=Peak Efficiency 2 Blade Prop Dia. = 66 inches Peak Efficiency Pitch = 63 inches R =Propeller Diameter: 63 inches mu = 0.03 .03 concrete, .05 short grass, 0.1 long grass Dc =Est Prop efficiency= 0.75 Vto/Vstall 1.15 ratio of takeoff speed to stall speed (1.15 to 1.2) Xt fixed pitch=Prop efficiency: 0.75 ** iterate until equals estimated prop efficiency (then subtract .03 if using a wooden propeller) Ht fixed pitch=

Xt constant speed=Estimated sea level standard day performance Ht constant speed=Vmax = 127 mph = 110 knots Fixed Pitch Propeller Performance T.O. Speed=V best ROC = 72 mph = 63 knots max ROC = 902 fpmVmax L/D = 65 mph = 56 knots Abs. Ceiling = 20557 feetV min pwr = 49 mph = 43 knots Service Ceiling= 18277 feetVstall, clean = 50.9 mph = 44.2 knots Constant Speed Propeller PerformanceVstall, flaps = 45.4 mph = 39.4 knots max ROC = 1133 fpmWing loading= 9.4 lbs/sq ft Abs. Ceiling = 22899 feetPower loading = 14.6 lbs/horsepower Service Ceiling= 20878 feet

Estimated takeoff and landing performanceFixed Pitch Prop Constant Speed PropT.O. distance = 609 feet T.O. distance = 414 feetT.O. over 50' = 929 feet T.O. over 50' = 686 feetLanding distance ground roll = 420 feet, flaps down (1.15xVstall)Landing over 50' obstacle = 1023 feet, flaps down (1.15xVstall)

Estimated power off sink rate (based on method in the March 1990 issue of Sport Aviation)windmilling e: 0.48 APPROXIMATELY 2/3 of power on 'e'min sink speed = 47 knots = 54 mphsink rate = 506 ft/min

www.aero-siam.com/S405-WingDesign.xls

Detailed Design

• How many parts will it have?

• What shape will they be?

• What materials?

• How will it be made?

• How will the parts be joined?

• How will technology advancements (e.g. lightweight material, advanced airfoils, improved engines, etc.) impact the design?

Detailed Design

Dassault Systems - CATIA

Detailed Design

Dassault Systems - CATIA

Detailed Design

Dassault Systems - CATIA

A380 Arrangement

SPECIFICATION AND STANDARDS

• The designer needs to satisfy– Customer who will buy and operate the vehicle

(e.g. Delta, TWA)– Government Regulators (U.S. , Military,

European, Japanese…)

CUSTOMER SPECIFICATIONS• Performance:

– Payload weight and volume

– how far and how fast it is to be carried

– how long and at what altitude

– passenger comfort

– flight instruments, ground and flight handling qualities

• Cost

• Prince of system and spares, useful life, maintenance hours per flight hour

• Firm order of units, options, Delivery schedule, payment schedule

TYPICAL GOVERNMENT STANDARDS

• Civil– FAA Civil Aviation Regulations define such things as

required strength, acoustics, effluents, reliability, take-off and landing performance, emergency egress time.

• Military– May play a dual role as customer and regulator

– MIL SPECS (Military specifications)

– May set minimum standards for Mission turn-around time, strength, stability, speed-altitude-maneuver capability, detectability, vulnerability

SYSTEM INTEGRATION

• Aircraft/Spacecraft Design often involves integrating parts, large and small, made by other vendors, into an airframe or spaceframe (also called “the bus.”)

• Parts include– engines, landing gear, shock absorbers, wheels, brakes,

tires– avionics (radios, antennae, flight control computers)– cockpit instruments, actuators that move control surfaces,

retract landing gears, etc...

A380 Production

AEROSPACE DESIGN INVOLVES

• Lot of Analyses

• Ground testing and simulation (e.g. wind tunnel tests of model aircraft, flight simulation, drop tests, full scale mock-up, fatigue tests)

• Flight tests