近地警告系统

近地警告系统（GPWS）CFIT（可控飞行撞地）CFIT:Controlledflightintoterrain.为民航两大主要航空事故之一（ALA：ApproachandLanding），为一架飞机由机师正常控制，但因为一些失误而撞上地面、阻碍物或水面坠毁。根据国际民航组织的统计，可控飞行撞地是加装GPWS之前商用喷气飞机机体损毁事故和人员死亡事故的元凶。1974年，FAA开始对在美国空域飞行的航班上的GPWS进行强制安装要求（Honeywell），此后CFIT事故急剧减少。1985年后，CFIT事故每年仅发生1到2次，而强制要求安装前每年发生7到8次。目前，全球几乎所有的商用喷气飞机均装备GPWS。GPWSisasystemdevelopedtohelppreventCFITaccidents.GPWS定义：地面迫近警告系统（GPWS,GroundProximityWarningSystem），又称近地警告系统，是防止飞机因为离地过近而发生事故的系统，与TCAS搭配成为保护飞航安全的两大防线。原理：GPWS在起飞开始到降落地面为止，持续监视飞机离地高度，利用无线电高度表获得离地高度，并且以电脑计算出飞机的飞行趋势，若有危险时会以视觉与语音警告飞行员采取避险措施。EGPWSEnhancedGroundProximityWarningSystems(EGPWS),alsocalledTerrainAwarenessWarningSystems(TAWS).AlimitationofGPWSisthefactthatwithradaraltimeterinformationtheaircraftisonlycapableofseeingterraindirectlybelow.Inthecaseofrapidlyrisingterrainitmaynotreactquickenoughtoissueawarningintime.EGPWScorrectsthisproblembyintegratinganaircraftnavigationalsourceintothesystem.GPSpositioninconjunctionwithaterraindatabaseisusedtohelppredictterrainconflict.Honeywe11公司在原有GPWS基础上，开发出新型增强型近地警告计算机系统，该系统不仅增加了警告时间，还提供非常直观的地形显示，方便机组发现潜在的危险地形状况，避免CFIT事故的发生。HOWITWORKSGPWS是当航机在异常接近地障的状况下,使用语音,灯号以及在萤幕显示警告文字来警告飞行员.这套系统只有在RA(RadioAltitude)2450尺以下才会作用启动.TheheartoftheGPWSisacomputerprocessorwhichwhichcananalyzethedatafrom:Radaraltimeter（雷达高度计）Airdatacomputer（大气数据计算机）UHFNavreceiver（Ultra-highfrequency导航接收机）Gearandflapindicatingsystem（起落架和襟翼指示系统）Rollattitudeinputsensor（滚动姿态输入传感器）Thecomputeranalyzesanumberofparametersincludingaircraftconfiguration,speed,proximitytoterrain,anddescentrateinordertoissueappropriatewarnings.EnhancedGPWSFeaturesInadditiontoretainingcurrentGPWSalertingfunctions,theEGPWSofferstwonewmajorfeatures:Look-aheadterrainalerting.Terraindisplay.EGPWS:Look-aheadTerrainAlertingTheEGPWSprovidescaution-and–warning-levelalertstotheflightcrewaboutpotentialterrainconflictsearlierthanbasicGPWS.ThealertsarebasedprimarilyontheairplanepositionandbarometricaltitudeinformationpassedtotheEGPWS.Eitheraflightmanagementsystem(FMS)orglobalpositioningsystem(GPS)canprovideairplaneposition(latitudeandlongitude)totheEGPWS.Thelook-aheaddistancevariesmainlywithgroundspeed,Thelook-aheadcautionalertisprovidedapproximately40to60secondsbeforeapotentialterrainconflict,andthelook-aheadwarningalertisprovidedapproximately20to30secondsbeforesuchaconflict.Thealtitudeoffsetisnormally700feet(213m)belowtheairplane.Thepurposeoftheoffsetistoprovideterrainalertingwhentheairplanehaslessthanthenormalterrainclearance.EGPWS:TerrainDisplayTheEGPWSterraindisplayisdesignedtoincreaseflightcrewawarenessofthesurroundingterrainandtopotentiallyavoidterrainconflictsentirely.Theterraindisplaycanbeselectedmanuallybytheflightcrewordisplayedautomaticallywhenalook-aheadcautionorwarningalertactivates.TheterrainisdisplayedontheElectronicHorizontalSituationIndicator(EHSI)ornavigationdisplay(ND),oronadedicatedweatherradardisplayinflightdeckswithoutmapdisplays.Theterrainisshownonthedisplayindottedpatternsofred,amber,andgreen,withthecolorsindicatingtheheightoftheterrainrelativetothecurrentairplanealtitude.--dottedred:2,000feet(610m)abovetheairplanealtitude--dottedamber:from500feet(152m)belowthecurrentairplanealtitudeto2,000feet(610m)above--dottedgreen:500feet(152m)belowToreduceclutteronthedisplay,anyterrainmorethan2,000feet(610m)belowtheairplaneisnotdisplayed,andinsteadremainsthebackgroundcolorofblack.Becausetheterraincolorsaredisplayedrelativetothecurrentairplanealtitude,thecolorswillchangeastheairplaneclimbsordescends.InthoseareasoftheworldforwhichtheEGPWSterraindatabasedoesnotyetcontainterraindata,adottedmagentapatternwillshowonthedisplay.EGPWS:TerrainDisplayReferencealtitudePeakdisplayThefollowingimageillustratesthePeaksdisplayatahighrelativealtitude.ThefollowingimageillustratesthePeaksdisplayatalowrelativealtitude.如何发出警告EGPWS可以向机组提供警戒或警告信息。当前飞行状况导致EGPWS警戒或警告启动时，无论机组是否选择，地形图将强制性的自动显示在飞行仪表上。在EGPWS中，计算机沿着飞机的预定航迹连续搜索地形数据库，这样可使系统具有虚拟的前视能力。若飞机正在下降，计算机会沿下滑航迹进行搜索；若飞机正在转弯，则沿转弯航迹搜索。如果EGPWS认为飞机的航迹在某处与地形太近，它会提前一分钟以上发出音频和视频告警信号。当EGPWS系统发出告警时，在飞行仪表上将用彩色固定方块来加以强调，表示会引发危险的地形，同时还伴随有相应的音响告警。固定的红色方块表示地形处在30秒的飞行时间范围内，要求机组立即执行避开地形机动程序；而固定的黄色方块则表示地形处在大约30到60秒的飞行时间范围内，要求机组立即检查飞行轨迹按需修正，并执行相应地形机动程序。OperationmodeMode1:ExcessiveDescentRate(过度的下降速率)。（SINKRATEPULLUP）Mode2:ExcessiveClosuretoTerrain(过度的地障接近率)。（TERRAIN...TERRAINPULLUP）Mode3:AltitudeLossAfterTakeoff(在航机起飞（Takeoff）或重飞（Goaround）爬升时航机高度值过度下降(Altitudeloss))。（DON'TSINK）Mode4:UnsafeTerrainClearance(与地障的间距不足)（未放下起落架或襟翼小于30度等）。（TOOLOW-TERRAINTOOLOW-GEARTOOLOW-FLAPS）Mode5:ExcessiveDeviationBelowGlideslope(仪器降落时与下滑道（Glideslope）的误差过大)。(GLIDESLOPE)Mode6:AdvisoryCallouts(正常下降时的提醒)。(“BankAngle”“FiveHundred”“Minimums”)Mode7:WindshearAlerting(当飞机遭受风切变警讯)。(“Caution,Windshear”“Windshear,Windshear,Windshear”)OperationmodeMode1:ExcessiveDescentRate(过度的下降速率)OperationmodeMode2:ExcessiveClosuretoTerrain(过度的地障接近率)OperationmodeMode3:AltitudeLossAfterTakeoff(在航机起飞（Takeoff）或重飞（Goaround）爬升时航机高度值过度下降(Altitudeloss))OperationmodeMode4:UnsafeTerrainClearance(与地障的间距不足)（未放下起落架或襟翼小于30度等）OperationmodeMode5: