A320前轮转弯系统介绍及维护

A320前轮转弯系统介绍及维护一车间李辉一、背景介绍Thesteeringsystemusesthegreenoryellowhydraulicsystemtooperateasteeringactuatingcylinder,whichchangesthedirectionoftheNLGwheels.飞机在地面滑行时的方向控制，几乎完全依赖于前轮转弯系统NWS来操作完成。如果前轮转弯系统出现故障，机组将无法掌控飞机的滑跑方向，从而使飞机偏离或冲出跑道、滑行道，轻则损伤飞机设备，严重的甚至会造成人员的重大伤亡。因此，对于前轮转弯系统相关故障，必须按手册谨慎处置。JetblueAirbusperformsalowpassfortheLGBtowerforanosegearinspection,andasyoucanseethenosegearisina90-degreeposition.Followingtheflyby,theaircraftspentthenext2hoursflyingoverthePacificOceanjustoffLongBeachburningfuelbeforedivertingtoLAXforanemergencylanding,whichhappilywasasuccesfulonewithoutinjuries.JetblueA320-232(N536JB)前起落架减震支柱上支撑防转凸耳损伤被剪切断裂,导致前轮空中偏置90度，于LosAngelesairport(LAX)执行应急着陆。JetBlue292BUR-JFKmakesitsemergencylandingatLAX.Thefrontgearwasturnedperpendiculartotherunwaycausingthesparksandsmoke.LTEInternationalAirwaysA320-214在着陆滑跑过程中因前轮转弯系统故障，导致偏离跑道，前轮陷入跑道旁边的草地。二、系统介绍SYSTEMOVERVIEWThesteeringsystemreceiveshydraulicpressureinthefollowingconditions:-A/SKID&N/WSTeeRinGswitchisinONposition,-towingcontrolleverisinnormalposition,-atleastoneENGMASTERswitchisON,-aircraftisonground.ThesteeringsystemiscontrolledbytheBSCU,whichreceivesorderfrom:-thesteeringhandwheels(ordersaddedalgebraically),-therudderpedals,-theautopilot.前轮转弯角度限制HandwheelsDuringtaxi,andmoregenerallyatlowspeed,throughactiononahandwheel.Therearetwoidenticalhandwheels:onefortheCaptain,onefortheFirstOfficer.Intheeventofsimultaneousoperation,theordersthatthehandwheelsgivearealgebraicallyadded.Themaximumtravelofthewheelsisplusorminus74deg.Themaximumcorrespondingtravelofthehandwheelisplusorminus75deg.Thelawbetweenthesetwotravelsisnotlinear.Thesteeringangleislimitedasafunctionoftheaircraftspeed.（手轮偏转角度与前轮转弯角度比例关系）（手轮操作时前轮转弯角度与飞机速度的限制关系）20KTS以内，最大行程操作速度高于70KTS，使用手轮转弯无效RudderpedalsDuringtakeofforlanding,andmoregenerallyathighspeed：-eitherthroughactionoftheCaptain(orFirstOfficer)ontherudderpedals,-orautomaticallythroughtheautopilot(yawcontrol).Intheeventofsimultaneousoperation,theordersthatthehandwheelsandpedalsgivearealgebraicallyadded.PEDALSDISC按钮可在以下情况脱开脚蹬对前轮转弯的控制：－Duringruddergroundcheck.－Therunwayisicy.Pilotcandisconnectthecontrolthroughthepedalsfromthesteeringcontrol.Whentheaircraftspeedisabove130knots,thesteeringisnotavailable（脚蹬操作时前轮转弯角度与飞机速度的限制关系）NoseWheelSteeringServo-Control(6GC)enhancedtype图示为增强型A320系列飞机，区别在于选择活门位置与classic不同,液压使用的是黄系统NoseWheelSteeringServo-Control(6GC)classictype传统型的6GC将选择活门作为部件嵌入到整体中。液压选用的是绿系统。NoseWheelSteeringServo-Control(6GC)SelectorvalveBleedscrewAnti-shimmyaccumulatorServovalveNoseWheelSteeringServo-Control(6GC)maincomponents－Anelectrically-operatedselectorvalveanditsslavedvalve.Whentheselectorvalveisenergized,thepressureisappliedtotheservovalve.－Aservovalveofthedeflection-jettype,equippedwithaLVDTsensorwhichdetectsthepositionoftheslidevalve.－Anadjustablediaphragmlocatedoneachoutputlineoftheservovalve,thisdiaphragmisusedtoadjusttheflowtoeachactuatingcylinderchamberandconsequentlythewheelsteeringspeed.－Aby-passvalvewhichinterconnectsthetwochambersofthesteeringcylinderintheeventofhydraulicsystemdepressurization.－Ananti-shimmyaccumulatorwithabuilt-inpressure-reliefvalve,Itcansupplyfluidpressurizedto15barsincaseofcavitationinonechamberofthecylinder,initiatedbytheshimmy.－Ascrewforthebleedingand/ordepressurizationofthehydraulicblock.对于传统型A320飞机，由于前轮转弯系统使用的是来自前起落架舱门关闭油路的绿系统液压压力，因此，在飞机执行重力放起落架的程序后，前轮转弯系统将无法工作，需用拖车拖回停机坪。使用重力放起落架的英航A320-214在近进阶段NoseWheelSteeringFeedbackSensor(3GC,4GC)P/N:E21336000P/N:C24763000(ONA/C001-013)NoseWheelSteeringFeedbackSensor(3GC,4GC)TwoidenticalRVDTsensorsgivethepositionoftherotatingtube.TheRVDTsensorisdrivenbyareductiongearboxattachedtothelandinggearstrut.3GCispartoftheelectricalchannelofthesteeringcontrol,4GCispartofthemonitoringchannel.Thecontrolchannelactsontheservovalveasafunctionofthedifferenceinpositionbetweenthehandwheel(inthecockpit)andthewheels.Themonitoringchanneldeliversinasimilarmannerasignalwhichrepresentsthepositionoftheslidevalveintheservovalve.3GCforcontrol4GCformonitoringNWS系统工作原理swivelselectorvalveWhenthelandinggearstartstoretract,theswivelselectorvalvecutsthehydraulicpowersupplyandconnectsthehydraulicblocktothereservoirreturnline.旋转选择活门与前起落架收放支点同轴，前起放下使活门内部液压流向前轮转弯作动系统。steeringactuatingcylinder转弯作动筒内部为：活塞推动齿条与前起落架转动筒的半齿轮机构啮合作动，通过后部的上、下扭力臂驱动前起落架减震器完成转弯动作。anti-shimmyvalve减震支柱从前起落架内拔出后，可以看出前轮转弯作动筒驱动的是中间的旋转筒。前起落架减震支柱被拔出，扭力臂的下端仍然在位。三、维护要点1、关于3GC、4GC的维护由前面的介绍可知：3GC、4GC的反馈信号的准确性对整个转弯系统的工作起到了决定性的作用。针对机组反映的滑行中无法保持直线（偏左或偏右）的问题，在排除了侧风、道面状况、机轮状态以及机组操作方面的原因后，需要对3GC进行微调。调节或更换传感器，请严格遵守AMM程序！前轮转弯不当或系统故障将导致轮胎的过量磨损，甚至爆胎AMM手册关于前轮转弯0位的调节提供了9种程序，其主要区别就是采用了不同的基准参考数据和3GC、4GC调节工具：基准数据：1－RudderTrimAngleasReference2－NLGCenteringCamsasReference3－Nose-WheelAlignmentTool调节工具：ForP/NC24763000：F26630200或M46196-100＋F26792000ForP/NE21336000：F26792000AMM32-51-00-820-00x1、AdjustmentoftheN/WSZeroPositionwiththeAdjustingToolF26630200forA/CwithN/WSSensor(3GC,4GC)P/NC24763000,RudderTrimAngleasReference2、AdjustmentoftheN/WSZeroPositionwithAdjustingToolM46196-100forA/CwithN/WSSensor(3GC,4GC)P/NC24763000,R