近地警告系統（GPWS）CFIT（可控飛行撞地）CFIT:Controlledflightintoterrain.為民航兩大主要航空事故之一（ALA：

ApproachandLanding），為一架飛機由機師正常控制，但因為一些失誤而撞上地面、阻礙物或水面墜毀。根據國際民航組織的統計，可控飛行撞地是加裝GPWS之前商用噴氣飛機機體損毀事故和人員死亡事故的元兇。1974年，FAA開始對在美國空域飛行的航班上的GPWS進行強制安裝要求（Honeywell），此后CFIT事故急劇減少。1985年后，CFIT事故每年僅發生1到2次，而強制要求安裝前每年發生7到8次。目前，全球幾乎所有的商用噴氣飛機均裝備GPWS。

GPWSisasystemdevelopedtohelppreventCFITaccidents.GPWS定義：地面迫近警告系統（GPWS,GroundProximityWarningSystem），又稱近地警告系統，是防止飛機因為離地過近而發生事故的系統，與TCAS搭配成為保護飛航安全的兩大防線。原理：GPWS在起飛開始到降落地面為止，持續監視飛機離地高度，利用無線電高度表獲得離地高度，并且以電腦計算出飛機的飛行趨勢，若有危險時會以視覺與語音警告飛行員采取避險措施。EGPWSEnhancedGroundProximityWarningSystems

(EGPWS),alsocalled

TerrainAwarenessWarningSystems(TAWS).AlimitationofGPWSisthefactthatwithradaraltimeterinformationtheaircraftisonlycapableofseeingterraindirectlybelow.Inthecaseofrapidlyrisingterrainitmaynotreactquickenoughtoissueawarningintime.EGPWScorrectsthisproblembyintegratinganaircraftnavigationalsourceintothesystem.GPSpositioninconjunctionwithaterraindatabaseisusedtohelppredictterrainconflict.Honeywe11公司在原有GPWS基礎上，開發出新型增強型近地警告計算機系統，該系統不僅增加了警告時間，還提供非常直觀的地形顯示，方便機組發現潛在的危險地形狀況，避免CFIT事故的發生。HOWITWORKSGPWS是當航機在異常接近地障的狀況下,使用語音,燈號以及在螢幕顯示警告文字來警告飛行員.這套系統只有在RA(RadioAltitude)2450尺以下才會作用啟動.

TheheartoftheGPWSisacomputerprocessorwhichwhichcananalyzethedatafrom:Radaraltimeter（雷達高度計）Airdatacomputer（大氣數據計算機）UHFNavreceiver（Ultra-highfrequency導航接收機）Gearandflapindicatingsystem（起落架和襟翼指示系統）Rollattitudeinputsensor（滾動姿態輸入傳感器）Thecomputeranalyzesanumberofparametersincludingaircraftconfiguration,speed,proximitytoterrain,anddescentrateinordertoissueappropriatewarnings.EnhancedGPWSFeaturesInadditiontoretainingcurrentGPWSalertingfunctions,theEGPWSofferstwonewmajorfeatures:Look-aheadterrainalerting.

Terraindisplay.

EGPWS:Look-aheadTerrainAlertingTheEGPWSprovidescaution-and–warning-levelalertstotheflightcrewaboutpotentialterrainconflictsearlierthanbasicGPWS.ThealertsarebasedprimarilyontheairplanepositionandbarometricaltitudeinformationpassedtotheEGPWS.Eitheraflightmanagementsystem(FMS)orglobalpositioningsystem(GPS)canprovideairplaneposition(latitudeandlongitude)totheEGPWS.Thelook-aheaddistancevariesmainlywithgroundspeed,Thelook-aheadcautionalertisprovidedapproximately40to60secondsbeforeapotentialterrainconflict,andthelook-aheadwarningalertisprovidedapproximately20to30secondsbeforesuchaconflict.Thealtitudeoffsetisnormally700feet(213m)belowtheairplane.Thepurposeoftheoffsetistoprovideterrainalertingwhentheairplanehaslessthanthenormalterrainclearance.EGPWS:

TerrainDisplayTheEGPWSterraindisplayisdesignedtoincreaseflightcrewawarenessofthesurroundingterrainandtopotentiallyavoidterrainconflictsentirely.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)belowToreduceclutteronthedisplay,anyterrainmorethan2,000feet(610m)belowtheairplaneisnotdisplayed,andinsteadremainsthebackgroundcolorofblack.Becausetheterraincolorsaredisplayedrelativetothecurrentairplanealtitude,thecolorswillchangeastheairplaneclimbsordescends.InthoseareasoftheworldforwhichtheEGPWSterraindatabasedoesnotyetcontainterraindata,adottedmagentapatternwillshowonthedisplay.EGPWS:

TerrainDisplayReferencealtitudePeakdisplayThefollowingimageillustratesthePeaksdisplayatahighrelativealtitude.ThefollowingimageillustratesthePeaksdisplayatalowrelativealtitude.如何發出警告

EGPWS可以向機組提供警戒或警告信息。當前飛行狀況導致EGPWS警戒或警告啟動時，無論機組是否選擇，地形圖將強制性的自動顯示在飛行儀表上。在EGPWS中，計算機沿著飛機的預定航跡連續搜索地形數據庫，這樣可使系統具有虛擬的前視能力。若飛機正在下降，計算機會沿下滑航跡進行搜索；若飛機正在轉彎，則沿轉彎航跡搜索。如果EGPWS認為飛機的航跡在某處與地形太近，它會提前一分鐘以上發出音頻和視頻告警信號。當EGPWS系統發出告警時，在飛行儀表上將用彩色固定方塊來加以強調，表示會引發危險的地形，同時還伴隨有相應的音響告警。固定的紅色方塊表示地形處在30秒的飛行時間范圍內，要求機組立即執行避開地形機動程序；而固定的黃色方塊則表示地形處在大約30到60秒的飛行時間范圍內，要求機組立即檢查飛行軌跡按需修正，并執行相應地形機動程序。

OperationmodeMode1:ExcessiveDescentRate(過度的下降速率)。（"SINKRATE""PULLUP"）Mode2:ExcessiveClosuretoTerrain(過度的地障接近率)。（"TERRAIN...TERRAIN""PULLUP"）Mode3:AltitudeLossAfterTakeoff(在航機起飛（Takeoff）或重飛（Goaround）爬升時航機高度值過度下降(Altitudeloss))。（"DON'TSINK"）Mode4:UnsafeTerrainClearance(與地障的間距不足)（未放下起落架或襟翼小于30度等）。（"TOOLOW-TERRAIN""TOOLOW-GEAR""TOOLOW-FLAPS"）Mode5:ExcessiveDeviationBelowGlideslope(儀器降落時與下滑道（Glideslope）的誤差過大)。("GLIDESLOPE")Mode6:AdvisoryCallouts(正常下降時的提醒)。(“BankAngle”

“FiveHundred”

“Minimums”)Mode7:WindshearAlerting(當飛機遭受風切變警訊)。(“Caution,Windshear”

“Windshear,Windshear,Windshear”)OperationmodeMode1:ExcessiveDescentRate(過度的下降速率)OperationmodeMode2:ExcessiveClosuretoTerrain(過度的地障接近率)OperationmodeMode3:AltitudeLossAfterTakeoff(在航機起飛（Takeoff）或重飛（Goaround）爬升時航機高度值過度下降(Altitudeloss))OperationmodeMode4:UnsafeTerrainClearance(與地障的間距不足)（未放下起落架或襟翼小于30度等）OperationmodeMode5:ExcessiveDeviationBelowGlideslope(儀器降落時與下滑道（Glideslope）的誤差過大)OperationmodeMode6:AdvisoryCallouts(正常下降時的提醒)calloutswouldbemadebythepilotnotflying(PNF).TerrainClearanceFloor(TCF)TheTerrainClearanceFloor(地形凈空基底或地形凈空平面)function(enabledwithTAD)enhancesthebasicGPWSModesbyalertingthepilotofdescentbelowadefined"TerrainClearanceFloor"regardlessoftheaircraftconfiguration.TheTCFalertisafunctionoftheaircraft'sRadioAltitudeanddistancerelativetothecentreofthenearestordestinationrunwayincludedinthedatabase.TCFenvelopeRunwayFieldClearanceFloor(RFCF)跑道高于周圍地形的機場。ARFCFfeatureissimilartotheTCFfeatureexceptthatRFCFisbasedonthecurrentaircraftpositionandheightabovethedestinationrunway,usingGeometricAltitude(