《直升机空气动力学与飞行原理》课件-模块九：直升机特殊飞行（双语）

模块九：直升机特殊飞行Learnabouthelicopter

specialflight直升机空气动力学与飞行原理Helicopteraerodynamicsandprinciplesofflight模块九：直升机特殊飞行Learnabouthelicopterspecialflight任务一：理解直升机自转状态Understandhelicopterself-rotatingstatus直升机空气动力学与飞行原理Helicopteraerodynamicsandprinciplesofflight活动1：什么是直升机自转状态？01.PARTONEWhatisahelicopterself-rotatingstatus？活动1：什么是直升机自转状态？自转状态属于无动力飞行，是直升机所特有的空气动力学现象，也是关系飞行安全的重要问题。Self-rotating,belongingtounpoweredflight,isacharacteristicaerodynamicphenomenonofhelicoptersandanimportantissueconcerningflightsafety.活动1：什么是直升机自转状态？当发动机失效或人为停车，在下降过程中必须有其它力来维持旋翼转速保持直升机飞行直至着陆，可以由流过旋翼的气流提供能量，以克服桨叶阻力让旋翼旋转，这个过程就是自转。Whentheenginefailsorisstoppedartificially,otherforcesmustbepresentduringdescenttomaintainrotorspeedtokeepthehelicopterflyinguntillanding,whichcanbepoweredbyairflowthroughtherotortoovercomebladedragtospintherotor,aprocessknownasself-rotating.活动1：什么是直升机旋翼失速？中国传统的民间儿童玩具竹蜻蜓，凝结了中国古代智慧的结晶，能在空中对抗风力而产生自旋，这种现象叫风车状态，其原理与直升机类似。Chinesetraditionalfolkchildren'stoysbamboodragonflies,condensedthecrystallizationofancientChinesewisdom,canbeintheairagainstthewindandproducespin,thisphenomenoniscalledwindmillstate,theprincipleissimilartothehelicopter.活动1：什么是直升机旋翼失速？与竹蜻蜓不同的是，直升机利用旋翼原有的旋转动能和直升机的势能，操纵直升机进入自转状态且垂直下降率达到规定值，这种现象叫旋翼的自转下降。Unlikethebamboodragonfly,thehelicopterutilizestherotor'soriginalrotationalkineticenergyandthehelicopter'spotentialenergytomaneuverthehelicopterintoastateofself-rotationandtheverticalrateofdescentreachesaspecifiedvalue,aphenomenoncalledrotor'sself-rotationdescent.活动1：什么是直升机旋翼失速？自转下降与竹蜻蜓的风车状态类似，但风车状态大多指的是产生扭矩，而自转下降强调的是产生拉力。Thespindownissimilartothewindmillstateofthebamboodragonfly,butwhilethewindmillstatemostlyreferstothegenerationoftorque,thespindownemphasizesthegenerationoftension.活动2：直升机自转状态的应用场景？02.PARTTWOWhatistheapplicationofhelicopterself-rotatingstatus?活动2：直升机自转状态的应用场景？直升机在合适的时机进入自转状态可以有效避免人员财产损失，下列情况直升机应做自转下降：Helicopterscaneffectivelyavoidlossofpersonnelandpropertybygoingintoself-rotatingattherighttime.Helicoptersshoulddoanself-rotatingdescentinthefollowingsituations:活动2：直升机自转状态的应用场景？发动机发生故障，如空中停车或因发动机振动太大而被迫关车，驾驶员应以自转飞行方式来寻找迫降地点。Intheeventofanenginefailure,suchasanin-flightstoporforcedshutdownduetotoomuchenginevibration,thepilotshouldautorotatetofindacrashlandingsite.尾桨由于某种原因失效，不能平衡反扭矩时，为了安全着陆，驾驶员应关闭发动机，进入自转飞行并着陆。ThetailrotorfailedforsomereasonandcouldnotbalancethecountertorqueAtthispoint,inordertolandsafely,thepilotshouldshutdowntheengine,enterself-rotatingandland.活动2：直升机自转状态的应用场景？活动2：直升机自转状态的应用场景？直升机需陡降，为快速下降高度而不致陷入涡环状态。Helicoptersarerequiredtomakeasteepdescentinordertomakearapiddescenttoaltitudewithoutgettingcaughtinavortexring.活动2：直升机自转状态的应用场景？在发动机失效的初始瞬间，飞行员必须立即将总距杆放到最低桨距位置，否则的话，主桨转速将迅速减小而引起桨叶锥体角迅速增大，桨叶快速向上挥舞。Attheinitialmomentofenginefailure,thepilotmustimmediatelyputthetotalpitchlevertothelowestpitchposition;otherwise,themainpropellerspeedwilldecreaserapidlycausingarapidincreaseinthebladeconeangleandarapidupwardswingoftheblade.活动2：直升机自转状态的应用场景？这是因为功率失去后无法克服桨叶的型阻，大桨叶角会使阻力较大，旋翼转速会迅速下降。Thisisbecausethelossofpowercannotovercomethetyperesistanceofthepaddles,andalargepaddleanglewillresultinalargerresistanceandarapiddecreaseinrotorspeed.活动2：直升机自转状态的应用场景？随着旋翼转速的迅速减小，离心力将无法再保持住理想的锥体角，锥体角将迅速增大，造成桨叶根部应力迅速增大而引起桨叶大梁弯曲甚至完全折断。Astherotorspeeddecreasesrapidly,thecentrifugalforcewillnolongerbeabletoholdtheidealconeangle,andtheconeanglewillincreaserapidly,resultinginarapidincreaseinthestressattherootofthepaddleandcausingthepaddlebeamtobendorevenbreakcompletely.活动2：直升机自转状态的应用场景？在完全放低总距杆的同时，飞行员还必须松开脚蹬，使尾桨距减小，同时操纵周期变距杆，保持约60kn的前飞速度。Whilefullyloweringthepitchstick,thepilotmustalsoreleasethefootpegstoreducethetailrotorpitch,andatthesametimemaneuverthecyclicpitchsticktomaintainaforwardspeedofapproximately60kn.活动2：直升机自转状态的应用场景？完成上述动作后，直升机将进入下降飞行通道且保持一定的前飞速度。Aftercompletingtheabovemaneuvers,thehelicopterwillenteradescendingflightpathandmaintainacertainforwardspeed.活动3：直升机自转下降时如何操纵？03.PARTTHREEHowtomaneuverahelicopterinaself-rotatingdescent？活动3：直升机自转下降时如何操纵？自转下降分为三种形式:自转下降到复飞自转下降到着陆巡航中自转下降Self-rotatingdescentisdividedintothreeforms:self-rotatingdescenttogoaroundself-rotatingdescenttolandingself-rotatingdescentincruiseNO1.Entry:Lowercollectivepitchstick,throttleofftoidlewhileyawcorrection,heightcorrectionwithstick;活动3：直升机自转下降时如何操纵？01.进入:下放总距杆，关油门到慢车，同时修正偏航，带杆修正高度;高空中自转下降的操纵特点总结Thehandingcharacteristicsofself-rotatingdescentathighaltitudearesummarizedas:活动3：直升机自转下降时如何操纵？02.自转下降中:检查旋翼转速、空速，保持协调飞行;高空中自转下降的操纵特点总结03.复飞:打开油门，上提总距杆，设定上升功率，直到到达上升高度。NO2.Inself-rotatingdescent:checkrotorrpm,airspeedandmaintaincoordinatedflight;NO3.Goaround:Openthethrottle,raisethecollectivepitchlever,andsettheascentpoweruntiltheascentaltitudeisreached.活动3：直升机自转下降时如何操纵？若直接着陆不进行复飞，则在到达复飞高度时，继续下降高度，在高度至6-3英尺时，根据下降快慢协调一致地上提总距杆，并向前顶杆，使滑撬与道面平行，用舵保持方向。接地后，把总距杆柔和地放到底。Ifadirectlandingdoesnotperformagoaround,continuethedescentatagoaroundaltitudeof,atanaltitudeof6–3feet,pullupthecollectivepitchstickinunisonwiththerateofdescent,andpushthestickforwardsothattheskidsareparalleltothepavement,withruddertomaintaindirection.Aftertouchdown,gentlylowerthecollectivepitchbartothebottom.活动3：直升机自转下降时如何操纵？巡航中自转下降，可以根据选择的着陆点进行航程自转下降Self-rotatingdescentincruise,withtheabilitytomakeavoyageself-rotatingdescentbasedontheselectedlandingsiteSummary总结任务二：理解直升机自转状态Understandhelicopterself-rotatingstatus01什么是直升机自转状态？Whatisahelicopterself-rotatingstatus?02直升机自转状态的应用场景？Whatistheapplicationofhelicopterself-rotatingstatus?03直升机自转下降时如何操纵？Howtomaneuverahelicopterinaself-rotatingdescent？Thinking思考回忆童年，体验竹蜻蜓的飞行姿态，对比直升机自转下降和风车状态的区别？模块九：直升机特殊飞行Learnabouthelicopterspecialflight任务二：理解直升机涡环状态Understandhelicoptervortexringstatus直升机空气动力学与飞行原理Helicopteraerodynamicsandprinciplesofflight活动1：什么是直升机涡环状态？01.PARTONEWhatisahelicoptervortexringstatus？活动1：什么是直升机涡环状态？直升机作垂直下降或以小空速飞行时，如果下降率较大，向上气流会阻碍滑流运动，其中一部分空气重新吸入旋翼中的现象，称为涡环状态。Whenahelicopterisdescendingverticallyorflyingatlowairspeeds,iftherateofdescentishigh,theupwardflowobstructstheslipstreammotion,withsomeoftheairreingestingintotherotor,aphenomenoncalledvortexringcondition.活动1：什么是直升机涡环状态？直升机处在涡环状态中飞行，此时发动机仍然处在工作中，即使飞行员采用发动机全功率，直升机仍然保持下沉，所以也可以采用“大功率下沉”这个术语来描述这种特殊飞行状态。Thehelicopterisflyinginthevortexringstate,whentheengineisstillinoperation,evenifthepilotusesthefullpoweroftheengine,thehelicopterisstillsinking,sotheterm"highpowersinking"canalsobeusedtodescribethisspecialflightstate.活动1：什么是直升机涡环状态？直升机下降中，旋翼上面吸入的空气与自下而上的相对气流流相遇，在压力差作用下，有少部分空气从旋翼下面自下而上地向旋翼上面低压区流动。经过多次循环，就形成了桨尖涡流。Whenthehelicopterisdescending,theairinhaledabovetherotormeetstherelativeairflowflowfromthebottomup,andasmallportionoftheairflowsfrombelowtherotortothelow-pressureareaabovetherotorfromthebottomupunderthepressuredifference.Aftermanycycles,thetipvortexisformed.活动1：什么是直升机涡环状态？桨尖涡流是形成涡环状态的内因，而直升机的垂直下降则是形成涡环状态的外因。Thepaddletipvorticesaretheinternalcauseoftheformationofthevortexringstate,whiletheverticaldescentofthehelicopteristheexternalcauseoftheformationofthevortexringstatus.活动1：什么是直升机涡环状态？尾桨也会形成涡环状态，两者形成的原因相似。直升机尾桨涡环形成与偏转角速度有关，直升机向某一方向悬停转弯角速度过快时，尾桨也可能陷入涡环状态。Thetailrotorcanalsoformavortexring,andthereasonsfortheirformationaresimilar.Helicoptertailrotorvortexringformationanddeflectionangularvelocity,helicopterhoveringinacertaindirectionturningangularvelocityistoofast,thetailrotormayalsofallintothevortexringstate.活动1：什么是直升机涡环状态？涡环状态出现后，将会造成气流分离、低频振动、产生额外噪音以及升力减小等现象，旋翼产生的拉力减小，下降率增大。下降率越大，涡环现象越严重，旋翼拉力减小越多。Afterthevortexringstateoccurs,itwillcauseflowseparation,low-frequencyvibration,additionalnoisegeneration,andreducedlift,reducingthepullgeneratedbytherotorandincreasingtherateofdescent.Thegreatertherateofdescent,themoreseverethevortexringphenomenonandthemorereducedtherotorpull.旋翼拉力忽大忽小，引起旋翼和直升机发生抖动，摇晃现象，操纵性变差，严重时可能造成操纵失效。Rotorpullvaries,causingtherotorandhelicoptertoshake,shake,andpoorhandling,whichcancausecontrolfailureinseverecases.活动1：什么是直升机涡环状态？活动1：什么是直升机涡环状态？涡环状态造成的振动极易使得旋翼产生疲劳强度破坏，如裂纹、断裂等，因此在进行维护工作时，要保持良好的维护作风和工作规范，对工作认真负责。Thevibrationcausedbythevortexringstateisveryeasytomaketherotorproducefatigue

strengthdamage,suchascracks,fractures,etc.Therefore,whencarryingoutmaintenancework,weshouldmaintainagoodmaintenancestyleandworknorms,andbeconscientiousandresponsibleforthework.活动2：涡环状态的形成场景02.PARTTWOScenesoftheformationofvortexringstatus活动2：涡环状态的形成场景当直升机发动机正常工作，且直升机处于悬停状态（Vy=0），不会形成涡环，只形成少量桨尖涡流(如图A所示）。Whenthehelicopterengineisworkingproperlyandthehelicopterisinhover(Vy=0),novortexringsform,onlyasmallnumberoftipvorticesform(asshowninfigureA).活动2：涡环状态的形成场景当直升机发动机正常工作，且直升机处于垂直下降状态，形成少量涡环(如图B所示）。Whenthehelicopterengineisworkingproperlyandthehelicopterisinaverticaldescent,asmallnumberofvortexform(asshowninfigureB).活动2：涡环状态的形成场景当直升机发动机正常工作，且直升机垂直下降速度较快，会形成强烈的涡环(如图C所示）。Whenthehelicopterengineisworkingproperlyandthehelicopterisdescendingverticallyfaster,strongvortexringsform(asshowninfigureC).活动2：涡环状态的形成场景当直升机发动机正常工作，且直升机垂直下降速度更快，向上的气流会吹掉涡环(如图D所示），进入旋翼自转。Whenthehelicopterengineisworkingproperlyandthehelicopterisdescendingverticallyfaster,theuowardsirflowblowsawaythevortexring(asshowninfigureD)intorotorrotation.活动3：如何预防或改出涡环状态？03.PARTTHREEHowtopreventorchangeoutofvortexringstatus?活动3：如何预防或改出涡环状态？01.如无特殊需要，特别是高度在10～200m时，不要做垂直下降，宜做带空速的下降。（一）要防止进入涡环状态，飞行中应注意如下几点Toprevententeringthevortexringstate,thefollowingpointsshouldbenotedduringflight:(1)Ifthereisnospecialneed,especiallywhentheheightis10~200m,donotdoverticaldescent,itisadvisabletododescentwithairspeed.活动3：如何预防或改出涡环状态？02.做垂直下降或小速度下降时，下降率不要太大。（一）要防止进入涡环状态，飞行中应注意如下几点03.在剩余功率较小的情况下(如载重大、海拔高度高或气温高等)，不要勉强做悬停或垂直上升。(2)Whendoingverticaldescentorsmallspeeddescent,thedescentrateshouldnotbetoobig.(3)Inthecaseofsmallresidualpower(suchaslargeload,highaltitudeorhightemperature),don'tbereluctanttodohoveringorverticalrise.活动3：如何预防或改出涡环状态？改出涡环状态的一般作法就是操纵总距杆。如果发现直升机垂直下降率增大，是由于发动机功率不足引起的，则应及时地上提总距杆，迅速增大发动机功率，以制止下降率继续增大。Ifitisfoundthatthehelicopterverticalrateofdescentincreasesduetoinsufficientenginepower,thecollectivepitchbarshouldberaisedintimetorapidlyincreaseenginepowertostoptherateofdescentfromcontinuingtoincrease.活动3：如何预防或改出涡环状态？如果上提总距杆也不能制止下降率继续增大，在一定的高度以上则应迅速地前推驾驶杆，使直升机产生前飞速度，把涡环吹掉，脱离涡环状态。Ifraisingthecollectivepitchbardoesnotstopthedescentratefromcontinuingtoincrease,pushthestickforwardquicklyaboveacertainaltitudetoallowthehelicoptertodevelopforwardflightspeed,blowingthevortexringoffandoutofthevortexringcondition.活动3：如何预防或改出涡环状态？在操纵驾驶杆没有异常感觉时这种措施对改出涡环最为有效，损失高度的较少。Thismeasureismosteffectiveinrecoveringthevortexringwhenthereisnounusualfeelfromthecontrolstick,withlesslossofaltitude.活动3：如何预防或改出涡环状态？如果操纵效能已降低或失效，推杆也无法增大前飞速度，则应迅速地下放总距杆，增大下降率，使自下而上的相对气流速度增大，把绕着旋翼转动的环流向旋翼上方吹掉。Ifthecontroleffectivenesshasbeenreducedordisabledandthestickcannotincreaseforwardflightspeed,thecollectivepitchstickshouldberapidlyloweredtoincreasetherateofdescentsothattherelativeairflowvelocityfrombottomtotopincreases,blowingthecirculationaroundtherotorupabovetherotor.活动3：如何预防或改出涡环状态？然后再推驾驶杆增大前飞速度，改出涡环状态。这种方法损失高度较多，只有在高度较高或迫不得已时才采用。Thenpushthestickagaintoincreaseforwardflightspeed,changingoutofvortexringstatus.Thismethodlosesmuchaltitudeandisonlyusedwhenaltitudeishighornecessitated.Summary总结01什么是直升机涡环状态？Whatisahelicoptervortexringstatus?任务三：理解直升机涡环状态Understandhelicoptervortexringstatus02涡环状态的形成场景Scenesoftheformationofvortexringstates03如何预防或改出涡环状态？Howtopreventorchangeoutofvortexringstatus?Thinking思考尾桨涡环失效的原因与旋翼类似，思考并试着画出尾桨失效的过程图。模块九：直升机特殊飞行Learnabouthelicopterspecialflight任务三：理解直升机尾桨失效Understandhelicoptertailrotoreffectiveness直升机空气动力学与飞行原理Helicopteraerodynamicsandprinciplesofflight活动1：什么是直升机尾桨失效？01.PARTONEWhatisalossofhelicoptertailrotoreffectiveness?活动1：什么是直升机尾桨失效？Tounderstandwhatisalossofhelicoptertailrotoreffectiveness,wemustfirstknowwhatthetailrotordoestothehelicopter.要了解什么是直升机的尾桨失效，我们就必须先要知道尾桨对直升机的作用。活动1：什么是直升机尾桨失效？Theoriginalhelicopterdesignshadonlyonerotatingmainrotorusedtoprovidelift,butinordertocontrolflightdirectionandstability,designersbeganexperimentingwithaddingdifferentformsoftailstabilizers.Theadventofthetailrotorsolvedthisproblem.最初的直升机设计中只有一个旋转的主旋翼用来提供升力，但为了控制飞行方向和稳定性，设计者开始尝试加装不同形式的尾部稳定器。尾桨的出现解决了这一问题。活动1：什么是直升机尾桨失效？最早的尾桨通常是固定式的，位于直升机尾部，用来稳定方向和维持平衡。后来，随着直升机飞行速度的逐渐提高，固定式尾桨不能很好地满足空气动力学需求。Theearliesttailrotorwasusuallyfixedandlocatedatthetailofthehelicoptertostabilizethedirectionandmaintainbalance.Later,asthehelicopter'sflightspeedgraduallyincreased,thefixedtailrotorcouldnotmeettheaerodynamicrequirementswell.活动1：什么是直升机尾桨失效？因此可变尾桨应运而生。这种尾桨可以调节桨叶倾角，以保证在各种速度和飞行角度下，始终能够提供足够的稳定性和操纵性。Thusthevariabletailrotorwasborn.Thistailrotoradjuststheinclinationofthebladestoensurethatadequatestabilityandmaneuverabilityarealwaysprovidedatallspeedsandflightangles.(1)Thepullingforce(orthrust)formedbythetailrotorformsadeflectionmomenttobalancethereactionmomentoftherotor.活动1：什么是直升机尾桨失效？01.尾桨形成的拉力(或推力)形成偏转力矩，用以平衡旋翼的反作用力矩。尾桨的作用Theroleofthetailrotorcanbesummarizedinthefollowingthreepoints:(2)Bychangingthetension(orthrust)ofthetailrotor,theyawcontrolofthehelicopterisachieved,andtherotatingtailrotoractsastheverticalstabilizerofthehelicopter,improvingitsdirectionalstability.活动1：什么是直升机尾桨失效？02.通过变距改变尾桨的拉力(或推力)而实现直升机的偏航操纵，而且旋转的尾桨相当于直升机的垂直安定面，改善直升机的方向稳定性。尾桨的作用Theroleofthetailrotorcanbesummarizedinthefollowingthreepoints:(3)Insomehelicopters,thetailrotorisinclinedupwardatanangletoprovidepartialliftandtoadjustthehelicopter'scenterofgravity.活动1：什么是直升机尾桨失效？03.某些直升机的尾轴向上斜置一个角度，可以提供部分升力，也可以调节直升机的重心范围。尾桨的作用Theroleofthetailrotorcanbesummarizedinthefollowingthreepoints:中国直-9直升机的“涵道风扇”尾桨是中国自主设计和研发的尖端航空技术之一，优点在于尾桨占用空间小，气动力效率高，尾桨不易为外物所伤。The"culvertfan"tailrotorofChina'sZ-9helicopterisoneofthecutting-edgeaeronauticaltechnologiesindependentlydesignedanddevelopedbyChina,withtheadvantagesthatthetailrotortakesuplittlespace,hashighaerodynamicefficiencyandisnoteasytobeinjuredbyexternalobjects.活动1：什么是直升机尾桨失效？活动1：什么是直升机尾桨失效？而且由于涵道尾桨空气阻力小，因此速度比普通直升机要快。是目前批量生产的飞行速度最快的直升机。Andbecausetheculverttailrotorhaslessairresistance,itisfasterthanordinaryhelicopters.Itisthefastestflyinghelicoptercurrentlyinmassproduction.活动1：什么是直升机尾桨失效？作为中国第一种完全由自主设计和研发的直升机，直-9直升机已经成为中国军方和民用用户的主力机型之一，这种尾桨不仅仅是技术上的突破，更体现了中国航空工业的成就和民族自豪感。TheZ-9helicopterhasbecomeoneofthemainmodelsfortheChinesemilitaryandcivilianusers.Thistailrotorisnotonlyatechnologicalbreakthrough,butalsoreflectstheachievementsofChina'saerospaceindustryandnationalpride.活动1：什么是直升机尾桨失效？直升机尾桨失效，缩写为LTE,也称为丧失尾桨效应，是近年来造成直升机失控事故的一个重要原因。Lossofhelicoptertailrotoreffectiveness,abbreviatedLTE,alsoknownaslossoftailrotoreffect,hasbeenamajorcauseofhelicopterloss-of-controlaccidentsinrecentyears.活动1：什么是直升机尾桨失效？这是直升机在最后进近着陆或贴近地面飞行时的低高度、低空速飞行状态下发生的紧急情况，直升机会发生非指令的快速偏转，并且不会自动改出。Thisisanemergencysituationthatoccurswhenthehelicopterisinalowaltitude,lowairspeedflightstateonfinalapproachtolandingorflyingclosetotheground,wherethehelicopterundergoesanuncommanded,rapiddeflectionanddoesnotautomaticallychangeout.活动1：什么是直升机尾桨失效？在多数情况下，飞行员不当或较迟的修正措施可能加剧不可控制的偏转，导致直升机失去控制。所以，飞行员必须能预见尾桨失效并及时改出。Inmostcases,improperorlatecorrectiveactionbythepilotcanexacerbateuncontrollabledeflectionsandresultinlossofcontrolofthehelicopter.Therefore,pilotsmustbeabletoanticipatetailrotorfailureandchangeoutinatimelymanner.活动1：什么是直升机尾桨失效？尾桨失效现象与直升机的机械系统没有联系，旋翼旋转时产生的桨尖涡流以及自然风都会对尾桨拉力产生影响，尾桨不能提供适当的拉力保持航向。Thephenomenonoftailrotorfailureisnotlinkedtothemechanicalsystemofthehelicopter;therotortipvorticesgeneratedbytherotorrotationaswellasthenaturalwindshaveaneffectonthetailrotorpull,andthetailrotorisnotabletoprovidetheproperpulltomaintaintheheading.活动1：什么是直升机尾桨失效？所有单旋翼带尾桨直升机在悬停时受到风的影响，或高高度小速度飞行情况下都有可能发生尾桨失效现象。Allsingle-rotorhelicopterswithtailrotoraresubjecttotailrotorfailurewhenhoveringundertheinfluenceofwind,orwhenflyingathighaltitudesandlowspeeds.活动2：什么情况下可能会发生LTE？02.PARTTWOWhenisLTElikelytooccur?活动2：什么情况下可能会发生LTE？大量的飞行和风洞试验表明，有3种相对风结合直升机特性单独或综合作用，可能会使直升机产生LTE现象。Numerousflightandwindtunneltestshaveshownthattherearethreetypesofrelativewindscombinedwithhelicoptercharacteristicsthat,aloneorincombination,maycausethehelicoptertoproduceLTEphenomena.活动2：什么情况下可能会发生LTE？Thewindisblowingfromtheleftfront,blowingtherotorbladetipvortexintothetailrotor,makingthetailrotorworkinanextremelyturbulentenvironment.Atthispoint,therelativewindiswithintherotorbladetipinterferencezone.（一）风从左前方吹来，将旋翼桨尖涡吹进尾桨，使尾桨工作在极度的紊流环境中。此时，相对风处在旋翼桨尖干扰区内。右旋旋翼直升机右转弯时，为了保持固定的转弯角速度，应该蹬右舵减小尾桨拉力，以保持相同的偏转速率。Whenarightrotorhelicopterturnsright,inordertomaintainafixedangularrateofturn,therightruddershouldbestrokedtoreducethetailrotorpullinordertomaintainthesamerateofdeflection.活动2：什么情况下可能会发生LTE？活动2：什么情况下可能会发生LTE？当旋翼桨尖涡通过尾桨时，尾桨进入旋翼桨尖涡干扰区域，尾桨桨叶迎角减小，导致尾桨拉力减小，直升机将加速右转。Astherotorbladetipvortexpassesoverthetailrotor,thetailrotorenterstherotorbladevortexinterferenceregionandthetailrotorbladeangleofapproachdecreases,resultinginadecreaseintailrotorpullandthehelicopterwillaccelerateintoarightturn.活动2：什么情况下可能会发生LTE？尾桨拉力的减小是突然发生的，如果不及时修正，会发展成为不可控制的绕轴快速旋转，最终导致LTE。Thereductionintailrotorpulloccurssuddenlyand,ifnotcorrectedintime,candevelopintoanuncontrollablerapidrotationaroundtheshaft,eventuallyleadingtoLTE.活动2：什么情况下可能会发生LTE？Whentherelativewindisinthewindvaneeffectzone,therelativewindwillcausethehelicoptertowindvane,thenosewillturntothewindwarddirection,andifnocorrectionismade,thehelicopterwillautomaticallyrotateslowly,thedirectionofwhichdependsonthewinddirection.（二）当相对风处在风标效应区内，相对风会使直升机产生风标效应，机头将转向迎风方向，如果不进行修正，直升机将会自动缓慢地旋转，其方向取决于风向。活动2：什么情况下可能会发生LTE？如果飞行员允许直升机以一定的角速度旋转，尾部进入此区域，则偏航角速度会突然增加。Ifthepilotallowsthehelicoptertorotateatacertainangularvelocitywiththetailenteringthisarea,theyawangularvelocitywillsuddenlyincrease.为了防止直升机在这种顺风时发生LTE,飞行时必须密切注意直升机的状态，主动控制偏转速率，并集中注意力驾驶直升机。

TopreventthehelicopterfromLTEinthisdownwind,itisimportanttoflythehelicopterwithcloseattentiontothehelicopter'scondition,activelycontroltheyawrate,andconcentrateonflyingthehelicopter.活动2：什么情况下可能会发生LTE？活动2：什么情况下可能会发生LTE？Ifthewindisblowingfrom210°~330°,thewindwillcausethetailrotortoproduceavortexringstate.Atthistime,thetailrotorisinachangingandunstableflowfield,causingthetailrotorpullingforcetooscillate.（三）如