課件-1教案第3章

Ch ForcesinTheforcesactingonanweight重力，lift升力，drag阻力 thrust推WeightGravityisthedownwardforceattractingallbodiestowardsthecentreoftheearth.Thegravitationalforceisweight.Thetotalweightoftheloadedaeroplanemaybeconsideredasasingleforceactingthroughthecentreofgravity.thecentreofgravity重心=theweightsupportedperunitareaof=weightofaircraft/wingAtypicaltrainingaeroplane：W=1220kg,S=20m2wingloading=W／S=1220/20=61kg/m2B-747wingloading=500kg/LiftTheproductionoftheliftforcebyanaerofoilisexplainedbyBernoulli’sprinciple.Boundarylayer（邊界層，附面層 flow分離流，separationpoint分離點(diǎn) transition transitionregionAllfluidshaveacertainstickinessandthereforea flow.Thisiscalledviscosity.Gasesarenothighlyviscousbutthereisstilladegreeofstickiness.Inthecaseofawing,themoleculesofairimmediayadjacenttothesurface eattachedtothesurfaceandhavearelativevelocityofzero.Moleculesslightlyfurtherawayfromthewingaredraggedalongbythe‘a(chǎn)ttached’moleculesbeneath.Thefurtherfromthewing,thelesstheairdraggedalong,andhencethegreateristherelativevelocity.Alayerisformed.Thelayersofairthatextendfromthesurfaceouttothefreestreammakeuptheboundarylayer.Thechangefromlaminartoturbulentflowtakesplaceatthetransitionpoint，inthetransitionregionstreamlineturbulentPressure pressuredistributionchangeswith angleofattack.α=40, -40, noliftforce beyondthestallingangle α=αcrit（臨界迎角）LiftfromatypicalThetotaleffectofthispressurepatternistoprovideanetupwardsforce（lift）atpositiveangleofattacktogetherwithanetrearwardsforce（drag）.Thisactingpointisthecenterofpressure（cp）.Liftisacomponentofthetotalaerodynamicforceactingthroughthecp，liftactsperpendiculartotheflightpath.liftfromatypicalLift=L= （q=1/2ρv2）Liftdependswingshape（aerofoilsection）angleofattackairdensity（ρ）airspeed（V2）wingsurfacelift,（CL，“l(fā)iftingForsteadystraightandlevelflight,lift=weightlift lift=weight=L=W=1, a,chordline（MAC:meanaerodynamicchord）b，leadingedge前緣c,trailingedge e,meancamberlinef， g，locationof camber最大彎度位 i，locationof thickness最大厚度位j，leadingedge Airfoil a，typicalwellcamberedaerofoil (high-lift,low-speedwing)；b，typicalhighspeedaerofoil；c，typicallaminar-flowthelaminar-flowlittercamber,fairlysharpleadingedgeradius→agreaterdistancelaminarflow→lessprofiledrag（atlowangleofattack）→highercruisespeed（高巡航速度，lowerfuelconsumption（低油耗，greaterrange（大航程，but→lesslift（athighangleof→airflowseparationismore→lowervalueofCLMAX→higherstallingAlaminarflowwingismoresusceptible（敏感）toasurfacesupercriticalwingsection超臨界剖面（超臨界翼型supercriticalwingsection：flattenthetopreflexcamber（反彎度）toincreaseMCR（criticalMachnumber）→delaytheformationofshockwave（duetotheflattentopsurface）reflexcamberattherearundersurface→increasedcruisingspeed→thegreater2，F(xiàn)actorsaffectingthecoefficientof1BoundarylayerAturbulentboundarylayerproducesmoredragandlessliftbutactuallyremainsattachedtothewingathigherangleofattack,separationisdelayed.2）Angleofattack（AOA）Atlowerangleofattack,thereisalinearincreaseinCLforagivenincreaseinangle,butjustbeforethestallingangleisreached，therateofincreaseofCLreduces.Atthestall,thereisrapidreductionofCLbutnotethatthewingisstillproducingsomelift.Aerofoilshapeandwingplanforma,leading-edge Leading-edgeradiusaffectstheCLatornearthepointofthestallwiththesmallradiusproducingamoresuddenandmoresevereeffectontheCLcurveandthelargeradiusgivingahighervalueofCLandamoreprogressivestallandgentlerflatteningoftheCLbcamberasymmetricalaerofoil：α=0o acambered ForthesameangleofattackthesymmetricalsectionhasalowervalueofCL，butthecamberedsectiongivesahighervalueofCLandalsoproducesahigherumvalueofCLatthestallandalowercriticalangleofattack.c,aspectratioTheliftofalowaspectratiowingwillincreaseatalowerratewithincreasingangleofattackthantheliftonahighaspectratiowing.dsweepbacke,surface Roughnessofthewingsurfacewilleffecttheconditionoftheboundarylayerandthusabilityofthewingtogeneratelift.Reynolds Re, L=chordlength 弦長 IfVisincreased,ReynoldsNumberwillincreaseandsotheairflowhasmoreenergy,givingahighervalueofCLmax.Thisisbecauseathigherspeeds,forsameangleof attack,theboundarylayerwillreceivemorekineticenergywhichwillresultindelayedseparationandconsequentlyahigherumvalueofCL.AreductionofindensityathighaltitudewillreduceReandreduceCLmax.Againthereasonislinkedwiththeenergyoftheboundarylayer.AlowerdensitygiveslowermassandhencekineticenergysincekineticenergyisafunctionofmassaswellasMachnumber數(shù) v：true a：localspeedofsoundThecoefficientofliftwillincreasewithincreasingMachnumberatlowairspeed.3，Thecentreof α↑→CL↑（increasingtheliftingabilityofwing）→CP CPmoves※donotconfusethepitchattitudeofaircraft（thelongitudinalaxishorizonwithattac（therelativetotheairflow）andwiththeangleofincidence（thelongitudinalaxisrelativetothechordline）.theangleof longitudinal Highlifthighliftdevices力裝置，增升裝1，Usinghigh-liftdevicesforexample：cruise Vcru=120stallingspeed Vs=60knots,CL↑fourtimesthecoefficientoflift.Usinghigh-liftdevices,togivetherequiredadditionalliftatalowerspeed.Instraightandlevel L=W=H=const.→ρ=const.,s↑andchangingaerofoilshapeTherequiredliftcanbegeneratedatmuchlowerspeeds.Thisisthepurposeofthehigh-liftdevices.L=W= Vs=√2W/（ρsCLmax）CLmax↑2，thetypesofhigh-liftleadingedgedevicesslats縫翼：increasingtheliftcoefficientatveryhighangleofattack.Slatscausesomeofthehighenergyairflowbeneaththewingtoflowthroughaslotandovertheuppersurfaceofthewing,therebydelayingseparationandthestall,allowingtheaeroplanetoflyatahigherangleofattackandalowerairspeed.leadingedgeflaps前緣襟翼：changingtheeffectiveoftheleadingedge，controllingtheflowathigherangleofKrugerflaps襟翼：improvingleadingedgeflowcondition，delayingleadingedgeseparation.Functionofleadingedgedevicesis①usingthegapflow（slat-fixedslotsandautomatic②droothefrontsectionofwing（leadingedgeusingKrugerflapswhichfoldout（折疊）fromundertheleadingedge 2-wingtip3-aileron4-trailingedgedevicessimpleflaps（plainflaps）split slotted 開縫襟翼（asingleslotormultipleslotsFowler Thetrailingedgeflapsincreasethecamberoftheaerofoilsection,orwingareaorusinggapflow.Thegreaterthemeancamberline,thegreaterthelift（theumCLpossible）ofthewing.3,effectsofflapsincreased “aballoonpitchingCPmovesaft→longermomentarm→nose-downdecreasedlift/dragThedragincreaseisgreaterthantheliftincreases，soincreased “l(fā)iftflaps “drag5）lowerstallingflapsdown→lowerstallingangle→flatter4,flapsfortake-attake-offpositionbypartiallyloweringthe→CL↑，CD↑（asmallpenalty）→lowerspeed→ashortertake-offgroundrunWhenretractthe→CL↓→aircraftsinks（needtorisethenose,→reductionofthecamberattherearofthe→movingthecentreofpressureforwards→thenosetopitch→retrimming5,flapsforapproachandatapproachandlandingbyloweringtheflaps→CL↑，CD↑↑→alowerspeedballooning-pitchattitude-movingthecentreofflapsincreasethepilotforwardview（視野Withtrailingedgeflapsextended,theaeroplane’srequirednoseattitudeislower→Theimprovesforwardviewforthepilot.DragDragactsintheoppositedirectiontotheaircraft’smotionthroughtheair.Thethrustisto edrag.Thelowerthedrag,thelessthethrustThrustaboveandbeyondthatrequiredto edragisusedtoclimb,accelerateandmanoeuvretheaircraft.ItiscalledexcessTotaldragisthesumofallforcesactingparalleltoflight-pathoftheaircraft.Atsubsonicspeedsitisnormaltosubdividedragintotwomain▲parasite （alsoknownaszero-liftdrag零升阻力▲induced （sometimesreferredtoaslift-dependentdrag升致阻力Cd=Cd0+ParasiteParasitedragincludessurfacefrictiondrag，formdragandinterferencedrag.1，surfacefrictiondragSurface（orskin）frictiondragislargelydeterminedbythetotalareaoftheaircraftthatisexposedtotheairflowingpastit.（wettedarea浸潤面積）Thetypeofboundarylayerpresentalsohassignificanteffectwithlaminarflowcreatinglesssurfacefrictiondragthantheturbulentflow.Thethirdfactoraffectingsurfacefrictiondragisthecoefficientofviscosityoftheair.Thegreatertheviscosity,thegreaterthedraggingeffectoftheair.pressuregradientadversepressuregradient逆壓梯度，反壓梯度reversepressuregradient逆壓梯度，反壓梯度favorablepressuregradient順壓梯度Forminimumsurfacefrictiondrag,thetransitionfromlaminartoturbulentmustbedelayedaslongaspossible.2，form Whentheboundarylayerfinallyseparates,theseparatedflowstillimpactsagainstsurfacecausingdrag.Thisisformdrag.Effectsaremadetodelayseparationoftheboundarylayerinanattempttoreduceformdrag.Withgreaterkineticenergy,theboundarylayercanresisttheeffectsoftheadversepressuregradientforlonger,thedelayingseparationandreducedrag. 尾跡，protuberance突起物，finenessfairing整流罩，iceaccretionfrontalarea迎風(fēng)面積（最大橫截面積3，interferencedragThetotalparasitedragofanaeroplaneisgreaterthanthesumofsurfacefrictiondragandformdrag.Theadditionaldragiscausedbymixing,orinterferenceoftheboundarylayerairflowatthejunctionofvarioussurface，suchasatthewing/fuselagejunction，thetailsection/fuselagejunctionandthewing/enginenacellejunction.Suitablefilleting（fairingstreamliningofshapesminimizethisinterferencedrag.4，summaryofparasiteParasitedragincreaseswithairspeed,atveryhighspeedsnearlyallthetotaldragiscausedbyit.Thepredominanceofparasitedragathighspeedsshowstheneedforaerodynamic“cleanness”toobtainumperformance.ParasitedragisdirectlyproportionaltothesquareofTAS,doublingthespeedwillquadrupletheamountofparasiteInduced1，Howinduceddragisvortexvorticesvortexes（復(fù)數(shù)）旋渦wingtipvortex翼尖渦 induceddownwash downwashangle下洗角remoteflow InduceddragisadirectresultoftheaircraftproducingThedifferenceinpressurebetweentheupperandlowersurfaceofthewingcausesairtospillaroundthetip,deflectingtheuppersurfaceflowtowardsthefuselageandthelowersurfaceflowtowardthetips.Asthetwoflowsmeetatthetrailingedgeaseriesofvorticesisformed,whichaccumulateatthetiptoformalargewingtipvortex.Whenthepressuredifferencebetweentheupperandlowersurfaceincrease（morelift,Productionoflift→wingtipvorticesandtrailingedgevorticesform→downwash→localrelativeairflowdirectionchanges→liftisinclinedbackward→induceddrag（paralleltotherelative2，F(xiàn)actorsaffectinginduceddrag ellipticalplanform：Cdi=CL2/πA A=aspectratioTheellipticalplanformhasminimuminduceddrag.2）aspect b=spanlength s=wingarea c=meanchordAtthesameareaofwing,anarrowwingofhighaspectsmallwingtips）hasweakerwingtipvortices,lessinduceddownwashandlessinduceddrag.effectofliftandL=1/2ρv2sCLatagivenspeedL↑→CL↑effectofInlevelflightV↓→CL↑→α↑→Cdi↑V↑→CL↓→α↓Theslowerweflythegreatertheangleofattackhencethegreaterthedownwashangle.Thisincreasesthevalueofinduceddrag.Thisistheoppositetoparasitedrag,wherethefasterweflow,thegreaterthedrag.1Summaryofcausesandeffectsofinduceddraga,Wingtipvorticesform.b,Thewingtipvorticescausethec,Thedownwashdeflectstheoriginalremoteairflowdown→downwashangled,Theeffectiveliftvectoristiltede,Therearwardcomponentofthetiltedliftvectoristheinducedf,Thehighertheangleofattack,thegreaterthedownwashangle,andthegreatertheinduceddrag.3，Reducinginduced wingtip Wingtipandmodifiedwingtipcanreducetheleakage（泄漏ofairflowaroundthewingtipandthereforereducetheinducedAlso,theinstallationofwingfencesreducesspanwiseflowandthusinduceddrag.washoutwashout-Thewinghasaninbuilttwistwhichreducestheangleofincidencefromthewingroottotip.Washout→lessseverewingtip→lessinduced→lessbendingloadonthewing→moredocile（馴順）behavioratthetapered Ataperedwinghasweakerwingtipvorticesandsotheinduceddragisless.highaspectratio4,FlightconditionsthatincreaseinducedlowairspeedandhighangleofInstraightandlevel L=W=1/2ρv2sCLV↓→CL↑→α↑→toformgreaterwingtipvortices,greaterdownwashbehindthetrailingedgeofthewing→theliftforcetiltedfurtherback→induceddrag↑approachingthestallingnearthestallingspeedinlevelflightinduceddrag/total％,atcruisespeedinlevelflightinduceddrag/totaldrag≈10％3）increasedliftproductionatsame weightW↑→manoeuvringL↑（whenturn盤旋Underconditionsofhighlift,pressuredifferentialbetweentheloweranduppersurfaceincreases,resultinginstrongerwingtipvortices→increasedinduceddraggroundeffectIfthewingisclosetothesurfaceoftheseaorflatground,thedownwashbehindthewing,especiallythewingtipvorticesaredeflected.Thevectorofthetotalreactionislesstitled→itdecreasestheinducedraglift 海Ifthewingisraisedprematurely（過早地）theaircraftclimbsbrieflyandistakenoutofgroundeffect→reducedliftandincreaseddrag.Itcansettlebackdown,especiallyiftheflapshavealsoretractedprematurely→raisingthenosefurthertoincreaseincreasesinduceda,liftoffatthe mendedspeedb,donotretracttheflapsprematurelyc,onhotdaysathighelevation,liftoffatahigherthannormalspeedanddonotrotatetotheliftoffattitudeuntilthisspeedisachieved.Ifthespeedisslightlyhigh,theaircraftwillentergroundeffect,feeltheincreasedliftandreducedinduceddragandwillcontinuetofloatforalongdistance→runway（跑道）Totaldrag=parasitedrag+induceddragparasitedrag∽（IAS）2induceddrag∽minimumdragpoint-minimumdragspeedVIMD-Attheminimumdragpointthetotaldragisaminimum,andtheparasitedragandtheinduceddragareequal.thestall→asharpriseinthetotaldragduetotherapidincreaseininduceddrag1,EffectofInlevelflight W↑→CL↑→Cdi↑→induceddragDi↑→minimumdragVIMD 2 landinggear configurationchanges（extensionoflandinggearandspeedbrake）→parasitedragD0↑→totaldragD↑→minimumdragspeedVIMD↓（extraservicedeployedconfiguration額外設(shè)施打開的構(gòu)型3,Effectofaerofoiltoretainalaminarboundarylayeraslongaspossible→reducesurfacefrictiondrag.4，Effectofif/dgao升阻比L ∽， D ∽αLft=（2（vsdrg（2（vsC）lift/drag=（1/2）×（ρv2sCL）/（1/2）×（ρv2s=CL/Theefficiencyofanaircraftislift/drag（L/DorBothliftanddragarecomponentsofthesametotalaerodynamicforce,theefficiencyofanaircraftdependsontheangleofthetotalaerodynamicreactiontothefreestreamflow.Atthestallingangleisapproached,thedragincreasesatagreaterratebeyondthestallangletheCLdecreases.Atthestall,thebreakdownofstreamlineflowandtheofturbulence,orvortices,causesalargeincreaseinTheangleofattackforumlift/dragissignificantlylowerthanthatforumlift.ThepeakvaluesofCL,CDandCL/CDoccuratonespecificangleofattack.Tosatisfyaparticularrequirement,wecanselecttheoptimumangleofattack.1,VariationoftheL/DratiowithangleofTheangleofattackisthemostefficientangleofattackthatgivesthebestlift/dragratio.bestL/Dratio→theumcruisingrange（forpropeller→theumglidingdistanceInstraightandlevelflightataconstantweightL=W= 2,DecreasedL↓=W↓= V=constant→CL↓→3,ChangingcruiseL=W= rocket火箭jetengine噴氣發(fā)動(dòng)機(jī)，pistonengine活塞式發(fā)動(dòng)機(jī),propeller螺旋槳blade槳葉，葉片torque扭矩gearbox齒輪箱revolutionperminute每分鐘轉(zhuǎn)速（rpm）,shaft軸Thepropellerconvertstherotationoftheengineshaftintoapistonengine：apistonmovesupordown→therotationofthepropellershaft→thebladegeneratestheliftanddrag→thrust1Planeof Theplaneofrotationisperpendiculartothepropeller2Blade Thebladeangleistheanglebetweenthechordlineofthepropellerbladeandtheplaneofrotation.fixed-pitch 定距螺旋槳（Thebladeangleisfixedvariable-pitchpropeller變距螺旋槳（ThebladeangleisvariableThebladeangleisnotconstantoverthelengthofthepropeller3Propeller 進(jìn)距fine coarsepitch Bladeangleandpitcharemeasuredatstandardradius.standardradius：thesectionat75％ofthepropellerdiscAdvanceisthedistanceforwardthatbladetipwouldtravelincomplete4BladetwistThepropellerbladeistwistedalongitslengthsothatthebladeangleisgreatestattherootandsmallestatthetip.Becausethebladeistwisted,itisnormaltostatethebladeangleat75％ofthebladelengthfromthehub（槳轂）.linearvelocitydistributionalongthepropellerfromroottoThelinearvelocityofthepropellerincreasestowardthetip,becausethedistancetraveledinthesametimebythetipcomparedtothehubismuchhelixangle螺旋角：theanglebetweenbladepathandtheplaneofrotation,whentherpmisconstantforthewholepropeller,butthelinearvelocitygeneratedbytherotationchanges.Becauseeachsectionofthebladehasadifferentlinearrotationalvelocity,theangleofattackofthatsectionisdifferentfromanyothersection.Itisimportanttoappreciate（理解）therelationshipofspeedtoforwardspeedandtheeffectontheangleofattackofthebladesection.5Helical Thepathaparticularsectionfollows（遵循）iscalleditshelical6,PropellervelocityandAsthepropellerrotates,ithasarotationalvelocityandasaircraftmovesforward,thepropellerhasaforwardTheangularvelocityofallpointsalongthepropellerbladeisthesame,butthelinearspeedisincreasedfromthehubtowardthetip.Thishastheeffectofadifferentrelativeairflowdirectionatallpointsalongtheblade.Thepropellerpathisdifferentforeachpointalongthebladebecauseofthedifferentlinearvelocity.7,PropellerangleofTheangleofattackistheanglebetweentherelativeairflowandthechordofthepropeller.Asdirectionofrelativeairflowchangeswithpropellerrpmandaircraftforwardspeed,theangleofattackchanges.8,Forcesactingonthetorque Thepropellerbladeadvancesintotherelativeairflowatanangleofattackwithatotalreactionbeingproduced.thetotal→oneparalleltothedirectionoftheflight→oneparalleltotheplaneofrotationThetorquereactionisoppositetothedirectionofrotationandisbalancebythetorqueoftheengine.twisting Therearetwo→oneduetocentrifugalforces（離心力→oneduetoaerodynamicforces（空氣動(dòng)力）a，centrifugaltwistingmoment（CTM）離心扭轉(zhuǎn)力矩Thecentrifugalreactionproducesatorqueforceaboutthepitchchangeaxis（變矩軸）b，aerodynamictwistingmoment（ATM）空氣動(dòng)力扭轉(zhuǎn)力矩Thetotalreactionisnotcoincidentalwiththeaxisofblademechanism.Ifthetotalreactionisaheadofthepitchchangeaxis,theaerodynamictwistingmomentisattemptingtoincreasethebladeIftheCPisbehindtheaxis,willtendtodecreasethebladethrustbendingAthrustbendingforceattemptstobendthepropellerbladesforwardatthetips,becausethelifttowardthetipoftheblade thinbladesection Thrustbending forceopposescentrifugalreaction（duetorotation） 彎曲 9 Apropellerisusuallydrivenbytheengine.Thereareoccasionswhenthepropellermightdrivetheengine,andthisisknownaswindmilling-perhapsasteepdivewithpoweroff,asuddenreductioninpoweroranenginefailure.dive俯沖,poweroff仃車,failure10Propeller geometric 滑geometricpitch–Thepitchofapropellerisanexpressionofthedistancethepropellerwouldmoveforwardinonerevolutionwiththehelixangleequaltothebladeangle（angleofattackiszero）effectivepitch–Theeffectivepitchistheactualdistancepropellermovesforwardduringoneslip–Thedifferencebetweenthegeometricandeffectivepitchiscalledtheslip.Thereferencepointforthebladeangleis75％bladeForfixed-pitchpropeller,bladeangle=const.,aconstantrotationalvelocity（rpm=const.）aconstantforward rpm↑11,PropellerThefurtheroutalongthebladesection,thefasteritsrotationalvelocity.Thehighertherpmofthepropeller,thefastertherotationalvelocity.forwardTheforwardmotionissuperimposed（迭加）ontherotationalmotionofthebladesectiontogiveitanoverallresultantvelocity.12,propellerTherewillbeaerodynamiclossesbothnearthepropellerhubandatthetip，nearthehubduetoairflowinterferenceatthetipduetoformationofvortices.Asmallpartofthewholepropellerblade（about60－90％ofradius）iseffectiveinproducingThegreatestusefulthrustisproducedatapproximay75％ofthetipradius.13,ForcesonabladeThedirectionoftherelativeairflowandthedirectionofflightofanaeroplanearenotparallel.Therelativeairflowchangesitsdirectionalongthepropellerbladedependingonhowfarthatsectionisfromthehub.Thetotalreactionisresolvedintotwopropellertorqueforce,intheplaneofthrust,inthedirectionperpendiculartotheplanof3.5.2Propeller Forafixed-pitchpropeller,iftherpmisconst.,thenthedirectionoftherelativeairflow,andthereforetheangleofattackwillbedeterminedbytheforwardspeed.Atlowspeed,theangleofattackwillclosetothecriticalangleofattack,andatcruisespeedtheangleofattackwillbebestangleofattack.Asspeedisincreased,theangleofattackwillreduceuntilthereiszerooranegativeangleofattack.Foragivenrpm,therewillbeonlyoneairspeedatwhichthepropellerwilloperateatitsmostefficientangleofattack.Thedesignerwouldchooseafixed-pitchpropellerwhosebest-efficientairspeed/rpmcombinationsuitstheaeroplane’sintendedpurpose.Toexpandthefightenvelopeoftheaircrafttherewereseveralphysicallychangethepropellertosuittheadjustthebladeangleontheground；adjustthebladeangleintheflightAtlowairspeedthebladeangleneedstobesmallfortheangleofattacktobeoptimum.Thisisknownasfinepitch.Astheforwardspeedincreases,thebladeangleneedstoincrease,orcoarsen,fortheangleofattacktoremainoptimum.Highrpmisfinepitch.LowrpmiscoarseFinepitch（highrpm）isusedfortake-offandclimb.Coarsepitch（lowrpm）issetforcruise.Theaimistohavethepropellerclosetothebestangleofattackandtheenginerpmsetforumefficiencythroughouttheaircraft’sairspeedrange.3,Advantageofconstant-speedAvariable-pitch（constant-speed）propelleradjuststotheefficientangleofattackoverawiderangeofrpmsandAfixed-pitchpropelleronlyoperatesefficiencyundertheonesetofrpmandairspeedconditions.changeofthrottle油門,leverThepilotselectsthedesiredrpmusingthepropellerWhenthethrottleisadvancedthepropellerbladeangleautomaticallyincreasestoabsorbanyextraenginepowerd,andyetstillretainsthesamerpm.i.e.constant-speed,butwithincreasedthrust.Theincreasedthrustcanbeusedtoaccelerateortoincreaserateofclimbortoreduceratethedescent.changeofAmajorconsiderationsinengineoperationistheavoidanceofan3.5.3EffectofEffectofpropelleristhedynamicandaerodynamiceffectsofAllsingle-engineaircraftshavedirectionalproblemsbecauseoftheinbalanceofforcescausedbytherotationpropeller.1，Slipstream slipstream滑流,cockpit座艙,asymmetricclockwise順時(shí)針anti-clockwisefin鰭,立尾offset補(bǔ)償,wheeltyre輪