TheT/WandW/S(wingloading)arethetwomostimportantparametersaffectingaircraftperformance.Optimizationoftheseparametersformsamajorpartoftheanalyticaldesignactivitiesconductedafteraninitialdesignlayout.

SW

Lowlargewingenoughvolumeforlandinggearandfuel.

Highsmallwingnotenoughvolumeforlandinggearandfuel.incrementofwettedareaandadditionaldragforce

TakeoffdistanceWT

SW ,

Forshorttakeoff SW

WTlargewing,smallengine; smallerThrust

smallwing,largeengine; SW

WT higher

Thrust

It is frequentlydifficult tousehistoricaldata to independently select initialvaluesforT/WandW/S

Thedesignermustguessatoneoftheparametersandusethatguesstocalculatetheotherparameterfromthecriticaldesignrequirements.

SW

Criticaldesignrequirement;stallspeedduringtheapproachforlanding.

(Approachstallspeedisindependentofenginesize.)Then,theestimatedW/ScanbeusedtocalculatetheT/Wrequiredtoattainotherperformancedriverssuchassingleenginerateofclimb.

la

n

d

i

n

g

l

a

n

d

i

n

g

takeoff

l

a

n

d

i

n

g

ThrusttoWeightRatioThrusttoWeightDefinitions

WT

quickaccelarationrapidclimbhighermaximumspeedhigherturnrates

morefuelconsumptionhigherengineweight

constWTburningfuelW )(

),( VhTT

DesignT/WmustbemeanT/Wduringsealevel(zerovelocity),standarddayconditionsatdesigntakeoffweightandmaximumthrottlesetting.IfarequiredT/Wiscalculatedatsomeothercondition,itmustbeadjustedbacktotakeoffconditions.

PowerLoadingandHorsepowertoWeight

JetengineaircraftWT Propellerpoweredaircraftpowerloading

hpW

Powerloadingformostaircraft:1015[lb/hp]

Powerloadingforaerobaticaircraft:6[lb/hp]

EquivalentT/Wforpropelleredaircraft:

][550

unitsfpsWhp

VWP

VWT pp

StatisticalEstimationofT/W

Aircrafttype TypicalinstalledT/W

Jettrainer 0.4

Jetfighter(dogfighter)(afterburner) 0.9

Jetfighter(other) 0.6

Militarycargo/bomber 0.25

Jettransport(highervalueforfewerengines)

0.250.4

(Inmksunits,thethrustforceisfoundas(T/W)x(mass)x(g[9.807]))

AircrafttypeTypicalP/W Typicalpower

loading[lb/hp]hp/lb [watt/g]

Poweredairplane 0.04 [0.07] 25

Homebuilt 0.08 [0.13] 12

Generalaviation(singleengine) 0.07 [0.12] 14

Generalaviation(twinengine) 0.17 [0.30] 6

Agricultural 0.09 [0.15] 11

Twinturboprop 0.20 [0.33] 5

Flyingboat 0.10 [0.16] 10

Thrusttoweightratio.

Powertoweightratio.

Atmaximumpowersettingsat sealevel and zerovelocity(static)condition.

Attakeoffweights:ModernjetfighterT/W1.0Atcombatconditions(withfuelburningW):T/W>1.0 capableofaccelerating

T/W0=aMCmax a C

Jettrainer 0.488 0.728

Jetfighter(dogfighter) 0.648 0.594

Jetfighter(other) 0.514 0.141

Militarycargo/bomber 0.244 0.341

Jettransport 0.267 0.363

T/W0vsMmax

P/W0=aVCmax:hp/lbor[watt/g] a C

Sailplanepowered 0.043[0.071] 0

Homebuiltmetal/wood 0.005[0.006] 0.57

Homebuiltcomposite 0.004[0.005] 0.57

Generalaviation(singleengine) 0.025[0.036] 0.22

Generalaviation(twinengine) 0.036[0.048] 0.32

Agriculturalaircraft 0.009[0.010] 0.50

Twinturboprop 0.013[0.016] 0.50

Flyingboat 0.030[0.043] 0.23

P/W0vsVmaxKnotsor[km/hr]

Curvefit equaitons basedupon maximum Machnumberorvelocity.Thesecanbeusedforfirstestimation.

ThrustMatching

Foraircraftdesignedprimarilyforefficiencyduringcruise:AbetterinitialestimateoftherequiredT/Wcanbeobtainedbythrustmatching:Comparisonoftheselectedenginesthrustavailableduringcruisetotheestimatedaircraftdrag.

DT WL

Cruiseflightcondition:

cruisecruisecruise DLLD

WT

/1

estimatedvaluecanbeused.

Cruise

Jet 0.866(L/D)max

Propeller (L/D)max

refwet SS /

ThisT/Wisatcruisecondition.T/W,fortakeoffatsealevelcondition,mustbecalculated.

Thismethodassumesthattheaircraft iscruisingatapproximatelytheoptimumaltitude fortheasyetunknownW/S.Themethodwouldbeinvalidiftheaircraftwereforcedbythemissionrequirementstocruiseatsomeotheraltitude,suchassealevel.Whenthewing loadinghasbeenselected,theL/DattheactualcruiseconditionsshouldbecalculatedandusedtorechecktheinitialestimateforT/W.Thehighestweightduringcruiseoccursat thebeginningof thecruise.Fuelburnedduringtakeoffandclimbtocruisealtitudecanbecalculated.

Mission segmentsweightfractions

Atthebeginningofthecruise:

offtakestartcruise WW 956.0Thrustduringcruiseisdifferentfromthetakeoffvalue.Jetaircraftsaredesignedtocruiseatapproximatelyatwhichtheselectedenginehasthe lowestspecificfuelconsumption(SFC),typically10000m.WhileSFCisimprovedatthesealtitudes,thethrustdecreases.

Also, theengine issizedusing the thrustsetting thatproduces thebestSFC.This isusually70100%ofthemaximumcontinuous,nonafterburningthrust.

offtakecruise TT RequiredcruiseT/WmustbeadjustedtoobtaintheequivalenttakeoffT/W.

asubsonic,highbypassratioturbofanforatransportaircraft:alowbypassafterburningturbofanorturbojet:

2025%ofthe offtakeT

4070%ofthe offtakeT Thrustlapseatcruise.

AircraftDesign:AConceptualApproach,RaymerD.P.

Forapistonpowered,propellerdrivenaircraft,thepoweravailablevarieswiththedensityoftheairprovidedtotheintakemanifold.Iftheengineisnotsupercharged,thenthepowerfallsoffwithincreasingaltitudeaccordingtodensityratio,:Anonsuperchargedengineat3048mwillhaveabout73%ofitssealevelpower.

To prevent this powerdecrease, many pistonengines use a superchargertomaintain theairprovidedtothemanifoldatessentiallysealevel density up to thecompression limit of thesupercharger. Above thisaltitude,thepowerbeginstodropoff:Piston powered aircrafttypicallycruiseatabout75%oftakeoffpower.

Pistonenginepowervariationwithaltitude

AircraftDesign:AConceptualApproach,RaymerD.P.

With a turboprop, there is an additional, residual thrust contribution from the turbineexhaust.Itiscustomarytoconvertthisthrusttoitshorsepowerequivalentandaddittotheactualhorsepower,creatinganequivalentshafthorsepower(eshp).Foratypicallyturbopropengineinstallation,thecruiseeshpisabout6080%ofthetakeoffvalue.ThetakeoffT/Wrequiredforcruisematchingcannowbeapproximated:

cruise

offtake

offtake

cruise

cruiseofftake TT

WW

WT

WT

0.956 shouldbeobtainedfromactualenginedataifpossible.

Afteran initial layouthasbeen completed,actualaerodynamic calculationsaremade tocomparethedragduringcruisewiththethrustavailable.

T/Wisoftendeterminedbyaclimbrequirementratherthanbycruiseconditions.Commonproblem:TheT/Wforclimbcanbeso largethattheenginesmustthrottledwaybackduringcruise,andanaircraftengineisusuallyveryinefficient.Thisisespeciallytrueforjetengines.

cruisecruise DLWT

/1

T/Wforclimb:

(T/Wforlevelflight)+ (anextrathrustpowerrequiredfortheclimbgradient)

VV

DLWT vertical

mbclimbcli

/1 design

requirement

Forthefirstpassestimate,theT/W(orP/W)shouldbeselectedasthehigherofeitherthestatisticalvalueobtainedfromthetablesorthevalueobtainedfromthethrustmatching.AfterselectionofW/S,theselectedT/Wshouldberecheckedagainstallrequirements.

WingLoading

SW

stallspeedclimbratetakeoffdistancelandingdistanceturnperformancedesignliftcoefficientwettedarea,wingspandrag

SW

Takeoffgrossweight

SW

Largerwing

Performanceimprovement

DragWtakeoff

HistoricalterndsTypicaltakeoff(W/S)

lb/ft2 [kg/m2]

Sailplane 6 [30]

Homebuilt 11 [54]

Generalaviation(singleengine) 17 [83]

Generalaviation(twinengine) 26 [127]

Twinturboprop 40 [195]

Jettrainer 50 [244]

Jetfighter 70 [342]

Jettransport/bomber 120 [586](Inmksunits,thethrustforceisfoundas(T/W)x(mass)x(g[9.807]))

Wingloading

T/WandW/Smustbeoptimizedtogether.InitiallyestimationofW/Sallowthedesignertobeginthelayoutwithsomeassurancethatthedesignwillnotrequirecompleterevisionaftertheaircraftisanalyzedandsized.Toensurethatthewingprovidesenoughliftinallcircumstances,thedesignershouldselectthelowestoftheestimatedwingloadings.If an unreasonably low wing loading value is driven by only one of these performanceconditions,thedesignershouldconsideranotherwaytomeetthatcondition.Forexample,ifthewingloadingrequiredtomeetastallspeedrequirementiswellbelowallotherrequirements,itmaybebettertoequiptheaircraftwithahighliftflapsystem.Iftakeoffdistanceorrateofclimbrequireaverylowwingloading,perhapstheT/Wratioshouldbeincreased.

StallSpeed

ThestallspeedofanaircraftisdirectlydeterminedbytheW/SandcLmax.Stallspeedisamajorcontributortoflyingsafety,withasubstantialnumberoffatalaccidentseachyearduetofailuretomaintainflyingspeed.Also, theapproach speed,which is themost important factor in landingdistanceandalsocontributestoposttouchdownaccidents,isdefinedbythestallspeed.

FAR23certifiedaircrafts: W

Stallspeedflightwithmaximumliftcoefficient

LSLL ScVScVWL 22 21

21

2/1

max

)/(2

LSLstall c

SWV ?

Aplainwingwithnoflaps 1.21.5

Awingwithlargeflapsimmersedinthepropwashorjetwash 5.0

Shorttakeoffandlandingaircraft 3.0

Aregulartransportaircraftwithflapsandslats 2.4

Otheraircraftswithflapsontheinnerpartofthewing 1.62.0

ceInterferentextureSurface

numberslotedgeLeading

SpangeometryFlap

shapeAirfoilgeometryWing

fcL

Re

max

(Thetrimforceprovidedbythehorizontaltailwillincreaseorreducethemaximumlift,dependingonthedirectioofthetrimforce)

Duringlanding,theflapswillbedeployedthemaximumamounttoprovidegreatestlift.However,fortakeoffthemaximumflapanglewillprobablycausemoredragforce:Typically,thetakeoffmaximumliftcoefficientisabout80%ofthelandingvalue.

A > 5 the maximum lift coefficient of wing will be approximately 90% of the airfoilmaximumliftcoefficientatthesameReynoldsnumber.Ifpartialspanflapsareused,theirdeflectionwillintroducealarge,discontinuoustwistintothewinggeometrythatchangesthe liftdistribution,thusthe induceddownwash,causingtheeffectiveangleofattacktovaryatdifferentspanstations.

ref

unflappedunflappedl

ref

flappedflappedlL S

Sc

SS

cc )()(9.0 maxmax

The lift coefficient of the unflappedairfoil at the angleof attack atwhichtheflappedairfoilstalls.

For a better initial estimationofmaximumlift,itisnecessaryto resort to test results andhistoricaldata.

(remember:thetakeoffmaximumliftcoefficientisabout80%ofthelandingvalue)

AircraftDesign:AConceptualApproach,RaymerD.P.

TakeoffDistance

Groundrollistheactualdistancetraveledbeforethewheelsleavetheground.Theliftoffspeedforanormaltakeoffis1.1Vstall.Obstacleclearancedistance isthedistancerequiredfrombrakereleaseuntiltheaircrafthasreachedsomespecifiedaltitude.This is usually 50 ft (15.24 m) for military or small civil aircraft and 35 ft (10.7 m) forcommercialaircraft.

BalancedFieldLengthisthelengthofthefieldrequiredforsafetyintheeventofanenginefailureattheworstpossibletimeinamultiengineaircraft.Thespeedatwhichthedistancetostopafteranenginefailureexactlyequalsthedistancetocontinuethetakeoffontheremainingenginesiscalledthedecisionspeed.(V1)

W

TcgS

WS

SLLSL

LO

max

2

44.1

AircraftDesign:AConceptualApproach,RaymerD.P.

ForinitialestimationoftherequiredW/S,astatisticalapproachforestimationoftakeoffdistancecanbeused.

Thetakeoffliftcoefficientistheactualliftcoefficientattakeoff,notthemaximumliftcoefficientattakeoffconditionsasusedforstallcalculation.Theaircrafttakesoffatabout1.1Vstallsothetakeoffliftcoefficientisthe(cLmax/1.21).Required(W/S)tomeetagiventakeoffdistancerequirement:

WhpcTOP

SW

TOL)(

WTcTOP

SW

TOL)(

Propeller:Jet:

TOP

Aircraft TakeoffWeight TakeoffSpeedBoeing737 100,000lb[45,360kg] 150mph[250km/h,130kts]Boeing757240,000lb[108,860kg] 160mph[260km/h,140kts]AirbusA320 155,000lb[70,305kg] 170mph[275km/h,150kts]AirbusA340 571,000lb[259,000kg] 180mph[290km/h,155kts]Boeing747 800,000lb[362,870kg] 180mph[290km/h,155kts]Concorde 400,000lb[181,435kg] 225mph[360km/h,195kts]

Speed Description FAR25RequirementVs Stallspeedintakeoffconfiguration Vmc Minimumcontrolspeedwithoneengineinoperative(OEI) V1 OEIdecisionspeed =or>VmcVr Rotationspeed 5%>VmcVmu Minimumunstickspeedforsafeflight =or>VsVlof Liftoffspeed 10%>Vmu

5%>Vmu(OEI)V2 Takeoffclimbspeedat35ft 20%>Vs

10%>Vmc

CatapultTakeoff

Mostnavalaircraftmustbecapableofoperationfromanaircraftcarrier:Acatapultacceleratestheaircrafttoflyingspeedinaveryshortdistance.Catapultsaresteamoperated,andcanproduceamaximumforceontheaircraftdependingonthesteampressure.Therefore,alightaircraftcanbeacceleratedtoahigherspeedbythecatapultthanaheavyone.

21.1)(

21 max2 offtakeL

thrustwodendofftake

cVVV

SW

catapult windoverdeck engine

LandingDistanceLandinggroundroll is theactualdistance theaircraft travels from the timewheels firsttouchtothetimetheaircraftcomestoacompletestop.Landingfieldlengthincludesclearinga50ft(15.24m)obstaclewhiletheaircraftisstillatapproachspeedandontheapproachglidepath(normally30).Landingdistanceislargelydeterminedby(W/S).

stallapproach VV 3.1Civilaircraft:Militaryaircraft: stallapproach VV 2.1

)(180max

ftScS

WS aL

landing

)(15max

mScS

WS aL

landing

Obstacleclearencedistance

Sa

Airlinertype,30glideslope 1000ft[305m]

Generalaviationtype,poweroffapproach

600ft[183m]

STOL,70glideslope 450ft[137m]

Areasonablefirstguessofthetotallandingdistance:

][)(3.0 2 knotsVapproach

Withthrustreverser:Commercialaircraftrequiredsafetymargin:

landingS66.0

landingS67.1

ArrestedLandingAircraft that landonNavyaircraftcarriersare stoppedbyacableandbrakearrangementcalledarresteinggear.Oneofseveralcablesstrungacrosstheflightdeckiscaughtbyahookattachedtotherearoftheaircraft.Thecableisattachedatbothendstodrummechanismswhichexertadraguponthecableasitispulledbytheaircraft,thusstoppingitinaveryshortdistance.Forcarrierbasedaircraft,theapproachspeedis1.2Vstall.Carrierpilotsdonotflareandslowdownforlanding.Instead,theyaretaughttoflytheaircraftrightintothedeck,relyinguponthe arresting gear tomake the landing.By using this technique, the aircraft has enoughspeedtogoaroundifthecablesaremissed.

Thefigurecanbeusedtodeterminetheallowableapproachspeedbaseduponafirstguessofthelandingweight.Theapproachspeeddividedby1.15definesthestallspeed,whichcanthenbeusedtoestimatethewingloading.

WingLoadingforCruise

?0Dc

Jetaircraft0.015Cleanpropelleraircraft0.02Dirty,fixedgearpropelleraircraft0.03

Zeroliftdragcoefficient

?eFighteraircraft0.60.8Otheraircraft0.8Oswaldefficiencyfactor

(measureofdragduetoliftefficiency)

Tomaximizerangeduringcruise(W/S)shouldbeselected toprovideahigh(L/D)atthecruiseconditions.

Cruiseflight

Jet Propeller

0.866(L/D)max (L/D)max2/1

0

kc

cc DLL mEpropellerBR

2/1

30

kc

c DL jetBR

0WLCruiseflightqScWL L

qSWcL/

0DAecq

SW Maximumpropellerrange

3/0D

AecqSW Maximumjetrange

Aek

1

Cruiseflightfuelburnedweightreduces(W/S)Thiscanbeeqalizedq 2

21 Vq

V h; cruiseclimbflight

Airtrafficcontroldoesnotlikeaircrafttokeepgraduallyclimb:Aircraftsometimesallowedtoperformstepclimbduringcruisewithhof600mor1200m.

WingLoadingforLoiterEndurance

Loiterflight

Jet Propeller

(L/D)max 0.866(L/D)max2/1

0

kc

cc DLL mEjetBR

2/1

30

kc

c DL propellerBR

0DAecq

SW

Maximumpropellerloiter

3/0D

AecqSW

Maximumjetloiter

20minutesofloiterbeforelanding

Iftheloiteraltitudeisnotspecified: cJetaircraft:h=3000040000ft[10000m]Pistonpropeller:h=limitaltitudeforturbocharger h=sealevelfornonturbocharger

4/12/1

0

max

)/(2

DSL

tloiter ckSWVV

Forinitialdesignpurposes:Loitervelocity:150200knots[325km/h]forturbopropsandjets80120knots[180km/h]forpistonprops

Formostaircraft,thwingloadingwillbeselectedforbest cruise or other requiremenys and the loitercapabilitieswillbeasecondaryconsideration.

Intheabsenceofbetterinformation,thisratiocanbeassumedtobeabout0.85

2/12

22

)1n(gV

tangVVr

Vng

Vg 2/12 )1(tan

n,Vrmtr

TurningFlight

2/1

LSLturning,stall

maxc

)S/W(n2V

Cornerspeed:

2/1

LSL

maxcorner

maxc

)S/W(n2V

corner

2/12max

V)1n(g

2/12max

2corner

corner )1n(gV

r

2/12/1

2m

2

DSL ])W/T[E(n11

cS/TV

0

VnT

InstantaneousTurn/InstantaneousTurnRatewhereaplanepullsmaxG's(near6rightbeforeblackout)toturnquicklyforashortperiodoftime,turnratevarieswithspeed,usuallybestedatthecornerspeed/cornervelocityofagivenaircraft.Aturnthatquicklyexpelsspeedandpossiblyalt,whileaninstantaneousturnisbydefinitionunsustainable,mosttimestobenomorethana180degreeturnorchangeindirection.Whileusuallybestedatthecornerspeedofthegivenaircraft,thisturncanbeperformedathigherorlowerspeedswithlessbenefit.SustainedTurn/SustainedTurnRatewhereaplanemaximizesitssmallestturnradius,gload,andspeedtoacquirethebestpossibleturnrateandcontinuouslysustainstheturnforlongperiodsoftime,withoutgivingupalt,speed,ordegreesofturn.

Astheabovedefinitionshavedefined,thedifferencebetweenthetwoistheperiodoftimeyou'reabletomaintaintherateofturn.WhileyoucanachieveahighinstantaneousGloadbypullingbackhardonthestick,youwillnotbeabletomaintainthathighrateofturnforverylongbecausethathighGloadwillincreasedragandslowtheaircraft,inreturnthiswillreducethemaximumGobtainable.Conversely,alowerGloadproduceslessdrag.Eventuallyyou'llreachapointwherethrustwillbesufficienttoovercomethedragbeingproduced.ThiswillallowyoutomaintainthecurrentGloadandspeed.Thisiscalledsustainedturnrate.

InstantaneousTurnAnaircraftdesignedforairtoairdogfightingmustbecapableofhighturnrate.

dtd

Whenairtoairmissilesare inuse,thefirstaircrafttoturntowrdstheother aircraft enough to launch amisslewillprobablywin.Inagunsonlydogfight,theaircraftwith the higher turn rate will beabletomaneuverbehindtheother.

Aturnratesuperiorityof20/sisconsideredsignificant.

Sustained turn rate is turn rate atwhich the thrust of the aircraft is just sufficient tomaintainvelocityandaltitudeintheturn.

0DTInstantaneousturnrateisthehighestturnratepossible.Iftheaircraftturnsataquickerrate,thadragbecomesgreaterthantheavailablethrust,sotheaircraftbeginstoslowdownorlosealtitude.

DT LoadFactororgloadingduringaturnistheaccelarationduetoliftexpressedasamultipleofthestandardaccelerationduetogravity.

][gWLn

SWqcn L/

VgWL sin

WL cos Vng

Vg 2/12 )1(tan

cosWL cos

1WLn

1

n12 n 1tan 2 n

Instantaneousturnrateislimitedonlybythrusablemaximumlift,uptothespeedatwhichthemaximumliftexceedstheloadcarryingcapabilityofthewindstructure.Afighteraircraft:nmaxis7.33g,fornewerfightersnmaxis89g

Thespeedatwhich themaximum liftavailableexactlyequals theallowable load factor iscalled hte corner speed and provides the maximum turn rate for that aircraft at thataltitude. Inadogflight,pilots try toget tocorner speedasquicklyaspossible itprovidesbestturnrate.Amodernfighteraircraft:cornerspeedis300350knots[550650km/h]

nqc

SW Lmax

allowablenVn

12

Designspecifications:

Therequired(W/S)canbesolvedas:

?atcombatconditionsnotforlanding

Machnumbereffectwhichreducesmaximumliftathigherspeeds.Buffetingorcontrollabilityconsiderations.

Afighteraircraftwithonlyasimpletrailingedgeflapforcombat: 8.06.0max

LcAfighteraircraftwithcomplexsystemofleadingandtrailingedgeflapswhichcanbedeployedduringcombat:

5.10.1max

LcTheresultingwingloadingmustbedividedbytheratioofcombatweighttotakeoffweighttoobtaintherequiredtakeoffwing loading.Usuallythecombatweight isspecifiedastheaircraftdesigntakeoffweightwithanyexternalfueltanksdroppedand50%ofthe internalfuelgone.Thisisapproximately0.85xWtakeoffformostfighters.Theresultingwingloadingisthemaximumwhichwillallowtherequiredinstantaneousturn.

SustainedTurnThe sustained turn rate isalso important for success in combat. It twoaircraftpasseachotherinoppositedirections,itwilltakethemabout10secondstocomplete1800turnbacktowardstheother.Theaircraftwillprobablynotbeabletomaintainspeedwhileturningatthe maximum instantaneous rate. If one of the aircraft slow down below corner speedduringthistimeitwillbeataturnratedisadvantagetotheother,whichcouldprovefatal.Sustainedturnrateisusuallyexpressedintermsofthemaximumloadfactoratsomeflightconditionthattheaircraftcansustainwithoutslowingorlosingaltitude.Forexample:Theabilityforsustaining4or5gat0.9Mat30000ft[9144m]Ifthespeedistobemaintained: 0DT

DL

WT

WLn

Loadfactorinasustainedturnismaximizedby:

DL

WT ,

2/1

0

kc

c DL mE

0DAec

nq

SW

qSnW

qSLcL Aek

1 withregardlessofthrustavailable.

AeqSWnqSc

AecqSqScT DLD

222

00

Aeqn

SW

SWqSc

WT D

2

/0

Aeqn

AecnWTWTSW D

/2/4//

2

220

Aec

nWT D

02

Thewingloadingtoexactlyattainarequiredsustainedloadfactorusingalloftheavailablethrustcanbedetermined: qScDT D

(T/W)atcombatconditions

offtakecombat

cruise

offtake

offtake TT

WW

WT

0/4/0

22 AecnWT D nosolution availablesolution

,...)(efSW )( Lcfe Athighangleofattacktheeffectiveevaluemaybe

reducedby30%ormore.Becareful!!!

ClimbandGlide

ThesespecifyrateofclimbEngineoutLandinggearpositionFlapsettings sinV

dtdh

ClimbgradientXhG

WDTGsinWDT

cosWL G

WT

WD

AeqS

WSW

qcW

AecqSqScWD DLD

1

//

00

2

Aeq

AecGWTGWTSW D

/2/4)/()/(

0

2 Aec

GWT D

02

availablesolution

hX

TherearenumerousclimbrequirementsforFARormilitaryaircraft.

MaximumCeiling

LqcSW

0DAecq

SW

canbeusedtocalculatethewingloadingtoattainsomemaximumceiling,giventheT/Watthose conditions.The climbgradientG canbe set to zero to represent level flightat thedesiredaltitude.

Aeq

AecGWTGWTSW D

/2/4)/()/(

0

2

forminimumpower

Thismaysuggestawing loadingso lowas tobe impractical,andsoshouldbecomparedwiththewingloadingrequiredtoflyatagivenliftcoefficient:

Forefficiencyduringhighaltitudecruise,the liftcoefficientshouldbeneartheairfoildesignliftcoefficient.

Typicalairfoil:cLis0.5Highaltitudeaircraft,newhighliftairfoils:cLis0.951.0

SelectionofThrusttoWeightandWingLoading

FromtheW/Sestimatedabove,thelowestvalueshouldbeselectedtoensurethatthewingislargeenoughforallflightconditions.Dontforgettoconvertallwingloadingstotakeoffconditionspriortocomparisons.AlowW/Swillalwaysincreaseaircraftweightandcost.IfaverylowW/Sisdrivenbyonlyoneoftherequirements,achangeindesignassumptions(suchasabetterhighliftsystem)mayallowahigherW/S.When thebest compromise forW/Shasbeen selected, theT/W shouldbe rechecked toensurethatallrequirementsarestillmet.Theequations in the lastsectionwhichuseT/Wshouldbe recalculatedwith theselectedW/SandT/W.

InInternationalSystem F15K F15C Mig29K Mig29B JF17 J10 F35A F35B F35C F22

Engine(s)ThrustMaximum(kgf) 26,456(2) 21,274(2) 18,000(2) 16,600(2) 08,300(1) 12,500(1) 18,098(1) 18,098(1) 18098(1) 31,764(2)

AircraftWeightEmpty(kg) 17,010 14,379 12,723 10,900 06,586 09,250 13,290 14,515 15,785 19,673

AircraftWeightFullfuel(kg) 23,143 20,671 17,963 14,405 08,886 13,044 21,672 20,867 24,403 27,836

AircraftWeightMaxTakeoffload(kg) 36,741 30,845 22,400 18,500 12,700 19,277 31,752 27,216 31,752 37,869

Totalfuelweight(kg) 06,133 06,292 05,240 03,505 02,300 03,794 08,382 06,352 08,618 08,163

T/Wratio(Thrust/ACweightfullfuel) 1.14 1.03 1.00 1.15 0.93 0.96 0.84 0.87 0.74 1.14

AircraftType

TakeOffWeightlbs

WingLoadinglbs/ftsq

ThrusttoWeightMilitary

ThrusttoWeightAfterburner

FirstFlightYear

CF105 68,602 56 0.56 0.76 1958

CF18A 35,800 90 0.60 0.89 1978

F16C 26,536 88 0.57 0.94 1974

MirageF1 25,530 94 0.44 0.63 1966

MiG23 38,000 117 0.46 0.67 1967

MiG29 35,000 88 0.64 1.05 1977