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TheAirbusSafetyMagazineEditionJanuary2011SafetyIssue11CONTENT:qWhatisstallHowapilotshouldreactinfrontofastallsituationqMinimumcontrolspeedtestsonA380qRadioAltimetererroneousvaluesqAutomaticNAVengagementatGoAroundSafetyFirstTheAirbusSafetyMagazineFortheenhancementofsafeflightthroughincreasedknowledgeandcommunicationsSafetyFirstispublishedbytheFlightSafetyDepartmentofAir-bus.
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A380Waterpooltest2Issue11|JANUARY2011SafetyEditorialContentsForthoseofyouwhoknewYvesBenoist,itismysaddutytoinformyouthatYvespassedawaysuddenly,attheendofDecember.
YvesheldthepositionofVice-PresidentFlightSafetyatAirbusfor16years,beforeretiringin2004.
Throughoutmytimeworkingwithhim,hepassedonthreemainlessons:investigationsrequirerigor,thoroughtechnicalunderstandingandpatience.
Theselessonsremainvalidtoday,despitethegreaterchallengeimposedbytoday'senvironment.
Inadditiontothis,Yvesstressedtheimportanceofthedisseminationofinformationandsharingoflessonslearnt.
Thisledhim,in1994,tolaunchtheannualAirbusFlightSafetyConferenceaswellastheAirbusSafetyMagazine,HangarFlying(nowSafetyFirst),whicharestilltodaythemostvisiblepartofYves'heritage.
OurthoughtsatthistimearewithYves'family.
Ihavenodoubtyouwilljoinmeinappreciationofhisremarkableachievements.
Today,ourchallengeistobuilduponYves'legacy.
Letmewishyouahappynewyear,toyouandyourfamily.
YannickMALINGEChiefProductSafetyOfficerTheAirbusSafetyMagazineInformation4WhatisstallHowapilotshouldreactinfrontofastallsituation.
5JacquesRosayMinimumcontrolspeedtestsonA380.
11ClaudeLelaieRadioAltimetererroneousvalues.
15MarcBaillion/LorraineDeBaudusAutomaticNAVengagementatGoAround.
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19StéphaneGranger/EricJeanpierreYannickMALINGEChiefProductSafetyOfficer3Issue11|JANUARY2011TheAirbusSafetyMagazineMagazinedistributionIfyouwishtosubscribetoSafetyFirst,pleasefilloutthesubscrip-tionformthatyouwillfindattheendofthisissue.
Pleasenotethatthepapercopieswillonlybeforwardedtoprofes-sionaladdresses.
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Wewouldappreciatearticlesfromoperators,thatwecanpasstootheroperatorsthroughthemagazine.
IfyouhaveanyinputsthenpleasecontactNilsFayaudat:e-mail:nils.
fayaud@airbus.
comfax:+33(0)561934429TheformalinvitationswithinformationregardingregistrationandlogisticsandthepreliminaryagendahavebeensenttoourcustomersinDecember2010.
FollowingthesuccessfuleventinBrussels,inMarchofthisyear,wearepleasedtoannouncethatthe17thFlightSafetyConferencewilltakeplaceinRome,Italy,from21stto24thofMarch2011.
TheFlightSafetyConferenceprovidesanexcellentforumfortheexchangeofinformationbetweenAirbusandcustomers.
TheeventisadedicatedforumforallAirbusoperators.
Wedonotacceptoutsideparties.
Thisensuresthatwecanhaveanopendialoguetopromoteflightsafetyacrossthefleet.
Asalwayswewelcomepresentationsfromyou,theconferenceisaforumforeverybodytoshareinformation.
Ifyouhavesomethingyoubelievewillbenefitotheroperatorsand/orAirbusorneedadditionalinvitationsorinfor-mation,pleasecontactNuriaSolerat:e-mail:nuria.
soler@airbus.
comfax:+33(0)561934429SafetyInformationontheAirbuswebsitesOntheAirbusWorldwebsitewearebuildingupmoresafetyinformationforyoutouse.
ThepresentandpreviousissuesofSafetyFirstcanbeaccessedtointheFlightOperationsCommunity-Safe-tyandOperationalMaterialschapter-,athttps://w3.
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safety@airbus.
comNilsFayaudDirectorProductSafetyInformationNews4Issue11|JANUARY2011SafetyJacquesROSAYVPChiefTestPilotWhatisstallHowapilotshouldreactinfrontofastallsituation2.
TheliftAwinggeneratesaliftequalto1/2ρSVCl.
With:ρ=airdensityS=wingsurfacereferenceV=TrueAirSpeedCl=liftcoefficientofthewing1.
IntroductionTheworldwideairtransportfleethasrecentlyencounteredanumberofstallevents,whichindicatethatthisphenomenonmaynotbeprop-erlyunderstoodandmanagedintheaviationcommunity.
Asacon-sequence,themainaircraftmanu-facturershaveagreedtogethertoamendtheirstallproceduresandtoreinforcethetraining.
AworkinggroupgatheringAuthoritiesandaircraftmanufacturerswillpublishrecommendationsforharmonizedproceduresandappropriatetrain-ing.
Thisarticleaimsatremindingtheaerodynamicphenomenonas-sociatedtothestall,andtherecent-lypublishednewprocedures.
TheliftcoefficientincreasesasafunctionoftheAngleofAttack(AoA)uptoavalue,calledMaximumlift,whereitstartstodecrease.
AngleofAttackRelativewindLiftisfunctionofSpeedDensityWingareaAngleofAttackChordlineAngleofAttackLiftMaximumLiftForagivenconfiguration,agivenspeedandagivenaltitude,theliftisonlylinkedtotheAoA.
5Issue11|JANUARY2011TheAirbusSafetyMagazine3.
ThestallphenomenumThelinearpartofthecurvecorre-spondstoasteadyairflowaroundthewing.
WhentheAoAreachesthevalueofthemaximumCl,theairflowstartstoseparate.
CIAoALiftAngleofAttackCriticalAngleofAttackMaximumliftStalledNotstalled6°,steadyflowLiftAngleofAttackCriticalAngleofAttackMaximumliftStalledNotstalledseparatedpointstallpoint,maximumliftCIAoALiftAngleofAttackCriticalAngleofAttackMaximumliftStalledNotstalledseparatedflowCIAoABeyondthispoint,theliftdecreasesastheflowisseparatedfromthewingprofile.
Thewingisstalled.
Onthispicture(extractedfromavideofootage),theerraticpositionsoftheflowconesonthisA380wingduringastalltestshowthattheflowisseparated.
6Issue11|JANUARY2011Safety4.
SomeimportantthingstorememberaboutthestallqForagivenconfigurationandatagivenMachnumber,awingstallsatagivenAngleofAttack(AoA)calledAoASTALL.
WhentheMachnumberincreases,thevalueoftheAoASTALLdecreases.
qWhenapproachingtheAoASTALL,thewinggeneratesacer-tainlevelofbuffeting,whichtendstoincreaseinlevelathighMachnumber.
qWhentheAoAincreasesandap-proachestheAoASTALL,incer-taincases,aphenomenonofpitchupoccursasaresultofachangeinthedistributionoftheliftalongthewingspan.
Theeffectofthepitchupisaself-tendencyoftheaircrafttoincreaseitsAngleofAt-tackwithoutfurtherinputsontheelevators.
Generally,foragivenwing,thisphenomenonoccursatalowerAngleofAttackandismoreprominentwhentheMachnumberishigher.
qTheonlymeantocounterthepitchupistoapplyanosedownelevatorinput.
qWhentheaerodynamicflowonthewingisstalled,theonlypossi-blemeantorecoveranormalflowregimeistodecreasetheAoAatavaluelowerthantheAoASTALL.
qStallisanAoAproblemonly.
ItisNOTdirectlyaspeedissue.
Knowingthosetwolastcharacter-isticsisabsolutelyparamount,astheydictatetheonlypossiblewaytogetoutofastall.
5.
ProtectionsagainstthestallinnormallawonfbwaircraftInNORMALLAW,theElectronicFlightControlsSystem(EFCS)takesintoaccounttheactualAoAandlimitsittoavalue(AoAMAX)lowerthanAoASTALL(fig.
1).
TheEFCSadjuststheAoAMAXlimitationtoaccountforthereductionoftheAoASTALLwithincreasingMachnumber.
Equally,foragivenMachnumberandagivenAoA,theEFCStakesintoaccountthenaturalpitchupeffectofthewingforthisMachnumberandthisAoA,andappliesontheelevatorstheappro-priatelongitudinalpre-commandtocounteritseffect.
6.
ProtectionsagainstthestallinalternateanddirectlawonFBWandconven-tionalaircraftOnFBWaircraft,followingcer-tainmalfunctions,inparticularincaseofsensororcomputerfailure,theflightcontrolscannotensuretheprotectionsagainstthestall.
Dependingonthenatureofthefail-ure,theyreverttoALTERNATELAWortoDIRECTLAW.
Inbothcases,thepilothastoen-suretheprotectionagainstthestall,basedupontheauralStallWarning(SW),orastrongbuffetingwhich,ifencountered,isanindicationofanincipientstallcondition.
TheconventionalaircraftarepermanentlyinDIRECTLAW,andregardingthestallprotection,theyareinthesamesituationastheFBWaircraftinDIRECTLAW.
InbothALTERNATEandDIRECTLAW,theauralSWissetatavaluecalledAoAStallWarn-ing(AoASW),whichislowerthantheAoASTALL(fig.
2).
ThetriggeringoftheStallWarn-ingjustmeansthattheAoAhasreachedtheAoASW,whichisbydefinitionlowerthantheAoASTALL,andthattheAoAhastobereduced.
CIAoALiftAngleofAttackCriticalAngleofAttackMaximumliftStalledNotstalledAoAMAXLiftAngleofAttackCriticalAngleofAttackMaximumliftStalledNotstalledAoAStallWarningCIAoAFigure1InNORMALLAW,theEFCSlimitstheAoAtoavaluelowerthanAoASTALLFigure2InALTERNATEandDIRECTLAW,theauralStallWarningissetatavaluelowerthanAoASTALL7Issue11|JANUARY2011TheAirbusSafetyMagazineKnowingwhattheSWis,thereisnoreasontooverreacttoitstrigger-ing.
ItisabsolutelyessentialforthepilotstoknowthattheonsetoftheauralStallWarningdoesnotmeanthattheaircraftisstalling,thatthereisnoreasontobescared,andthatjustagentleandsmoothreac-tionisneeded.
ThevalueoftheAoASWdependsontheMachnumber.
AthighMachnumber,theAoASWissetatavaluesuchthatthewarningoccursjustbeforeencounteringthepitchupeffectandthebuffeting.
IftheanemometricinformationusedtosettheAoASWiserro-neous,theSWwillnotsoundattheproperAoA.
Inthatcase,asmentionedabove,theclueindicat-ingtheapproachofthestallisthestrongbuffeting.
Intheremainderofthisdocument,forthissitua-tion,"SW"mustbereadas"strongbuffeting".
7.
MargintotheStallWarningincruiseathighMachnumberandhighaltitudeTypically,incruiseathighMachnumberandhighaltitude,atorclosetothemaximumrecom-mendedFL,thereisasmallmar-ginbetweentheactualcruiseAoAandtheAoASTALL.
Hence,inALTERNATEorDIRECTLAW,themarginwiththeAoASWisevensmaller.
Theencounterofturbulencein-ducesquickvariationsoftheAoA.
Asaconsequence,whentheair-craftisflyingclosetothemaxi-mumrecommendedaltitude,itisnotunlikelythatturbulencemightinducetemporarypeaksofAoAgoingbeyondthevalueoftheAoASWleadingtointermittentonsetsofauralSW.
Equally,insimilarhighFLcruiseconditions,inparticularatturbulencespeed,ifthepilotmakessignificantlongitudinalinputs,itisnotunlikelythatitreachestheAoASWvalue.
Forthosereasons,wheninALTER-NATEorDIRECTLAW,itisrec-ommendedtoflyatacruiseflightlevellowerthanthemaximumrec-ommended.
A4,000ftmarginistobeconsidered.
Then,forthesamecruiseMachnumber,theIASwillbehigher,theAoAwillbelower,andthereforetheAoAmargintowardsAoASWwillbesignifi-cantlyincreased.
Inaddition,asinRVSMspacetheuseoftheAPismandatory,anyfailuresleadingtothelossoftheAPmandatestodescendbelowtheRVSMverticallimit.
8.
StallWarningandstallThetraditionalapproachtostalltrainingconsistedinacontrolleddecelerationtotheStallWarning,followedbyapowerrecoverywithminimumaltitudeloss.
Experienceshowsthatifthepilotisdeterminedtomaintainthealti-tude,thisproceduremayleadtothestall.
ApracticalexercisedoneinflightinDIRECTLAWonanA340-600andwellreproducedinthesimula-torconsistsinperformingalowalti-tudelevelflightdecelerationatidleuntiltheSWistriggered,andthentopushtheTHRleverstoTOGAwhilecontinuingtopullonthestickinor-dertomaintainthealtitude.
Theresultsofsuchamanoeuvreare:qIncleanconfiguration,evenifthepilotreactsimmediatelytotheSWbycommandingTOGA,whenthethrustactuallyreachesTOGA(20secondslater),theaircraftstalls.
qInapproachconfiguration,ifthepilotreactsimmediatelytotheSW,theaircraftreachesAoAstall-2°.
qInapproachconfiguration,ifthepilotreactswithadelayof2sec-ondstotheSW,theaircraftstalls.
ThisshowsthatincreasingthethrustattheSWinordertoincreasethespeedandhencetodecreasetheAOAisnottheproperreactioninmanycases(thiswillbedevelopedinthefollowingchapter).
Inaddition,itistobenoticedthat,athighaltitude,theeffectofthethrustincreaseonthespeedriseisveryslow,sothatthephenomenomdescribedaboveforthecleancon-figurationisexacerbated.
Obviously,suchaprocedureleadstopotentiallyunrecoverablesitu-ationsifitisappliedoncetheair-crafthasreachedtheaerodynamicstall(seenextchapter).
EvenifthetraditionalprocedurecanworkincertainconditionsifthepilotreactsimmediatelytotheSW,orifheisnottooadamantonkeepingthealtitude,themajoris-suecomesfromthefactthatoncetheStallWarningthresholdhasbeencrossed,itisdifficulttoknowiftheaircraftisstillapproachingtostalloralreadystalled.
Differencebetweenanapproachtostallandanactualstallisnoteasytodetermine,evenforspecialists.
Severalaccidentshappenedwherethe"approachtostall"procedurewasappliedwhentheaircraftwasactuallystalled.
Forthosereasons,thepilotsshouldreactthesamewayforboth"ap-proachtostall"and"stall"situations.
9.
HowtoreactWhatisparamountistodecreasetheAoA.
Thisisobtaineddirectlybydecreasingthepitchorder.
ThepitchcontrolisadirectAoAcommand(fig.
3).
TheAoAdecreasemaybeobtainedindirectlybyincreasingthespeed,butaddingthrustinordertoincreasethespeedleadstoaninitialadverselongitudinaleffect,whichtrendstoincreasefurthertheAoA(fig.
4).
Itisimportanttoknowthatifsuchathrustincreasewasappliedwhentheaircraftisalreadystalled,thelongitudinaleffectwouldbringtheaircraftfurtherintothestall,toasituationpossiblyunrecoverable.
Conversely,thefirsteffectofre-ducingthethrustistoreducetheAoA(fig.
5).
8Issue11|JANUARY2011SafetyInsummary:FIRST:TheAoAMUSTBERE-DUCED.
Ifanything,releasethebackpressureonstickorcolumnandapplyanosedownpitchinputuntiloutofstall(nolongerhavestallindications).
Incertaincases,anactioninthesamedirectiononthelongitudinaltrimmaybeneed-ed.
Don'tforgetthatthrusthasanadverseeffectonAoAforaircraftwithenginesbelowthewings.
SECOND:Whenthestallclueshavedisappeared,increasethespeedifneeded.
Progressivelyincreasethethrustwithcare,duetothethrustpitcheffect.
Inpractice,instraightflightwith-outstickinput,thefirstreactionwhentheSWistriggeredshouldbeRelativeairflowRelativeairflowThrustincreaseRelativeairflowThrustreductionFigure3PitchcontrolisadirectAoAcommandFigure4AddingthrustleadstoanincreaseinAoAFigure5ReducingthrustleadstoadecreaseinAoAtogentlypushonthesticksoastodecreasethepitchattitudebyabouttwoorthreedegreesinordertode-creasetheAoAbelowtheAoASW.
Duringmanoeuvres,thereductionoftheAoAisgenerallyobtainedjustbyreleasingthebackpressureonthestick;applyingaprogres-siveforwardstickinputsensuresaquickerreductionoftheAoA.
IftheSWsituationoccurswithhighthrust,inadditiontothestickreaction,reducingthethrustmaybenecessary.
10.
ProcedureAsananswertothestallsituation,aworkinggroupgatheringtheFAAandthemainaircraftmanufactur-ers,includingAirbus,ATR,Boeing,BombardierandEmbraer,havees-tablishedanewgenericproceduretitled"StallWarningorAerody-namicStallRecoveryProcedure"applicabletoallaircrafttypes.
Thisgenericprocedurewillbepub-lishedasanannextotheFAAAC120.
Thisnewprocedurehasbeenestab-lishedinthefollowingspirit:qOnesingleproceduretocoverALLstallconditionsqGetridofTOGAasfirstactionqFocusonAoAreduction.
9Issue11|JANUARY2011TheAirbusSafetyMagazineGenericStallWarningorAerodynamicStallRecoveryProcedureImmediatelydothefollowingatthefirstindicationofstall(buffet,stickshaker,stickpusher,orauralorvisualindication)duringanyflightphasesexceptatliftoff.
1.
Autopilotandautothrottle.
DisconnectRationale:Whilemaintainingtheattitudeoftheaircraft,disconnecttheautopilotandautothrottle.
Ensurethepitchattitudedoesnotchangeadverselywhendisconnectingtheautopilot.
Thismaybeveryim-portantinmis-trimsituations.
Manualcontrolisessentialtorecoveryinallsituations.
Leavingoneortheotherconnectedmayresultinin-advertentchangesoradjustmentsthatmaynotbeeasilyrecognizedorappropriate,especiallyduringhighworkloadsituations.
2.
a)Nosedownpitchcontrol…Applyuntiloutofstall(nolongerhavestallindications)b)Nosedownpitchtrim.
AsneededRationale:a)Thepriorityisreducingtheangleofattack.
Therehavebeennumeroussituationswhereflightcrewsdidnotprioritizethisandinsteadprioritizedpowerandmaintainingaltitude.
Thiswillalsoaddressautopilotinducedfullbacktrim.
b)Ifthecontrolcolumndoesnotprovidetheneededresponse,stabilizertrimmaybenecessary.
However,excessiveuseoftrimcanaggravatethecondition,ormayresultinlossofcontrolorinhighstructuralloads.
3.
Bank.
WingsLevelRationale:Thisorientatestheliftvectorforrecovery.
4.
Thrust.
AsNeededRationale:Duringastallrecovery,manytimesmaximumpowerisnotneeded.
Whenstalling,thethrustcanbeatidleorathighthrust,typicallyathighaltitude.
Therefore,thethrustistobeadjustedaccordinglyduringtherecovery.
Forenginesinstalledbelowthewing,applyingmaximumthrustcancreateastrongnoseuppitchingmoment,ifspeedislow.
Foraircraftwithenginesmountedabovethewings,thrustapplicationcreatesahelpfulpitchdowntendency.
Forpropellerdrivenaircraft,thrustapplicationenergizestheairflowaroundthewing,assistinginstallrecovery.
5.
SpeedBrakes.
RetractRationale:Thiswillimproveliftandstallmargin.
6.
Bank.
WingsLevelRationale:Applygentleactionforrecoverytoavoidsecond-arystallsthenreturntodesiredflightpath.
RevisionofAirbus'OperationaldocumentationAirbushasupdateditsoperationaldocumentationinordertoreflectthechangesintroducedbythenewgenericstallrecoveryprocedures.
Inordertoallowsimultaneousfleetwideintroduction,theprocedurewasprovidedviaTemporaryRevision.
ThisinformationwasprovidedtogetherwithanFCTMupdateadvancecopyandFOT999.
0044/10,onMay12,2010.
A300:A300FCOMvolume8GETemporaryRevisionnumber219-1A300FCOMvolume8PWTemporaryRevisionnumber051-1A300QRHTemporaryRevisionnumber076-1A300FFCC:A300FFCCFCOMvolume2TemporaryRevisionnumber052-1A300FFCCQRHTemporaryRevisionnumber025-1A300-600/A300-600F:A300-600/A300-600FFCOMvolume2TemporaryRevisionnumber002-2A300-600/A300-600FQRHTemporaryRevisionnumber217-1A310:A310FCOMvolume2TemporaryRevisionnumber004-2A310QRHTemporaryRevisionnumber224-1A318/319/320/321:FCOMvolume3TemporaryRevisionnumber323-1QRHTemporaryRevisionnumber727-1A330:FCOMvolume3TemporaryRevisionnumber552-1QRHTemporaryRevisionnumber353-1A340:FCOMvolume3TemporaryRevisionnumber512-1(A340-200/-300)FCOMvolume3TemporaryRevisionnumber513-1(A340-500/-600)QRHTemporaryRevisionnumber369-1A380:FCOMProcedures/Non-ECAMAbnormalandEmergencyProcedures/OperatingTechniques10Issue11|JANUARY2011SafetyClaudeLELAIESpecialAdvisortoCEOMinimumcontrolspeedtestsonA380Whentheaircrafthasanengineshutdownwiththe3othersatmaximumthrust,ithasatendencytoyawtowardthe"failed"engine.
Thepilotcandeflecttherudderandcreateayawmomentintheotherdirectioninordertomaintaintheheading.
However,whenthespeedisdecreasingtheenginescreatemoreorlessthesameyaw,buttheaerodynamicefficiencyofthefinandtherudderarereducing.
Atagivenspeed,withwingslevel,therudderisonthestopandjustabletocountertheeffectoftheengines.
Then,wecouldsaythatwehavereachedsomekindofminimumcontrolspeedasitisalimitofmanoeuvrability.
Onanymulti-engineaircraft,belowtheMinimumControlspeeds(VMC),thereisariskoflosingthecontroloftheplaneinthecaseoffailureofoneengine(outerforaquad)withtheother(s)atmaximumthrust.
ThereareseveralVMC:fortakeoffconfigu-rations,itiscalledVMCA(AforAirborne),forapproach,VMCL(LforLanding).
Onaquad,anotherone,VMCL-2,isassociatedwiththefailureof2enginesonthesameside,intheapproachconfiguration.
Ithastobedemonstratedforcerti-fication,althoughthislastsituationismainlyconsideredwhentakingoffforaferryflighton3engines,withoutpassengers,andifunfortu-natelyafailurehappensontheoth-erengineofthesameside.
Finally,thereisaVMCcoveringthecaseofthegroundaccelerationattakeoff.
ItiscalledVMCG(GforGround).
EverythingisnotblackandwhiteanditisnotbecausetheaircraftisflyingbelowaVMCthatcon-trolwillalwaysbelostorthatacrashwillinevitablyoccur.
Butwhatissureisthat,whenreach-ingtheVMC,thepilotisonalimitofmanoeuvrabilityandhecannotdowhathewantsfreelyinamanoeuvringsense.
SomerulesofdeterminationoftheVMCsareratherstrange,anditisdiffi-culttounderstandwhichlogicisbehindthat.
Neverthelesstheyhavebeenappliedforaverylongtimeandtheirvalidityhasbeenprovenbythelongexperienceonahugenumberofflighthoursonallaircrafttypes.
ForallVMCair-borne,thereisfirstastaticdemon-strationofthevalue,followedbydynamicteststoshowthatthema-noeuvrabilityremainssufficientatthisspeed.
VMCGisobtainedonlybyadynamicexercise.
Bynature,determinationsofVMCAandVMCLareriskyflighttests,asoneengineisshutdownatverylowaltitude.
Onatwin,thefailureofthe"live"enginegivesjustenoughtimetorelighttheotherone.
Onaquad,thesituationisdifferent,asintheeventofthelossoftheotherengineonthesamesideasthe"failed"one,thethrustontheremainingenginesmustbereducedimmediatelytoavoidalossofcontrol.
However,theriskoffailureofanotherengineduringthesetestshasaverylowprobability.
Thecriticalissueistheexecutionofthedynamictests,asitcanleadveryquicklytoalossofcontrol,duetotherapidbuildupofsideslip.
Suchaneventoccurredaverylongtimeagoinatestflight,butfortunatelycontrolwasimmediatelyrecoveredandthenmodificationsweremadetotheflightcontrolstoreducedras-ticallythisrisk.
Anyway,wehavetobeverycautiousintheexecu-tionofthesetestsandtheyareonlyperformedbywellexperiencedtestpilots.
MeasurementofVMCsisnotakeypriorityatthebeginningofthedevelopmentofalongrangeaircraft.
Thereasonisthatallthesespeedsareratherlowandthereforedonotaffecttakeoffandlandingperformances,exceptforoperationsatverylowweights.
Thisisnotpenalizingforanair-craftliketheA380.
However,itisalwaysusefultoperformsomemeasurementsatanearlystageoftheflightprogramtobesurethatwewillnothaveabadsurprise,whichmighthaveanimpactonperformancesathigherweightthanexpectedorcouldnecessitateamodificationofthedesignoftheflightcontrols.
FortheA380,wehadanissuetostartthesetestsas,duringthefirstmonthofflights,wediscoveredthattheverticalfinhadtobemodi-fied.
Duetothedelaynecessaryforthismodification,itwasdecidedtopostponeVMCsdeterminationbyseveralweeks,untilwereceivetheimprovedfin.
11Issue11|JANUARY2011TheAirbusSafetyMagazine1.
VMCA,VMCL,VMCL-2Whenenginesandsystemsareconfigured,westartabout20ktabovethepredictedvalue,then,wedecelerateslowlykeepinghead-ingconstant.
Necessaryrudderincreasesasthespeeddecreases,eventuallyuptothestop.
Furtherdecelerationwillneedsomebanktostillkeeptheheadingconstant.
The"true"VMCAisobtainedwhenthebankanglereaches5°intheoppositesensetothe"failed"engine(fig.
1).
Thisbankangleisveryimportantasitallowsafurtherspeedreductionofabout5to10kt,comparedtothesametestper-formedwithwingslevelled.
WhereisthisstrangerulecomingfromItisamystery!
Maybethat,intheoldtimes,whenreliableflighttestinstallationswherenotexisting,somebodyhadimaginedtohavesometoleranceonthebankangle,becauseitistruethataperfectsta-bilizationofthebankangleisdiffi-cultwhentherudderisonthestop.
Indoingso,heputsomeknots"inhispocket"!
Thenthetraditionhasbeenkeptandofficialised.
Thishy-pothesiscouldexplainthechoiceofthisodd5°value.
TheteststoobtainVMCLandVMCL-2aresimilar.
Butthereismoretodo.
Ademon-strationthattherollmanoeuvrabil-ityatVMCissufficientmustbeperformed.
TherulesareslightlydifferentforVMCAandVMCL5°bankangleFigure1VMCAdeterminationandherewewilljustshowoneex-amplefortheVMCL.
Atthisspeed,therollingcapacityisreducedonthesideofthedeflectionoftherud-der(attheoppositeofthe"failed"engine).
Theruleisthatitmustbepossibletogofrom5°bankangleonthesideoftherudderdeflection,upto25°inlessthan5seconds.
Whateverthetypeofaircraft,therearerisksinthistestasthesideslipisbuildingupveryquickly,be-causeitcannotbecompensatedbytheyawdamper,therudderbeingalreadyonthestop.
Whenpassing25°bank,therecoverymustbeim-mediateandverysmooth,withtheenginesreducedtoidle,thespeedincreasedandthesideslipcarefullyminimized.
AttheverybeginningoftheFlyByWireprograms,therewasplentyofrollcapabilityatlowspeed.
Butinordertoavoidreach-ingtoohighsideslip,therollratecommandedbythepilotwasdivid-edby2tobelimitedat7.
5deg/satlowspeedwhentheflightcontrolscomputersdetectalargeasymme-tryinthrust.
Thisrollrateallowsthistesttobepassedwithalmostnomargin.
Theavailablerolleffi-ciencytoreacttoturbulenceisnotmodified.
Therearesomeotherspecificdy-namictestsatVMCA,butthedem-onstrationisstraightforwardforouraircraft.
ThefirstVMCAandVMCLtestflightonA380wereperformedattheendofMay2006,unfortu-natelyinweatherconditionsnotidealforthesetypesofmeasure-ments.
Somedayslater,withbetterweather,asecondflightallowedustoconfirmtheresultsandalsotoperformVMCL-2tests.
Athirdandfinalflightwasdedicatedtocertifi-cation.
Usually,onotherprograms,allthesetestsareperformeddirect-lywiththeAuthoritiesonboard.
However,duetosomeparticu-laritiesoftheaircraft,thedecisionwasmadetoperformpreliminaryflightstobesurethattherewasnoissuewithwhatwasgoingtobepresentedforcertification.
TherewasnosurprisecomingfromtheseflightsandtheVMCA,VMCLandVMCL-2valueswerefoundtobeasexpected.
2.
VMCGTheVMCGisestablishedwithadynamictest.
Theaircraftisac-celeratedwithallenginesatmaxi-mumthrust,withthenosewheelsteeringdisconnectedtosimulateawetorcontaminatedrunway.
Atagivenspeed,theouterengineisshutdownwiththemasterlever.
Thepilotmusttrytominimizethelateralexcursion,usingtherudder(fig.
2).
AsfortheVMCA,athighspeedasmalldeflectionisneeded.
Butatlowspeed,evenwithfullrudder,therecouldbeasignifi-cantdeviation.
Bydefinition,theVMCGistheshutdownspeedforwhichthedeviationis30ft.
12Issue11|JANUARY2011Safety-30-101030Y(m)x(m)Figure2VMCGtestThistestmustbeperformedinper-fectweatherconditions,becauseevenaverylightcrosswindorsomesmallturbulencecanhaveanimpactontheresults.
Generallytheflighttestisplannedatsunrise.
Thefirsttestisusuallynotcritical,astheshutdownspeedisabout10ktabovetheplannedVMCG.
Thensomemoretrialsareperformedwithaprogressivereductionoftheshutdownspeed,bystepsof3,2oreven1kt,dependingontheresults.
Mostofthetime,afterabout6tests,the30ftdeviationisreached.
Infact,wetrytohaveatleastoneresultabove30fttobeabletoin-terpolatebacktotheVMCG,butwehavetobecarefulasaroundVMCG,thelateraldeviationisverysensitivetotheenginecut-offspeed.
Duringthisseriesoftests,thepilotinthelefthandseatisinchargeofthetrajectory.
Hetriestominimizethedeviationandthencompletesthetakeoffwhenthemaximumde-viationhasbeenreached.
Thepilotintherighthandseatshutsdowntheengineattheplannedvalue.
Itisimportanttohavealwaysthesamepilotdoingthesameactionas,ifthereisabiasintheshutdownspeed,itismostprobablygo-ingtobethesameforalltestsandthespeeddecreaseisgoingtobeasprogressiveasplanned.
Datare-ductionwillthenallowtheanalysisteamtodeterminetherightvalue.
Inthecockpit,onthejumpseat,atestflightengineermonitorstheenginesandisinchargeofthespe-cificrelightproceduresgenerallygivenbytheengineManufacturers,followingsuchshutdownsatmaxi-mumthrust.
AsfortheVMCA,mostofthetime,thesetestsaredirectlyusedforcertification,withanEASApilotinthelefthandseatandanAirbuspilotontheright.
Oneofthereasonsforminimisingthenumberoftimesthesetestsaredone,isthatrepeatingseveralshutdownsatmaximumthrustisdamagingforanengineandwetrytoreducethisrisk.
However,fortheA380,duetonumerousnewsystemsfea-turesandsomeuncertaintiesonthepredictions,wedecidedtoperformafirstevaluationourselves.
Theinitialresultsdemonstratedthatwewereright.
ThefirstVMCGflightcouldonlybeperformedaftertheinstalla-tionofthemodifiedfinandittookplaceonMarch30th2006.
Takeoffweightwas450tons,configuration3andthepredictedVMCGwas122kt.
Asusual,wedecidedtoper-formthefirsttestwiththeengineshutdownat132kt,10ktabovethepredictedvalue.
Itwasplannedto"fail"therightouterengine,thereforewelineduptheaircraft10metersontheleftofthecentreline.
Tohelp,wehaveononeoftheToulouserunways,fulllengthbluelinesat5and10metersoneachside.
Thismakesiteasierforthehandlingpilottokeeppreciselythedistancefromthecentrelineduringtheacceleration.
Therightenginewasshutdownat132ktasplanned.
Ataspeedabout10ktabovetheVMCG,thedeviationshouldnotexceed2meters,butwehadasur-priseastheaircraftstartedtoskidlaterallyandweeventuallyreachedRotationMaximumlateraldeviationreachedFullleftrudderpedalinputEngine#4shutdownBrakerelease13Issue11|JANUARY2011TheAirbusSafetyMagazineadeviationof15metersandwewentontheothersideofthecen-treline.
Agooddemonstrationthatitwasasoundideatotakesomeprecautionsandlineup10metersontheleft,asifwewerealreadyattheVMCG!
AnextrapolationletusthinkthattheVMCGwasprobablyatleast13ktabovetheestimatedvalue,whichwouldhavehadseri-ousadverseconsequencesforair-craftperformance.
Welandedimmediatelyanddecid-edtoredothetestataslightlyhigh-erspeed:134kt.
Anewsurprise:thedeviationwasalmostthesame,justabitsmaller.
Thevideoswereshowingthetyresofthemainland-inggearsskiddingontherunway.
Athirdtestwasperformedat136kt.
Thedeviationwas18meters.
Itwasincreasingwiththespeed!
Clearly,somethingwasabnormal.
Thefollowingday,inordertoun-derstandthereasonsofthisstrangebehaviour,wetriedagain,butthistimewithaconfiguration1+Fin-steadof3.
Withalowerflapsset-ting,wewereexpectinghigherforcesonthelandinggears,whichshouldhaveimprovedfrictionandthereforereduceskidding.
Weshutdowntheengineat135ktandthedeviationreached18meters.
Basi-cally,nochange!
Ontop,wedis-coveredananomaly:becauseofahiddenfailure,thedeflectionofoneofthe2rudderswastooslow.
Onlyoneservocontrolofthisrud-derwasactive,insteadof2inthistypeofsituation.
Thiswasnotthemainreasonforthehugedeviation,butthesystemwasnotrobust.
AbatchofmodificationswasneededbeforecontinuingVMCGtests.
Toimprovethesituation,itwasnecessarytoenhancetheefficiencyoftheflightcontrolsinyawafteranenginefailure.
Therefore,inordertocreatesomeadditionalyaw,thesolutionwastoincreasethedragonthewingwhichisonthesideofthedeflectedrudderswhentheyareclosetotheirstop.
Forthat,onespoilerand2ofthe3aileronswerefullydeflectedintheupperdirec-tionwhilethecentreaileronwasputdown(fig.
3).
Havingaileronsindifferentdirectionspermittedtominimizetheeffectonthebankan-gle.
Somemodificationswerealsomadeinthecomputers,allowingfasterdeflectionofruddersinthisspecificsituation.
Duetoweatherconditions,weperformedthetestswithallthesemodificationsatIstresAirBaseonJune14thwithexcellentresults:theVMCGwasnowasplanned,around122kt.
Howevertheexactvaluewasfinallydetermineddur-ingthecertificationflightatthebe-ginningofSeptember.
ThereasonisthatthevalueoftheVMCGisverysensitivetothepilotreactiontime.
Thisoneisaround0.
6sec-onds,but0.
1secondmoreorlesscanmodifytheVMCGby1or2kt.
TheofficialvalueisgivenbythetestsperformedbythecertificationpilotfromEASA.
ThefinalvalueagreedafterdatareductionfortheRuddersclosetostopSpoilerandaileronsdeflectionFigure3VMCG–enhancedyawcontrolongroundRollsRoyceenginesis119or121kt,dependinguponthemaximumenginethrust(optionchosenbytheCustomers),whichisslightlylessthantheplannedfigures.
14Issue11|JANUARY2011SafetyMarcBAILLIONFlightSafetyDirectorLorraineDEBAUDUSGroupManagerA318/A319/A320/A321OperationalStandards,CustomerServicesRadioAltimetererroneousvalues2.
SystemarchitectureAllAirbusaircraft,excepttheA380,areequippedwithtwoRAs,whichprovideheightinformationtoseveralaircraftsystems(fig.
1).
TheA380isfittedwiththreeRAs,whichprovidetheaircraft'ssys-temswithasinglemedianheightvalue.
Asaresultofthissystemar-chitecture,asingleerroneousRAheightindicationisnotanissuefortheA380.
Thisarticlewillthereforecon-centrateontheothermembersofAirbus'familyofaircraft,fittedwithtwoRadioAltimeters.
ThesetwoRAsprovideheightin-formationtotheAutoPilots(AP),AutoThrust(A/THR),Primary1.
IntroductionIn-serviceeventsoccurredwhereaRadioAltimeter(RA)providedaner-roneousheightindication,whichwasrecognizedasvalidinformationbytheaircraftsystems.
Thisresultedinanear-lyflareactivationduringtheapproach.
Inresponsetotheseevents,Airbuslaunchedaseriesofinvestigationthatledtothefollowingconclusions:inthemostcriticalscenario,anearlyactivationoftheflarelawmayleadtoanincreaseoftheAngleofAttackwhich,ifnotcorrected,couldreachthestallvalue.
AllAirbusaircraftareaffectedexcepttheA380.
Asaresultoftheseinvestigations,Airbuspublished:qAsetofOperatorInformationTelex/FlightOperationsTelex(OIT/FOT)andRedOperationsEngineeringBulletins(OEB)describingtheopera-tionalconsequences,andcontainingrecommendationstofollow,shouldaRAprovideerroneousheightreadings.
qNewtasksintheTroubleShootingManual(TSM)andMaintenancePlan-ningDocument(MPD)relatedtotheRAantennasandcoaxialcables.
ErroneousRAoccurrencesshouldbesystematicallyreportedsoastoallowproperimplementationoftherecom-mendedmaintenancetasks.
Thesecon-sistintheinspectionoftheRAantennascoaxialcables,cleaningoftheantennasandpossiblyreplacementoftheRA.
DesignimprovementsarecurrentlyunderdevelopmentontheRadioAltimeteraswellasonotheraircraftsystems,inordertobetterdetectRAerrorsandtoavoiduntimelyflareengagement.
Figure1RA1andRA2receiver(R)andtransmitter(T)antennaslocationonanA320FlightDisplays(PFD)/NavigationDisplays(ND),WeatherRadar(WXR),FlightWarningComput-ers(FWC),TrafficAlertandCol-lisionAvoidanceSystem(TCAS)andallaudioindicators.
HeightinformationisreceivedfromoneRAatatime.
Incaseofdetectedfailure,theremainingRAisusedasaback-up.
Thefollowingsystemsarede-signedtoreceiveanRAsignalfromonlyasinglesource:qOnallaircraftmodelstheTerrainAwarenessandWarningSystem(TAWS)receivessignalsfromRA1only.
qOntheA300B2/B4,A300-600andA310,theAutoPilot/FlightDirectoruseonlytheiron-sideRA.
15Issue11|JANUARY2011TheAirbusSafetyMagazine3.
TypicalcauseoferroneousRAheightindicationsIn-serviceexperiencehasshownthataRadioAltimetermayprovideerroneousheightindicationsduetoadirectlinkbetweenthetrans-mitterandthereceiverantennas,withoutgroundreflection.
ThiscanberelatedtocausesthatareeitherinternalorexternaltotheRAsystem.
Theinternalcausesmaybelinkedto:qWaterflowontheantennas,e.
g.
duetoadefectivedrainvalve.
qWateringressintotheRAantennainstallationaffectingtheantennas,andpotentiallythecoaxialcables.
qCarbondirtoriceaccretionontheantennas.
qDegradedinstallationatconnec-torslevel.
Theexternalcausesmaybelinkedtoaircraftflyingover:qOtheraircraft,hailcloudsorbrightspots,i.
e.
terrainpresentingreflectivityvariations.
qRunwayscontaminatedwithwa-terorsnow.
Inthesecases,theRAconditionmaynotbedetectedbythesystems,whichcontinuetousetheerroneousRAvalues.
Avalueof-6fthasbeenobservedinanumberofevents.
4.
OperationalconsequencesandrecommendationsAnerroneousRAheightindicationmayhaveeffectsonthe:qPrimaryFlightDisplays(PFD)qSystemsDisplays(SD)qWarningsandcalloutsqAutoFlightSystemmodechangesqAircraftprotections,suchastheunavailabilityoftheHighAngleofAttackAutoPilotdisconnection.
ThetwofollowingexamplesillustratepossibleeffectsofanerroneousRAindicationonanA320Family/A330/A340aircraft:a)IndicationlowerthanrealheightonRA1duringanILSapproach,withbothAPs/FDsengaged:qFigure2showsthecrew'sPFDsbeforetheRA1issue.
BothRAsfunctionproperlyandprovidethesameheightof1960ft.
Theverti-calmodeisonG/S,andthelateralmodeisonLOC.
TheA/THRisengagedinSPEED.
qFigure3RA1providesanerroneousheightindicationof–6ft,whileRA2deliversthecorrectheightof1400ft.
Consequencesontheaircraft'ssystems:qRA1providesheightinforma-tiontoPFD1,AP1andtotheA/THR(theA/THRusesthesameRAasthemasterAP).
Therefore:TheRAreadingonPFD1is–6ftAP1engagesinFLAREmodeandPFD1displays"FLARE"ontheFMATheA/THRengagesinRE-TARDmodeanddisplays"THRIDLE"ontheFMAofPFD1andPFD2.
Figure2BothRAsprovidecorrectheightof1960ft1960CaptainF/OIdenticaltoCaptainsideAP1+2EngagedFigure3ErroneousRA1readingis–6ft,correctRA2readingis1400ft.
BothAP/FDsareengaged1400CaptainF/OAP1+2EngagedErroneousRA16Issue11|JANUARY2011SafetyqRA2providesheightinforma-tiontoPFD2andtoAP2.
Therefore:TheRAreadingonPFD2is1400ftAP2isstillengagedinG/SverticalmodeandLOClateralmode.
PFD2thereforedisplays"G/S"and"LOC"ontheFMA.
qAP1isengagedinFLAREmodeandoneRAheightgoesbelow200feet.
Inaddition,thedifferencebetweenbothRAheightindica-tionsisgreaterthan15feet.
Therefore:TheAUTOLANDwarninglightsareactivated.
Figure4BothRAsprovidecorrectheightof1960ftFigure5ErroneousRA1readingis–6ft,correctRA2readingis1400ft.
AP1andbothFDsareengagedb)IndicationlowerthanrealheightonRA1duringanILSapproach,withAP1andbothFDsengaged:qFigure4showsthecrew'sPFDsbeforetheRA1issue.
BothRAsfunctionproperlyandprovidethesameheightof1960ft.
Theverti-calmodeisonG/S,andthelateralmodeisonLOC.
TheA/THRisengagedinSPEED.
qFigure5showsthatRA1pro-videsanerroneousheightindica-tionof–6ft,whileRA2deliversthecorrectheightof1400ft.
Consequencesontheaircraft'ssystems:qRA1providesheightinforma-tiontoPFD1,AP1andtotheA/THR(theA/THRusesthesameRAasthemasterAP).
Therefore:TheRAreadingonPFD1is–6ftAP1engagesinFLAREmodeanddisplays"FLARE"ontheFMAsofPFD1andPFD2.
TheA/THRengagesinRETARDmodeanddisplays"THRIDLE"ontheFMAsofPFD1andPFD2.
qRA2providesheightinforma-tiontoPFD2.
Therefore:TheRAreadingonPFD2is1400ft.
qAP1isengagedinFLAREmodeandoneRAheightgoesbelow200feet.
Inaddition,thedifferencebetweenbothRAheightindica-tionsisgreaterthan15feet.
Therefore:TheAUTOLANDwarninglightsareactivated.
1960CaptainF/OIdenticaltoCaptainsideAP1Engaged1400CaptainF/OAP1EngagedErroneousRA17Issue11|JANUARY2011TheAirbusSafetyMagazineIntheexamplesabove,theriskofearlyflareengagementduetothetoolowheightindicationiscom-poundedbythepossibleimpactontheaircraftprotections.
OntheA320Family,forexample,theCONFFULLHighAngleofAt-tackAutoPilotdisconnectionisnotavailableintheeventofaverylowerroneousRAheightindication.
Therefore,ifamanualtakeoverisnotperformedwhenthisearlyflareengagementoccurs,theAngleOfAttackwillincreaseandmayreachthestallvalue.
Thedetailedeffectsonaircraftpro-tectionontheA300/A310,A320andA330/A340familiescanbefoundintheOIT/FOTandOEBreferencedattheendofthisarti-cle.
Thesedocumentsincludeaswellthefollowingoperationalrec-ommendationsintheeventofanerroneousRAheightreading:qDuringallphasesofflight,theflightcrewmustmonitorandcrosscheckallprimaryflightparametersandFMAindications.
qDuringILS(orMLS,GLS)ap-proachwithAPengaged,intheeventofanunexpectedTHRIDLEandFLAREmodesengagement,theflightcrewmustimmediatelyreactasfollows:ImmediatelyperformanautomaticGoAround(thrustleverssetinTOGA),OrImmediatelydisconnecttheAP,thencontinuetheland-ingusingrawdataorvisualreferences(FDssettoOFF)or,performamanualGoAroundwiththrustleverssettoTOGA(significantlongitudinalsides-tickinputmayberequired).
SeeOEBfordetailedproceduresReferences:OIT/FOTSE999.
0034/09dated4thMay2009forA320/A330/A340operatorsqA318/A319/A320/A321:REDOEB201/2qA330:REDOEB076/2qA340:REDOEB091/2OIT/FOTSE999.
0035/09dated30thApril2009forA300/A310operators(noREDOEBastheoperationalconsequencesaredifferentthanfortheA320/A330/A340).
TheOIT/FOTsandOEBsarenotapplicabletotheA380.
TheFlightcrewsmustreportanyoftheabovesymptomsintheaircrafttechnicallogbook,inordertoensurenodispatchwithanerroneousRA.
SeveralsymptomsmayassistthecrewinidentifyingapotentialerroneousRAreading:qUntimelyECAML/GNOTDOWNwarningsqUntimelyorno"RETARD"calloutqInterruptionof,ornoRAauto-maticcalloutqUntimelyTAWSalert("PULLUP"or"TERRAINAHEAD")qImpossibleNAVmodeengage-mentaftertakeoffqPulsingCabinDifferentialPressureAdvisoryonECAMCABPRESSpage.
Inadditiontotheabovecockpitindications,RAfaultmessagesfromtheElectricalFlightControlSystem(EFCS)mayalsoberecordedinthePostFlightRecord.
6.
DesignImprovementsThefollowingimprovementsarebeingimplementedintheRAsys-temaswellasintheaircraftsystemswhichusetheRAinformation:qRAsystem:Anewgelgasket,betweentheantennaandtheaircraftstructure,willprovidebetterisolationagainstwateringress.
AdigitalRA,withselfmoni-toringcapabilitytoeliminatetheerroneousheights,isundercertification.
qAircraftsystems:BoththeAutoPilotandflightcontrolsystemswillbeenhancedtodetectmostRAerroneousheightvalues.
7.
ConclusionTheaircraftsystemsmaynotalwaysdetectanerroneousRadioAltimetervalue.
DependingontheflightphaseandAP/FDandA/THRstatus,promptactionfromthecrewmayberequiredtopreventtheconsequencesofsuchsituation.
ItisessentialthatthecrewidentifiesthesymptomsofanerroneousRAreadingsoasto:qTakeimmediateactions.
qReportthesesymptomstohelpmaintenanceteamstroubleshooter-roneousRAreadings.
5.
MaintenancerecommendationsIftheflightcrewsreportsymptomsofanerroneousRAheightindica-tion,thefollowingmaintenanceactionsshouldbeperformed:qCleantheRAantennasandtheadjacentareawithcleaningagents(MaterialN°11.
010)andalintfreeclothqIf,duringanysubsequentflight,thesymptomspersist:ReplacetheRAantennasInspecttheRAantennascoaxialcables.
Iftheyarenotincorrectconditions,repairorreplacethem.
TheserecommendationshavebeenaddedinthefollowingnewTSMtasks:q34-42-00-810-844(A320Family)q34-42-00-810-862(A330/A340)q34-42-00-006-00(A300/A310).
Inaddition,scheduledmaintenance(MPD)includenewtasksrelatedtotheRA:Every6months:RAantennasurfacecleaningEvery12years:replacementofRAantennasandRAcoaxialca-blesduringtheheavymaintenancevisitforthestructuresection.
18Issue11|JANUARY2011SafetyStéphaneGRANGERA320FamilyAutoflightSystemManagerDesignOfficeEricJEANPIERRESystemManagerA320FamilyProgramAutomaticNAVengagementatGoAround2.
Operationalcontext2.
1.
GoAroundoptionsThecrewmustalwaysbepreparedforaGoAround,eventhoughitisaninfrequentoccurrence.
AftertheinitiationofaGoAround,therearetwooptions:qInthemostprobableone,thecrewfollowsthepublishedMissedApproachprocedure.
qOtherwise,ifclearedbyATC,thecrewfollowsaconstantheading.
Theheadingtargetcanbepresetbythecrewduringtheapproach.
1.
IntroductionWhateverthereasonstoperformaGoAround,theneedhasarisenforanautomaticengagementofNavigation(NAV)mode.
Tomeetthisincreasinginterest,anoperationalenhancementcalled"NAVinGoAround"hasbeendevelopedbyAirbus.
Thisarticlepresentstheopera-tionalcontext,andthesolutionproposedwithitsadvantages.
2.
1.
CurrentGoAroundprocedureTheGoAroundissystematicallyinitiatedbypushingthethrustleverstoTOGA.
ThisensurestheengagementoftheGoAroundTrack(GATRK)AutoPilotand/orFlightDirectorlateralmode1.
TheFMSenteredpublishedMissedApproachprocedurebecomespartoftheACTIVEF-PLNandthepre-viouslyflownapproachisstrungbackintotheF-PLNattheendoftheMissedApproachprocedure.
TheGATRKmodeguidestheair-craftonaconstanttrack(whichisthecurrenttrackwhentheGoAroundisinitiatedwithwingslevel).
OncetheGoAroundisinitiated,thecrewwilllikelyflythepublishedMissedApproachprocedure:thePilotFlying(PF)orthePilotNonFlying(PNF)willhavetoengagetheNAVmodebypushingtheHDG/TRKselectorontheFlightControlUnit(FCU).
Therefore,inthemostprobableGoAroundscenario,thecrewwillper-formtwomainactions(asfarastheAutoflightsystemisconcerned):qPushthethrustleverstoTOGAqPushtheHDG/TRKselector.
2.
2.
ObjectivesofthemodificationThemodificationreducesthecrewworkload,andlimitsthepotentialdeviationsfromtherequiredflightpathwhenperformingaGoAround.
ItcoversthemostprobableGoAroundscenario,wherethecrewhastofollowthepublishedMissedApproachprocedure.
Moreover,itmakestheGoAroundprocedureassimilaraspossibletotheTakeOffprocedure.
Finally,inthecontextofRNP-ARoperationswheretheaircraftismorelikelytobeinaturn,itwillnotinter-rupttheturnincaseofaGoAround.
1:AswellastheSpeedReferenceSystem(SRS)AutoPilotand/orFlightDirectorlongitudinalmode,iftheaircraftisnotinacleanconfiguration.
19Issue11|JANUARY2011TheAirbusSafetyMagazine3.
PrincipleofthemodificationTheprincipleistokeeptheNAVmodeengagedor,ifavalidflightplanexists,toarmtheNAVmodeattheinitiationoftheGoAround.
ThepilotdoesnotneedtopushtheFCUselectoranymore:thenewlogicsdoitautomatically.
TheAutoFlightSystemautomati-callyfollowsthepublishedMissedApproachprocedure.
TheAP/FDmodesengagedareiden-ticaltothemodesthatwouldhavebeenengagedbypushingontheFCU"HGD-TRK"selectorimmediatelyaftertheGoAround:Without"NAVinGoAround"modificationTOGAthrustisappliedandtheSRS/GATRKmodesareengaged.
ThecrewhastoarmtheNAVmodemanuallybypushingontheFCUHDG/TRKknob.
Then,theFMAdisplaystheNAVmode.
With"NAVinGOAround"modificationWhenTOGAthrustisapplied,theSRS/GATRKmodesareengaged.
Inaddition,theNAVmodeisautomaticallyarmedwithoutanycrewactionontheFCU.
TheNAVmodeengagesimmediately(orassoonastheaircraftpassesabove100ftiftheGoAroundhasbeeninitiatedbelow100ft).
TheaircraftisguidedalongtheMissedApproachprocedure.
qInanon-precisionapproachwithmanagedlateralguidance(NAV,APPNAVorFINALAPP),theNAVmodeiskeptengaged.
qInanon-precisionapproachwithselectedlateralguidance(HDGorTRK),theHDGorTRKmodeiskeptengagedandtheNAVmodeisautomaticallyarmed(ifavalidflightplanexists).
qInaprecisionapproach(ILS,MLSorGLS)orinaFLS/MixedLOC-VNAVapproach,theGATRKmodeisinitiallyengaged(ascurrently)andtheNAVmodeisautomaticallyarmed(ifavalidflightplanexistsandifnoheadingpresethasbeenselectedduringtheapproach).
Inotherwords,theAP/FDmodeengage-mentsequenceisstrictlythesameaswhenthepilotpushesthethrustleverstoTOGAandpushestheHDG/TRKFCUselector.
The"NAVinGoAround"modificationdoesnotmodifytheaircraftbehaviouronthelongitudinalaxis.
4.
TypicaloperationalscenariosGoAroundsduringPrecisionAp-proachesaretypicallyperformedwhenvisibilityconditionsarenotmetattheDecisionAltitude/Height(DA/DH).
TheStandardOperatingProceduresspecifythataGoAroundisperformedbysettingboththrustleverstoTOGA.
Thefollowingtableillustratesthereductioninworkloadintroducedbythe"NAVinGoAround"modification.
20Issue11|JANUARY2011SafetyThe"NAVinGoAround"modificationdoesnotchangeoperationalproceduresinthefollowingscenarios:qGoAroundinHeadingmodewithaheadingpresetWhenclearedbyATCtofollowaconstantheadingincaseofMissedApproach,thecrewmaypresettheheadingontheFCU.
IfaGoAroundisinitiated,theNAVmodeisnotautomaticallyarmed(prior-ityisgiventothepreset).
ThecrewwillthenjusthavetopulltheFCUHDG/TRKknobtoengagetheHeadingmode.
qGoAroundinHeadingmodewithoutheadingpresetIncaseofalateclearancefromATCtofollowaconstantheadingaftertheGoAround(noheadingpreset),thecrewwillhavetoturntheFCUHDG/TRKknobtose-lecttheheadingtargetthenpulltoengagetheHeadingmode.
Inthiscase,theNAVmodeisautomati-callyarmedthenengagedatGoArounduntilthepullactionontheFCU.
5.
CONCLUSIONWiththe"NAVinGoAround"modification,theNAVmodeisau-tomaticallyarmedattheinitiationoftheGoAround2.
Themodewillthenengageassoonasthecaptureconditionsaremet.
Thismodificationreducesthecrewworkload,andlimitsthepoten-tialdeviationsfromtherequiredflightpath,whenperformingaGoAround.
ThenewlogicsareconsistentwiththemostprobableMissedAp-proachscenarioandareessentialforspecificoperationssuchaslowRNP.
ImpactonaircraftandassociatedMODandSBFortheA320Family,A330/A340andA380,theactivationofthefunctionrequiresthefollowing:qThehardwarepinprogrammingofeachFMG(E)CorsoftwarepinprogrammingofeachPRIMcomputers,andifrequired,theupgradeoftheflightguidanceorPRIMsoftware.
qTheupdateofvolumes:1.
22.
30,3.
03.
2,4.
05.
80.
oftheFlightCrewOperatingManual(FCOM).
A320FamilyThe"NAVinGoAround"modificationwillbecometheproductionstandardstartingfrom:A318:MSN4169A319:MSN4522A320:MSN4674A321:MSN4560ItwillalsobeincludedinthelowRNPmodificationpackages(MOD38073LowRNPstep2+,MOD150371/150372/150373LowRNPstep3andMOD151180RNP0.
3AR).
A330/A340The"NAVinGoAround"modificationwillbecometheproductionstandard,MSNtobeconfirmed.
ItwillalsobeincludedinthelowRNPmodificationpackages(MOD200192LowRNPstep2forFMSR1AThalesontheA330andnewMODSRNPstep2forFMSR1AHoneywellontheA330andA340-500/600).
A380The"NAVinGoAround"modificationwillbecometheproductionstan-dard,MSNtobeconfirmed.
2:Ifnoheadingpreset.
AircrafttypeMODNumberSBreferenceFMG(E)CorPRIMminimumstandardsA320Family3839922-1296P1I11(MOD37311)orS4I11(MOD37252)forA320IAE/PWFamilyP1C12(MOD37934)orS4C12(MOD37935)forA320CFMFamilyA330/A340200383PendingFMGECcertifica-tionP4HJ1(MOD57545)orT4HJ1(MOD57547)forA330PW/RRP4G1(for57544)orT4G1(MOD57548)forA330GEP4F1(MOD57546)orT4F1(MOD57549)forA340-200/300P4K2orT4K2(MODToBeDefined)forA340-600A380Underdevelopment21Issue11|JANUARY2011TheAirbusSafetyMagazineIssue10,August2010–A380:Fluttertests–OperationalLandingDistances:Anewstandardforin-flightlandingdistanceassessment–GoAroundhandling–A320:Landinggeardownlock–SituationawarenessanddecisionmakingIssue9,February2010–A320Family:Evolutionofgroundspoilerlogic–Incorrectpitchtrimsettingattakeoff–TechnicalFlightFamiliarization–OxygensafetyIssue8,July2009–TheRunwayOverrunPreventionSystem–TheTakeOffSecuringfunction–Computermixability:Animportantfunction–FuelspillsduringrefuelingoperationsIssue7,February2009–AirbusAP/FDTCASmode:Anewsteptowardssafetyimprovement–Brakingsystemcrossconnections–UpsetRecoveryTrainingAid,Revision2–FuelpumpsleftinOFFposition–A320:AvoidingdualbleedlossIssue6,July2008–A320:Runwayoverrun–FCTLcheckafterEFCSresetonground–A320:PossibleconsequenceofVMO/MMOexceedance–A320:Preventionoftailstrikes–Lowfuelsituationawareness–Rudderpedaljam–WhydocertainAMMtasksrequireequipmentresets–Slide/raftimprovement–CabinattendantfallingthroughtheavionicsbayaccesspanelincockpitIssue5,December2007–NewCFITeventduringNonPrecisionApproach–A320:Tailstrikeattakeoff–Unreliablespeed–Compliancetooperationalprocedures–ThefutureairnavigationsystemFANSBIssue4,June2007–OperationsEngineeringBulletinreminderfunction–AvoidinghighspeedrejectedtakeoffsduetoEGTlimitexceedance–DoyouknowyourATC/TCASpanel–Managinghailstorms–IntroducingtheMaintenanceBriefingNotes–A320:Dualhydraulicloss–TerrainAwarenessandWarningSystemsoperationsbasedonGPSdataIssue3,December2006–Dualsidestickinputs–Trimmablehorizontalstabilizerdamage–Pitotprobesobstructiononground–A340:Thrustreverserunlocked–Residualcabinpressure–CabinOperationsBriefingNotes–Hypoxia:AninvisibleenemyIssue2,September2005–Tailpipeorenginefire–Managingsevereturbulence–AirbusPilotTransition(ATP)–RunwayexcursionsattakeoffIssue1,January2005–GoAroundsinAddis-AbabaduetoVORreceptionproblems–Theimportanceofthepre-flightflightcontrolcheck–A320:In-flightthrustreverserdeployment–AirbusFlightSafetyManagerHandbook–FlightOperationsBriefingNotesArticlespublishedinpreviousSafetyFirstissues22Issue11|JANUARY2011SafetySubscriptionFormSafetyTheAirbusSafetyMagazineSubscriptionFormTobesentbacktoAIRBUSFLIGHTSAFETYOFFICEFax:33(0)561934429Mailto:marie-josee.
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comNameSurnameJobtitle/FunctionCompany/OrganizationAddressPost/ZipCodeCountryTelephoneCellphoneFaxE-mail(Mandatoryforbothdigitalandpapercopies)Pleasesendmethedigitalcopy*PPleasesendmethepapercopy*P(Pleasenotethatpapercopieswillonlybeforwardedtoprofessionaladdresses)*PleaseticktheappropriatecaseSafety