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Technology of FlightTechnology of Flight
References:
R. G. Grant: Flight: 100 years of aviation (DK Publishing Inc., New York, 2002);
The Illustrated Guide to Aerodynamics, 2nd edition, HC Skip Smith, TAB Books,
McGraw Hill Inc., New York, 1992.
R. Wilkinson, Aircraft structures and systems, Addison Wesley Longman
Limited, 1996.
A. C. Kermode, revised by R. H. Barnard and D. R. Philpott, Mechanics of Flight,
10th edition, Addison Wesley Longman Limited, 1996.
Types of flying machinesTypes of flying machinesGliders
Microlights
and ultralightsFixed wingaircraft
Rotorcraft
(helicopters
and
gyroplanes(autogyros)
Photo:NASA
GlidersGliders
Hang gliding basic
equipment needed
glider and harness.
Control pilots
movements alter the
centre of gravity
Paragliding-more
portable, easy;
Paramotors (powered
paragliders) engine,propeller, paraglider
Reference: N. Whittall, The complete hang gliding guide,
A&C Black Publishers , 1984
Photo:www.start-flying.com MicrolightsMicrolights andand ultralightsultralightsVery light 1 or 2 seat
airplanes, usually
less stringent
licensing.
Flexwing and 3 axis
microlights
Photos: www.start-flying.com
GlidersGlidersHeavier than air
craft withoutengines
Gliding principles similar to glidinganimals
Common methods -
aero-tow, winchlaunching,
Photo: Wikipedia
Image: How stuff works
GlidingGliding--aircraftaircraftGimli glider incident, 1983 Boeing 767-200,flying from Montreal to Edmonton, run out of fuelat 12 km altitude and landed in Gimli industrialpark airport.
Air Transat Flight 236, 2001- run out of fuel
above Atlantic, landed in Azores.Hapag-Lloyd Flight 3378, 2000- Airbus A310-304, run out of fuel 20 km away from airport,landed 500 m short from the runway.
Jakarta incident, British Airways 009, 1982-Boeing 747-200, failure of all four engines due tovolcano ash, glided outside the ash cloud, andengines restarted.
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1909 Pigs can fly, Claude
Moore-Brabazon
HistoryHistory
1911, female flyers1912 plane takes off from warship
1918-quadruplane
1929
1933
Boeing 247
1933
1933
1936
1936
1945
1947
19481949
1949
1954 1954
1954
1977
1989
1989
D. Davies & M. W ines, Antique and Classic Airplanes, Osprey Publishing Limited, 1989.
B. Gunston,The worlds greatest airplanes,\Elsevier-Dutton Publishing.
Helicopters andHelicopters and autogyrosautogyros
1922, the first hoveringfor over one minute.
1923, autogyro
Modern autogyro, photo:Wikipedia
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HelicoptersHelicopters
S. Newman, The foundations of helicopter flight, Edward Arnold, 1994.
Common configuration: main
supporting rotor+single tail rotor
Photo: Kai Tak : the final decade / Robbie Shaw.
Shrewsbury, England : Airlife Publishing, 1997.
HelicoptersHelicopters--controlcontrol
Single main rotor/tail rotor
Vertical main rotor thrust
Longitudinal main rotor
tilt fore/aft
Lateral main rotor tilt
lateral
Pitch main rotor tilt
fore/aft
Roll main rotor tilt lateral
Yaw tail rotorthrust/engine torque
Twin main rotor (tandem)
Vertical main rotor thrusts(collective)
Longitudinal main rotorstilt fore/aft
Lateral main rotors tiltlateral
Pitch main rotor tilt
fore/aft; main rotor thrusts(differential)
Roll main rotor tilt lateral
Yaw differential mainrotor tilt
S. Newman, The foundations of helicopter flight, Edward Arnold, 1994.
HelicoptersHelicopterstwin main rotorstwin main rotors
Tandem aligned inlongitudinal direction, oneon each end of fuselage
Side-by-side placedlaterally, on pilons
Coaxial rotors on sameaxle
Synchropter- two axlesclose together andinclined outwards
Compound addition ofextra propulsion
S. Newman, The foundations of helicopter flight, Edward Arnold, 1994.
HelicoptersHelicopterstwin main rotorstwin main rotors
S. Newman, The foundations of helicopter flight, Edward Arnold, 1994.
AirplanesAirplanes
Photo:NASA
AirplanesAirplanes
Photo: Kai Tak : the final decade / Robbie Shaw.Shrewsbury, England : Airlife Publishing, 1997.
Flying in Hong Kong:
http://www.hkaviationclub.com.hk/
Flying in remote areas:
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Human powered flightHuman powered flight
Light eagle,prototype
aircraft, 92pounds
Researchpurposes,dynamics oflow Reynoldsnumberaircraft,aeroelasticbehavior oflight aircraft
Photo: NASA
Human powered flightHuman powered flight
19771979
Solar powered flightSolar powered flightPathfinder solararrays on upper
wing surface, 8 kWppower
Pathfinder Plus 12.5 kWp
HeliosHelios
Helios prototype- solarremotely piloted aircraft
World altitude record forpropeller-driven aircraft
of almost 97,000 feet.
Photo: NASA
Propulsion systemsPropulsion systems
Propeller propulsionPiston engine
Turboprops
Jet propulsionTurbojet
Turbofan
References:
The Illustrated Guide to Aerodynamics, 2nd edition, HC Skip Smith, TAB Books,
McGraw Hill Inc., New York, 1992.
Aircraft Structures and Systems, R. Wilkinson, Addison Wesley Longman Limited, 1996.
Mechanics of Flight, A. C. Kermode, revised by R. H. Barnard & D. R. Philpott,
10th edition, Addison Wesley Longman Limited, 1996.
PropulsionPropulsion
Choice of power plant
Small private aircraft
Powered by reciprocating (piston) engine
Large commercial transport and military
aircrafts
Predominantly propelled by turbo-jet or turbo-fanengines
Intermediate size of civil aircraft
Gas-turbine driving a propeller
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Comparison between jet and propeller for
thrust productionAdvantage of propeller propulsion
Higher efficiency at lower speed
For a propeller and a jet engines produce the same
thrust
Jet-engined aircraft is transferring energy to theslipstream faster than propeller-engined aircraft
The difference in energy transfer rate becomes less
marked as the flight speed increases
Propulsion systemsPropulsion systemsPropeller propulsion
Each part of the blade has a cross-section
similar to airfoil
Thrust is produced since the differences in
pressure between the forward and the
rearward facing surfaces of the rotating
blades
Torque converted
to thrust
PropellersProduction of thrust by rotating blades
The propeller blade is set at a positive angle of attackrelative to the resultant velocity
The resultant force of which is produced can be
resolved into forward thrust and tangential resistance
components
Trailing vortex
The rotating blades produces the trailing vortices take the
form of helical trails
Blade twist
The inner part of the blade is describing a coarser helix
than the tip
If all sections of the blade are to meet the resultant
velocity at the same effective angle of attack, the
blade will need to be twisted, so that the geometricpitch angle is greater near the hub than at the tip
Propeller efficiencyPropeller efficiency
Depends on the ratio of rotation speed to
forward speed, the curve usually given for fixed
pitch
Low pitch propeller high performance for low
forward speed and high rpm.
Variable pitch enables optimal efficiency. To
enable easy operation, modern variable pitch
propellers operate at constant speed.
Number and shape of the blades also important.
Piston enginePiston engine
Older but more complex device compared to jet
engines
Low cost, high efficiency, still popular today
Internal combustion engine
Piston enginePiston engineValve opening into cylinder, downward stroke of the pistonstarts
Fuel-air mixture is drawn in (combined in a carburator), thepiston makes upward stroke compressing the gas, andthen spark is discharged by ignition system
The burning drives the piston down and provides power tothe crankshaft, and fourth stroke upward exhaustsremaining gas through the now opened exhaust valve.
First engines liquid-cooled since aircraft were too slow forair cooling. Problem solved first in rotary engine, and thennewer designs with increased airspeeds and adequatecooling fans.
Radial arrangement high power (lots of cylinders) butalso high drag, with invention of turboprops becameunnecessary and now horizontally opposed configurationis used in reciprocating engine powered small aircraft.
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Propulsion systemsPropulsion systems
Jet propulsion
Simple concept, but special alloys andmanufacturing processes needed to withstand
high temperatures
A gas-turbine propulsion device
Compressor
is used to increase the pressure (and temperature) of
the air at inlet
Advantages of jet propulsionThere is virtually no limit of speed at which can be operatedWorks well at high altitude
The ratio of power to weight can also be very high
Jet enginesRamjet
Nozzle-shaped device, air compressed by ram effect of movingthrough the air, fuel is injected and ignited and expanded gas exhaustsat high velocity
High thrust at high speeds; must be in motion at high speed to start,300 mph at sea level.
Used in some early missiles or helicopter rotor blade tips, not commonin conventional aircraft propulsion
Pulsejet
Shutter-like check valve synchronized with pulsed injection of fuel,check valve is then shut gas bursts out of the exhaust and ram effectforces the check vave open to repeat the cycle.
Also requires high speed to start, usually launched by means ofbooster rockets, used in V-1 buzz-bombs in WWII, not used inconventional aircraft propulsion
HistoryInvented in 1930s independently by Sir Frank Whittle and Hans van Ohain
First flight for Whittle engine in 1937, Ohains engine in 1939.
Originally designed for military aircraft, small intake for low drag -> highnoise levels, inefficient.
1940, report by Theodore von Karman, that he doubted that jet enginescould ever be applied to aircraft, while K. D. Woods, aircraft designprofessor, claimed that they can never be made cheap enough forcommercial flights.
Jet engineJet engineCombustion chamber
in which fuel is injected into the high-pressure air as a f ine spray,
and burned, thereby heating the air
As the temperature rises, each kg of hot air needs to occupy a
larger volume than it did when cold, it thus rushes out of theexhaust at a higher speed than at entry
The jet normally emerges at a pressure close to the ambientatmospheric value, but high velocity
Turbine
Extracts some of the energy available in the exhaust jet in order todrive the compressor
Problem with pure turbojet engine not very efficient.
Production of thrust by a jet engine
Output thrust is only a small proportion of the total thrust
produced internally, indicating that there are very largeinternal stresses
In flight, much of the thrust is come from the pressuredistribution in the intake duct system
The overall net thrust is partly related to the air flow
around the outside of the engine
External flow produces drag
Round the leading edge (rim) of the intake, the flow
speed is high, so the pressure is low, a significantforward thrust component is produced
The aerodynamic design of the intake, ducting and
engine nacelle is thus very important
Turbofan propulsion
Fan is a propeller with a large number of blades
Producing a large amount of thrust for a given disc
area,blades are close together, each blade strongly
affects the flow around its adjacent neighbors; good
for high speeds; the flow can be compressed
gradually, creating a smaller loss of energy
Ducted fanA fan or propeller is placed in a duct or shroud
Duct
A duct can provide a means of reducing the air
speed and increasing its pressure locally
A ducted fan can reduce the speed and increase the
pressure of the flow enters the duct
By-pass or turbo-fan
engines
By-passing some of the
compressed air around the
outside of the combustion
chamber and turbine can
increases the size of the low
pressure compressor stage
The efficiency can beimproved by increasing the
mass flow rate of air whilereducing the jet speed
Bypass ratio ratio of air
passing aroundthe engine to
that passing through theengine
Higher bypass ratio, higher
efficiency, but lower maximumthrust
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High by-pass ratio turbo-fans or fan-jets
A significant proportion of the overall thrust comes
form the pressure difference across the fan blades
Advantages
Increases the turbo-fan efficiency
Less noise is producedThe shroud suppress some of the noise from the fan
Low jet speed
-> turbo-fan engine can be extremely quiet
Disadvantage
Increases the diameter of the lowest pressure stage,
hence the fan diameter
the engine size increases
For large transatlantic aircraft
Four wing mounted and ducted engines must be used
for cruising at high subsonic Mach number
For twin-enginedt ransports and for cruise Mach numbersup to 0.86
Higher-efficiency unducted designs are preferable
Reheat or afterburning
Burning more fuel in an extended tailpipe sectionGives a significant boost in thrust
AdvantagesGives additional thrust with a relatively small increase inweight
High-efficiency for supersonic flight
DisadvantagesExtremely inefficient in low speed flight
Normally only used for takeoff
The extra pipe length produces extra drag when not inuse
Thrust reversal
Thrust reversers deflect the exhaust jet forward
and provide additional breaking action
Used for shorten the landing run for jet propulsion aircraftwith no propeller
Same effect in propeller engines with pitch reversal
Can be operated safely only on he ground, inhibited inflight.
Turbo-props
A propeller is driven by the gas-turbine
Designed for low flight speed
Higher efficiency than pure turbo-jet
Most of the energy available in the exhaust gases is extracted bythe turbine, and fed to the propeller
Gearbox to reduce rpm before attachment to the propeller
Nearly all thrust comes from the propeller (85-90%), rather thandirectly from the engine as jet propulsion
Propeller has higher propulsion efficiency than jet
Advantages
High power-to-weight ratio as turbo-jet propulsion
A power output that rises with flight speed
Disadvantages
When used with a conventional propeller, it is limited to
use at Mach numbers of less than about 0.7
Large heavy and complex gearboxBecause of the high rotational speed of the turbine,
turbo-props normally use a reduction gearbox toconnect the propeller shaft to that of the turbine
-> for large engines, the gearbox becomes a very large,
heavy and complex item, reducing some of the
theoretical advantages of the system
Supercharging and turbocharging
At high altitude, less parasite drag
due to lower air density, but engine
performance is also worse
Supercharger
Consist of centrifugal compressordriven from the crankshaft
Increases the power-to-weight ratio
By pressurizing the air beingfed into the cylinders, a larger
mass of air is used in each
working stroke
Advantages
Enables an engine to operate
at higher altitude than it couldin unsupercharged form
Enables an aircraft to take offheavily laden from high
altitude airfields on hot days
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Turbocharger
Similar to supercharger
The compressor is driven by turbine, which is poweredby the residue energy in the exhaust gases
Advantages
More efficient than a plain supercharger since it
makes use of wasted heat
Disadvantages
For small aircraft flying at low altitude
-> increases of cost and complication of the engine, the
pilot has to monitor or control the boost pressure
Performance comparisonsPerformance comparisons
Low speeds (
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Takeoff performanceTakeoff performance
VTOL vertical take-
off and landing; firstpatent in 1928 to
Nicola Tesla,
prototypes in 1950s
Directional thrust
Tiltrotor (example V-22
Osprey)
Directed jet thrust
(example Harrier II)
Landing performanceLanding performance
Landing distance depends on approach and
touchdown speed, rapidity of brakingBraking action depends on local conditions;
friction coefficients- dry concrete 0.7, light rain
0.5; heavy rain 0.3; snow or ice 0.1-0.2
Flaps increase drag but also increase lift; result-
slower touchdown speed
Also affected by wind, but not by touchdown
mas
Supersonic FlightSupersonic Flight
Supersonic flowAircraft designs are totally different in flight with highspeed and low speed
Different designs of engines, wing shapes and fuselagesMost aircraft have to land and take off and must thereforebe capable of satisfactory operation at both subsonic andsupersonic speed
Speed of sound
Sound transmission- pressure disturbances in the air.Same speed of transmission for disturbances createdby airplane flying.
Depends upon the absolute air temperatureAt low altitudes, where the temperature is relatively high, thespeed of sound is higher than it is at high altitudes where the
temperature is lower
High speed flow
The flow is undisturbed until it crosses the shockwave where speed is suddenly reduced, and airpressure temperature and density, suddenly increase
Shock wave
The along which the abrupt change in speed,temperature and pressure take place
Mach numberFlight Mach number = aircraft speed
speed of sound
M 1 (supersonic flight)
Subsonic patch appears near thenose of the aircraft
Flow speed decreases andtemperature increases beyondthe shock wave near the nose,the increasing of temperaturealso increasing the sound ofspeed
Local Mach number
Change in density
The density of air reduces as the speed is increased in the large
pressure differences region
Compressible flow -> the density of the flow can be changed
Compressible flow becomes significant when Mach number is larger
than one
Strength of shock wave depends on the normal component
of the oncoming flow velocity which is perpendicular to the
shock wave curveStronger the shock wave, greater the change of velocity, pressure
and density
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Drag in supersonic flightDrag in supersonic flight Some aircraft characteristicsSome aircraft characteristics
Swept wings smaller component of forwardvelocity relevant to wings airfoil; lowerperformance at low speeds; improved lateralstability
Sharp leading edges ideal for supersonic flight,but have poor low-speed performance
Control problems vortex generators used, withconventional control surfaces shock waves canform at junction between fixed and movableparts.
Propulsion for Supersonic FlightPropulsion for Supersonic Flight
Intake designTurbo-jet and turbo-fan designs do not acceptsupersonic flow at inlet
By placing the engine in a suitably-shaped duct, itis possible to slow the air down to subsonic speedsbefore entry
The duct is designed for compressing the flow through aseries of oblique shock waves, a region of shocklesscompression and a weak normal shock
Part of the compression is provided by the shock waveproduced by the wing, this shows the importance ofintegrating the design of the engine intake with that of the
wing
Exhaust nozzle
Variable geometry nozzle is required for
supersonic aircrafts
Variable geometry nozzle can be adjusted to
produce a convergent-divergent configuration for
high-speed flight
In a convergent-divergent nozzle, the jet can beaccelerated to Mach numbers greater than 1
For subsonic aircraft the jet is normally accelerated by
means of a simple fixed converging nozzle, the jet
maximum Mach number can be obtained is 1
Supersonic aircraft invariably use reheat, which also
requires the use of a variable geometry nozzle
The designs involving a large number of moving
parts, all of which have to stand up to very high
temperatures
The complexity of the nozzle mechanism may be
reduced if a two-dimensional design is usedinstead of the conventional axi-symmetricarrangement
The variable-geometry slot can be arranged
to produce thrust vectoring for control
purposes, and short take-off and landing(STOL)
Ramjet propulsionThe simplest form of jet-propulsion
Only consist of a suitably shaped duct with acombustion chamber
When air enters the intake of a jet engine, its
speed is reduced, and the pressure risescorrespondingly
Ram compression effect means that as the aircraftspeed rises, the compressor become less and lessnecessary
At Mach number in excess of about 3, efficient propulsioncan be obtained with no compressor at all
Elimination of the compressor means that the turbineis also unnecessary
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The thrust force is produced mainly by a high
pressure acting on the interior walls of theintake
For efficient operation at high Mach numbers, a
more complicated intake geometry is required,
which is similar to the types used for thesupersonic turbo-jet propulsion
Scramjet propulsion
Operate at very high Mach numbers
Supersonic flow in the combustion chamber
Reactive chemicals or gases must be used as its fuels
Advantage
Eliminated the energy degradation in the turbine andcompressor resulting in high efficiency at high Mach numbers
Kinetic heating effects in such a high speed render
conventional aluminium alloys and construction
techniques unsuitable
Disadvantage
Inefficient below a Mach number of about 3
Other form of propulsion is required to provide the initial
acceleration to high speed
Initial booster rocket is normally used in missiles
Flight-launched from a mother aircraft is required for
ramjet-propelled aircrafts
Dual-mode turbo-ramjet
Use a turbo-jet engine inside a ramjet duct
At low speed
The engine performs as a conventional turbo-jet
At high Mach numbers
Some or all of the air may be by-passed around
the main core engine and used in an afterburner toproduce ramjet propulsion
Take-off or landing require a reasonable
subsonic performance
The wing with acceptable low speed and high
speed performance and which does not have any
violent change in flow characteristics as the aircraft
accelerates through its speed range should beemployed
Supersonic flight- mainly military aircraft
Civil supersonic aircraft Concorde no longer
in service
The ConcordeThe ConcordeUK and France startedworking separately in1956, jointly in 1962.
First flight in 1969, Mach2 achieved in 1970.
Tupolev Tu-144 the firstflight two months before
Concorde, but neverentered commercialservice. Crashed in 1973Paris airshow.
P. R. March, The Concorde Story, Sutton
Publishing Limited, 2005.
The ConcordeThe ConcordeOnly supersonic passengeraircraft
New York-London flight typically 3-3.5 hours. Record:2 h 55 min 15 s.
Droop-nose for visibilityduring take-off and landing.
Commercial flights 1976
(BA London-Bahrain, AirFrance Paris-Rio deJaneiro.
Total of 20 Concordes werebuilt.
P. R. March, The Concorde Story, Sutton
Publishing Limited, 2005.
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The ConcordeThe ConcordeAccident in 2000, crash ontake-off in Paris
Flights resumed in 2001 afterupgrades and recertification.
Last flight Oct. 2003.Commercial reasons, notechnical support from Airbus,successor of joint Anglo-French manufacturers.
P. R. March, The Concorde Story, Sutton
Publishing Limited, 2005.
The ConcordeThe ConcordeRange 6880 km
Fuel consumption 25629 l/h
Cruising speed Mach 2
Fuselage width 2.5 m
108 passengers
2 pilots, one flight engineer, 8cabin crew
Flew around the world in 29h59 min.
Tupolev Tu-144LL flyinglaboratory, joint research byNASA and Russianaerospace industries, 1996-1999.
Development of USA-builtsupersonic jetliner currentlyon hold.
P. R. March, The Concorde Story, Sutton
Publishing Limited, 2005.
Aircraft ShapesAircraft Shapes
Aircraft shapes
The overall shape of the aircraft strongly
depends on its purpose
Required cruising speed and altitude
Required stability and maneuverability
Required capacity
Aircraft partsAircraft partsThe mainplane or wing
Most important part, generates lift. Can also carry fuel, supportundercariage or weapons loads.
Flying wing only for some special purpose aircraft, remotecontrol aircraft, B2 bomber; low radar cross-section
The fuselage or bodyForms the body, housing the crew, payload, aircraft systems,forms structural link between wing and tail unit. May carry theengines, and typically has environmental control, pressurizedenvironment (2.4 km for civil, 7.6 km for military) whichgenerates tensile loads.
The tail unit (foreplanes for canard-type)Typically vertical fin with a movable rudder and horizontaltailplane with movable elevators, or an all-moving horizontaltailplane. Canard-type horizontal tail surface replaced orsupplemented with a moving control surface at the nose.
Mountings for other systems (undercarriage, engines,etc.)
Aircraft partsAircraft parts
Aircraft ShapesAircraft Shapes
R. Wilkinson, Aircraft Structures and Systems, Addison Wesley Longman Limited, 1996
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WingsWings
Biplanes
Monoplanes
Most of modern aircraft, needs stiff, strong wing, butlower drag is obtained
Braced monoplanes diagonal bracing strut betweenthe wing and fuselage, lighter structure of the wingbut extra drag.
Cantilever wing (at different positions)Low wing (jet transport, light aircraft)
High-wing (turbo-prop transport)
Low-wing or mid-wing (combat aircraft)
Speed : high speed, smaller wing span, low wingarea, high wing loading.
WingWing planformplanform
Elliptical ideal shape, the lowest drag,
expensiveTapered similar aerodynamics toelliptical
Rectangular- most economical, butheavier than necessary.
Combination of rectangular and taperedplanform.
Wingtip shapeWingtip shape
effectseffects
Tip shape affects tip
vortex induced drag
Drooped wingtip
Upswept wingtip
Hoerner wingtip
WingletsWingletsIncreased effective aspect ratioCreates lift perpendicular to theairstream
As a result, there is a forwardcomponent, negative drag orthrust
However, increases parasitedrag and interference drag
Effective where vortex action isstrong, i.e. low speeds or highaltitudes, also in STOL aircraft
Can also be used on propellertips, resulting in higher efficiencydue to lower propeller drag
SweepSweep--back, swing wings, delta wingsback, swing wings, delta wings
Swept wings reduce local Mach number, shiftaerodynamic centre closer to the centre of gravity.Problems reduced lift-to-drag ratio, increasedlikelihood of tip stalling
Swing wings changing sweep back in flight
Delta wings for fighter aircraft, high speed +ability fortight turns Swing wingsSwing wings
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Flaps, slats, spoilers, lift dumpersFlaps, slats, spoilers, lift dumpers
Flaps are fitted at trailing edges, reduce landingspeed by increasing lift and drag
Slats extend forward from the leading edge,increase the lift by increasing camber. Slot gapbetween the slat and leading edge, reducestendency to stall.
Spoilers on top surface of aircraft with goodglide and low speed performance, increase dragbut reduce lift.
Lift dumpers on top surface of larger aircraft,instant reduction of lift
TailTail
Purpose stability and control
Vertical fin+horizontal stabilizer
Twin fins+horizontal stabilizer smaller fins
T-tail horizontal surface near the top of the tail:improved spin recovery, also horizontal surfaceplaced outside downwash; problems: additionalweight, being immersed in the wake of stalledwing
V-tail single surface on either side of center linecanted upward; vertical projection provideslongitudinal stability, horizontal projectionprovides directional stability. Problem complicated control.
CanardsCanards
Advantage
additional lift, outside
downwash
Disadvantage-
destabilization at
large angle of attack
Aircraft designAircraft designConceptual design, preliminary design (mainly aerodynamic),
detail design (mainly structural)
Very complex, compromises necessary, depending on priority ofdesired design properties
Computer aided design
Aerodynamic testingAerodynamic testing
Wind tunnels
Force tests, pressure
tests, flow patterns
Flight testing
Some different designsSome different designs
Lear Fan prototype,
1981, entirely
graphite-epoxy
composite, terminateddevelopment when
funds exhausted
Beech starship, first
composite aircraft to
be certified