Landinggearfailureduringlandingrunat
OuluAirporton3October2016
Investigationnumber:L2016-02
SYNOPSIS
Based on section 2 of the Safety Investigation Act (525/2011), the Safety Investigation Authority,Finland(SIAF)decidedtoinvestigateanaccidentthatoccurredtoaReimsF406CaravanIIaircraft,registeredOH-OTL,atOuluAirporton3October2016.Therightmainlanding
gear of the aircraft collapsed during landing run. Major (ret.) Pekka Alaraudanjoki was appointed as team leader for the investigation group, and B. Eng Jan Nordlund as an expert
memberofthegroup.ChiefInvestigatorIsmoAaltonenactedasinvestigator-in-charge.
TheaccidentwasreportedtotheEuropeanAviationSafetyAgency(EASA),toTheBureauof
InvestigationandAnalysisforCivilAviationSafety(BEA)ofFranceandtotheNationalTransportationSafetyBoard(NTSB)oftheUnitedStates.BEAandNTSBdesignatedanaccredited
representativetotheinvestigation.
Theinvestigationreportdescribestheeventsbeforetheaccidentandafterit.Italsoreviews
therescueoperationsandanalysesthefactorscontributingtotheaccident.Finally,safetyrecommendationsareissuedtopreventsimilaraccidentsinthefutureortomitigatetheirconsequences.
Thepurposeofasafetyinvestigationistoenhancesafetyingeneral,topreventaccidentsand
incidents,andtocounteractanydamagecausedbyaccidents.Theinvestigationdoesnotaddressany questionsofresponsibilityorliabilityfordamages.Useoftheinvestigationreport
forreasonsotherthanimprovementofsafetyshouldbeavoided.
The investigation was initiated at OuluAirportbyphotographingthedamagetotheaircraft
and the marks on the runway. A SIAF investigator was present when the collapsed landing
gearwasremovedfromtheaircraftinOuluandre-installedtemporarilyformovingtheaircraft.Sincethecauseoftheaccidentwasrevealedduringlandinggearremoval,thetechnical
staffofLapinTilauslentoOywerepermittedtoexamineotherdamagecausedtotheaircraft
intheaccidentinmoredetail.Theylatergaveareportonthedamagetotheinvestigators.The
investigationgroup visitedLapinTilauslentoOy’srepair stationatRovaniemiAirporttoreview the company operations and to check their instructions and arrangements related to
maintenance.Finaviawasrequestedtoprovideanaccountoftheactionstakenbyairtraffic
controlandrescueservicesatOuluAirportinconsequencetotheincident.
Anopportunitywasreservedforthoseinvolvedintheaccidentandtotheauthoritiesresponsibleforsupervisioninthefieldoftheaccidenttocommentonthedraftinvestigationreport.
The comments were taken into account when finishing the report. A summary of the commentsreceivedis availableonthelastpagesofthisreport.However,nocommentsgivenby
privateindividualshavebeenpublished.
TheinvestigationreportwastranslatedintoEnglishbyLeilaIikkanen.Thereport,including
itssummaryandappendices,hasbeenpublishedontheSIAFwebsiteatwww.sia.fi.
Investigationnumber:L2016-02
Investigationreport6/2017
ISBN:978-951-836-488-0(PDF)
Coverphoto:Finavia,OuluAirport
2
TABLEOFCONTENTS
SYNOPSIS................................................................................................................................................................................2
1
FACTUALINFORMATION......................................................................................................................................4
1.1
Historyoftheflight.........................................................................................................................................4
1.2
Damagetoaircraft...........................................................................................................................................5
1.3
Personnelinformation..................................................................................................................................5
1.3.1
Pilots.............................................................................................................................................................5
1.3.2
Technicalpersonnel..............................................................................................................................5
1.4
Aircraftinformation........................................................................................................................................6
1.4.1
2
1.5
Meteorologicalinformation........................................................................................................................7
1.6
Aerodromeinformation................................................................................................................................7
1.7
Investigationoftheaccidentsiteandaircraft....................................................................................7
1.8
Medicalinformation.......................................................................................................................................8
1.9
Rescueactionandsurvivalaspects.........................................................................................................8
1.10
Detailedinvestigations.............................................................................................................................8
1.11
Organisationalandmanagementinformation...........................................................................12
1.12
Otherinformation....................................................................................................................................13
ANALYSIS...................................................................................................................................................................14
2.1
3
4
Descriptionofthelandinggearsystem.......................................................................................6
Accidentanalysis...........................................................................................................................................14
2.1.1
Probleminlandinggearretraction.............................................................................................14
2.1.2
Actionsandtrouble-shootinginflight.......................................................................................14
2.1.3
Landinggearfailure............................................................................................................................15
2.1.4
Rescueaction.........................................................................................................................................16
CONCLUSIONS.........................................................................................................................................................17
3.1
Findings.............................................................................................................................................................17
3.2
Probablecauses.............................................................................................................................................18
SAFETYRECOMMENDATIONS........................................................................................................................19
4.1
Safetyactionsalreadyimplemented...................................................................................................19
4.2
Safetyrecommendations...........................................................................................................................19
4.2.1
ReviewofmaintenanceinstructionsforReimsF406CaravanIIaircraft................19
4.2.2
ReviewofmaintenanceinstructionsforotherCessnamodels.....................................19
REFERENCEMATERIAL...............................................................................................................................................21
SUMMARYOFTHECOMMENTSRECEIVEDONTHEDRAFTINVESTIGATIONREPORT.............22
Appendix1. Accimapgraph
3
1 FACTUALINFORMATION
1.1 Historyoftheflight
AReimsF406CaravanIIaircraft(OH-OTL),operatedbytheFinnishcompanyLapinTilauslentoOy,departedforaroutinecargoflightfromRovaniemiAirporttoOuluon3October2016.
Theaircrafthadatwo-pilotcrewandcarried347kgofmail.Therewerenootherpersonson
boardbesidesthecrew.
Flightpreparation,aircraftloadingandtaxiingfromthestandtotake-offpositionwereuneventful.Taxiingdistancewasabout800m.Theaircrafttookoffonrunway03at19:30–all
times in thisreport are Finnishlocal time.Theweatherwasgoodanditwasstartingto becomedarkatthattimeintheevening.Whenthelandinggearwasretracted,theGEARUNLOCKED
warninglightandthe HYDPRESSONindicatorforthehydraulicsystemremainedon.Atthepilot-in-command’s request, the co-pilot selected gear back down, and the three green lights
indicatingthatthegearwasdownandlockedilluminatednormally.TheHYDPRESSONindicator
andGEARUNLOCKEDwarningwerealsoextinguishedasusual.
Thepilot-in-commandcontinuedflyingtowardsOulu,andtheco-pilotsearchedtheemergencychecklistsfor suitable procedures forthesituation.Anyproceduresdirectlyapplicable to
this malfunction were not found, but the pilots decided to follow the procedure for cases
wheretheHYDPRESSONlightremainedoncontinuously.Theprocedureassistedinisolatingthe
fault to the landinggear system, but the exact nature ofthe malfunction was not clear. The
pilotstooktheactionsasinstructed,exceptthatthepoint”landinggearswitch-rapidlyrecycle”wasomitted,sincethegearwasalreadyextendedandtheindicatorlightsshowedthatit
wasdownandlocked.
Thepilot-in-commanddecidedtocontinuetoOuluwiththegeardown,astheproceduredid
notcall forlanding assoonaspossibleandtheweatherwasgood.Approachandlanding at
Ouluwereperformedindarknessat20:05.Theaircrafttoucheddownatthebeginningofthe
runway,andthelandingrunwasnormalatfirst.Whentheplanehaddeceleratedtoaspeedof
about60kt1,thepilot-in-commandstartedbraking,atwhichtimetherightmainlandinggear
collapsed and the aircraft tilted to theright. The pilot-in-command stated thathe had managedtokeeptheplaneontherunwayusingnosewheelsteering,brakinghardontheleftside
andapplying reverse thrustinthe leftengine.Theaircraftstoppedquicklyafterthelanding
gearhadcollapsed,withinadistanceofabout80m.
Theaircraftcametoastopontherightedgeofrunway30,remainingwellonthepavedsurface.Theengineswererunninguntiltheplanestoppedandwerethenshutdown.Thepilotin-command asked the co-pilottoreporttheincidenttotheATCandrequestatowvehicle.
Aftersending the report, electricalpowerwasswitchedoff.ATCalertedtherescueservices,
andthepilotsexitedtheplaneuninjured.
Rescue services moved the aircraft off the runway using pneumatic lifting pads and a
transportplatform.
Therunwaywasclosedforaboutthreehours,until23:00.ANOTAM2wasissuedat20:42to
notifyotheraircraftofthis.Oneairlinerturnedbacktoitsdepartureairport,Helsinki,andat
1Knots(kt)=1.852km/h,60knotsequalsabout111km/h
2NOticesToAirMen,aninformationnoticetoaviators
4
least two scheduled flights were waiting in Helsinki for the runway to be opened again. No
othereffectsonairtraffichavebeenreported.
1.2 Damagetoaircraft
Theaircraftwassignificantlydamagedintheareabetweentherightpropellerandtheinner
wingflapontheright-handside.
Asthefrontattachmentoftherightmainlandinggearfailed,thelandinggearlegwaspivoted
downandback,heldonlybytheaftattachment.Thedislocatedgeardamagedtheinnerwing
flap and the landing gear door. The wheel was clamped between the runway and the wing
flap,anditstyrewasabradedthrough.Theenginenacelle,wingskinplates,fairingsandtheir
bracketswerealsocrackedanddeformedinvariousplaces.
Therightpropellerandenginesustainedimpactdamage.Allpropellerbladeswerebent,and
abradedfromthetipssothattheywereabout70mmshorter.Thebladesweretwistedinto
anabnormalpositionwiththeirleadingedgesfacingbackward.
Thelandinggearendthatrubbedagainstthepavementduringlandingrunhadbecomesohot
thatitmeltedaholeintheasphaltwheretheplanestopped.Aboutonelitreofoilleakedto
therunwayfromtherightenginepropellerhub.Therewasnofire.
1.3 Personnelinformation
1.3.1 Pilots
Thepilotshadvalidclassandtyperatingsaswellasmedicalcertificatesasrequiredforthe
duty.
The pilot-in-command had a total flying experience of about 12675 hours on all aeroplane
typesandabout2010hoursonthetype.Theco-pilot’stotalflyingexperiencewasabout2426
hoursonallaeroplanetypesandabout2205hoursonthetype.
1.3.2 Technicalpersonnel
The first aircraft maintenance licence for the mechanic who had installed the right landing
gearwasissuedin1979.
Atthetimeoftheaccident,themechanicheldanEASA3Part66aircraftmaintenancelicence
includingan individualtype ratingforPiperPA-31piston-engineaeroplanesandgroupratingsforsmallsingle-enginepistonaeroplanes,andtheequivalentnationalrating.Thelicence
was valid until 8 February 2017 and contained category B1 and B2 ratings for the abovementionedtypes.
The mechanic had a limited certifying staff authorisation issued by Lapin Tilauslento Oy’s
EASA Part 145 maintenance organisation, which was valid for the aircraft type in question.
Theauthorisationhadbeenissuedforthefirsttimeon2June2015.Otherrequiredtypesof
trainingwerealsocurrent,includinghumanfactorstraining,whichhadbeenprovidedon30
September2015.
Themechanicwasfairlyexperienced,butwascarryingoutthisparticularmaintenanceaction
forthefirsttime.Accordingtohisownreporthewasalert,andthemaintenanceenvironment
andthetoolsusedwereappropriateandsuitableforthetask.Hedidnotfeelasbeingundera
timepressure.
3EuropeanAviationSafetyAgency
5
1.4 Aircraftinformation
Reims F406 is a low-wing aircraft with full metal construction, equipped with two Pratt &
WhitneyCanadaPT6A-112turbopropengines.IthasbeendevelopedfromCessna404Titan
piston-engineaircraft,andthefirstF406flewitsmaidenflightin1983.Theaircraftwasmanufactured by Reims Aviation, which alsoheldthe type certificate until year 2013,when the
companyceasedoperations.TodaytheaircrafttypecertificateholderistheFrenchcompany
ASIAviation.
Theaircraftisintendedforthecarriageofpassengersandfreight.Itisflownwithacrewof1–
2pilots,andthemaximumnumberofpassengersis9.
TheaccidentaircraftwasregisteredOH-OTLandmanufacturedin1986withtheserialnumber0015.Ithadbeenflownforatotalof11644hoursand15640flights.Themaximumcertificatedtake-offmassis4246kg.TheaircraftisownedbyOulunTilauslentoOyandoperated
byLapinTilauslentoOy.
Theaircraftcertificatesanddocumentsasrequiredforflightoperationswerevalid.Theaircrafthadbeenmaintainedinaccordancewithacurrentmaintenanceprogramme,andithad
beenreleasedtoserviceaftermaintenancejustbeforetheaccidentflight.
Theaircraftmassandbalancewereinthepermissiblerange.
1.4.1 Descriptionofthelandinggearsystem
The landing gear system is conventional and consists of hydraulically retractable nose and
mainlandinggear.Thisinvestigationfocusesonthemainlandinggear,whichisofanarticulated, trailing link type as shown in the picture. It is retracted and extended by a hydraulic
actuator,andisattachedbypivotpinsmountedonbearingstothefrontandaftwingspars.
When the pilot selects the landing gear up, the hydraulic valve in the landing gear system
opensandadmitspressuretotheactuator,openingtheinternaldownlockfirst.Theactuator
thenpullsthegearup.Whenthegearreachestheupposition,therolleronthesideofthegear
hitsthewheelwelluplock,whichgripstherollerandlocksthegearup.Thehydraulicvalve
closeswhenthegearisfullyupandlocked.
Wheneitherthelandinggearorawingflaphasbeenselectedtoanewposition,buthasnot
yetreachedtheselectedposition,theHYDPRESSONindicatorlightisilluminated.
Each landing gear has its own green indicator light, which islitwhen the individual gear is
downandlocked.Inaddition,thereisonecommon GEARUNLOCKEDwarninglightforallgears,
whichisilluminatedinredifanyofthegearsisnotsecuredinitsuplockordownlock.When
allgearsareintheiruplocks,allindicatorlightsareout.
Inthiscontextitmustbenotedthatthedownlockanditsstatusindicatorswitcharemounted
ontherelevantactuator.Aslongastheactuatorisinthelockedposition,thesystemindicates
thattheindividuallandinggearisdownandlocked.Thisisarathertypicalfeature.
6
Kuva1. Mainlandinggear.Picture:ASIAviation
1.5 Meteorologicalinformation
WeatherintheRovaniemi-Ouluareawasgood.Theplanetookoffintheeveningdusk,and
nightprevailedwhenitlandedatOulu.Visibilitywasgoodallthetime.
Weather at Rovaniemi at 18:20: wind 330° 8 kt, CAVOK4, temperature 5°C, dewpoint –2°C,
barometricpressureQNH51030hectopascal(hPa)
WeatheratOuluat19:50:wind350°7kt,CAVOK,temperature7°C,dewpoint0°C,QNH1032
hPa.
1.6 Aerodromeinformation
TheaccidentoccurredatOuluAirport,onthefirstsectionofrunway30.
1.7 Investigationoftheaccidentsiteandaircraft
Theinvestigationteamleaderarrivedattheaccidentsiteonthefollowingday,whentheaircrafthadbeenmovedfromtherunwaytothestandandraisedonjacks.Airportmaintenance
staffhadcheckedtherunwayconditiononthepreviouseveningaftertheaccident.
Theaccidentsitewasinspectedagaintorecordthemarksleftbytheaccidentaircraftandto
detectanyloosepartsontherunway.Noloosepartswerefound,exceptforafewrivetheads.
The aircraft wheel had lefta blackstreak and thelandinggeartrailinglinka slightmetallic
4
”CeilingandvisibilityOK”.ThecodewordCAVOKcanbeusedtoreplacethegroupsforvisibility,prevailingweatherand
clouds in a weather report when there are no operationally significantclouds or other meteorological phenomena. In
practice,thismeansaceilingofmorethan1500mandvisibilityover10km.
5 Altimetersub-scalesettingonwhichthemeterindicatesaltitudeabovemeansealevel
7
markontherunway.Rightenginepropellerbladeshadhittherunwayinthesameareawhere
theblackmarkleftbythetyrebegan.Thepropellerhadbeenrotatingduringtheentirelandingrun,leavingamarkeverytimeitstrucktherunway.Thedamagetotheaircraftwasphotographed,andthedamagedlandinggearwasremovedfromtheaircraftwhiletheinvestigatorwaspresent.Atthisstagethereasonforlandinggearfailurewasclearlyrevealed.
1.8 Medicalinformation
The pilots were subjected to a breathalyzer test after the accident. The test result was zero
bloodalcohollevel.Noothermedicaltestsweremade.
1.9 Rescueactionandsurvivalaspects
The pilot-in-command reported thelandinggear failure to ATC immediately after the plane
came to a stop. ATC alerted the rescue services of an aircraft accident at 20:05. The rescue
unitssecuredtheplaneandthesurroundingareaagainstfire.Thepilotswerenotinjured.The
aircraft was lifted up using pneumatic lifting pads and moved away from the runway on a
transportplatform.
Therunwaywasclosedforaboutthreehours,until23:00.
1.10 Detailedinvestigations
1.10.1Descriptionofmainlandinggearattachment,installation,andinstructions
Themainlandinggearisattachedtothewingmainlywithtwopivotpinslocatedfrontandaft
initsupperpart.Thelandinggearisremovedbypullingthepinsoffusingaspecialtool,and
thegear then separates from thewing.Beforethis,otherpartsofthegearandthesecuring
pinsthatlockthepivotpinsinplacemustberemoved(Figure2).
Kuva2. Main landing gear, withthe separatedpivotpin and the securing pin used to lock itin
placemarkedwithacircle.Theactuatorrodattachedtothelandinggearisshownunderthe
pivotpin.Picture:ASIAviation
Theforwardpivotpinisremovedbypullingitforwardinsidethewing.Toaccessthepin,an
accesspanelinthewheelwellmustbeopenedandthebleedairtubeinsidethewingdisconnectedtocreatemoreworkingspace.Theaccesspanelformsapartoftheload-bearingstructureandattachedwithseveralscrews(Figure3).
8
Kuva3. Forward attachment point of the right main landing gear in place. The location of the
pivotpinisshownbyaredrectangle.Thepivotpinisremovedandfittedthroughanopenaccesspanel.Picture:LapinTilauslentoOy
Wheninstallingthelandinggear,itisraisedtothecorrectpositionupinthewheelwell,and
supported there so that the pivot pin holes in the trunnion are in line with the articulated
bearingsonthewing.Thepivotpinsarethenfittedbypushingthemthroughthebearingsand
furthertotheirholesinthetrunnion.Operatingclearancebetweenthebearingandthetrunnionisadjustedbyusingasuitablenumberofshimwashers,throughwhichthepivotpinalso
passes.
The pivot pinnormally slides easily throughthebearing,andifthelandinggearisproperly
supported,alsotoitsholeinthetrunnion.Ifthelandinggearisnotsupported,moreforceis
neededtomovethepin.
Whenthegearisinplace,thepivotpinsarepositionedmoreaccuratelysothatthesecuring
pinholeonthepivotpinsislinedwiththecorrespondingholeinthetrunnion,andthesecuringpincanbefittedinplacethroughbothholes.Thesecuringpinisarollpin,whichisfurther
securedinplaceusingsafetywire.Inthiswaythepivotpinismechanicallysecuredtoprevent
axialmovement.
Thepivotpinsthusgothroughthearticulatedbearingsattachedtothewingstructure.When
thepinsarecorrectlyinplace,thetipoftheforwardpinremainsslightlyvisibleinfrontofthe
bearing.
Themountingdepthoftheaftpivotpinislimitedbythedepthoftheholeinthelandinggear
trunnion.Theforwardpivotpinhole,incontrast,extendsuntiltheverticalholeinthetrunnion,sothatthefittingpositionisnotmechanicallyrestricted.Forthisreason,especiallythe
forwardpinmustbepositionedcarefullytomakesurethatthesecuringpingoestoitsholein
thepivotpin,andnotbehindthewholepinaswhenthepivotpinisplacedtoofarforward.
Thecenterofthesecuringpinholeinthepivotpinislocatedabout16mmfromtheaftendof
thepin.
When fitted, the front end of the forward pivot pin can be seen with a mirror through the
wheelwellaccesspanel,andtheaftendwithamirrororsuitableborescopethroughtheverticalholeinthelandinggeartrunnion.Afterthesecuringpinisfitted,itcanbeseenfromthe
verticalholeifthesecuringpinhasbeenleftbehindthepivotpin.Propersecuringcanalsobe
checkedbytryingtopullthepivotpinwiththepullertoolwhilethelandinggearisbeingsupported.
9
Therearenoseparateinstructionsforthesechecks,asthemaintenanceinstructionsrelyon
theuseofgoodmaintenancepractices.
Themaintenanceinstructionsforlandinggearinstallationarefromyear1985.Theinvestigationrevealedshortcomingsinthem,andtheorderofactionswaspartlyimpractical.Forexample,theinstallationphasefortheaftpivotpinwasmissingentirely,andduringinstallation
of the forward pivot pin, it is instructed that the fitting tool be removed from the pivot pin
after the securing holes are aligned, but before the securing pin is fitted. The landing gear
functionaltestwasnotinstructedtobemadeafterinstallation,buttheplaneshouldonlybe
letdownfromthejacksontoitswheelsafterthelastinstallations.
1.10.2Historyofmaintenanceactions
Immediatelybeforetheaccidentflight,theaircrafthadbeensubjectedtophase20andphase
21 inspectionsof both main landing gears,forwhichthegearmustberemoved.Apart from
theneedforremoval,themaintenanceactionstakenhadnoimpactontheaccident.
Both landing gears were removed normally, and the required inspections for cracks were
madebyasubcontractor.Thetasksforgearremovalandinstallationweresharedsothatone
mechanic was in charge of the right landing gear and the other of the left. The mechanics
worked independently during installation without co-operating to a significant extent. The
mechanics’accountsofhowtheworkprogressedandofanyinformalreviewofeachother’s
workwereslightlydifferent.However,theaccountswereconsistentinthatsuchareviewwas
notcarriedoutonlandinggearattachments.
Whentherightlandinggearwasinstalled,theforwardpivotpinwaslefttoofarforwardso
thatthesecuringpinsupposedtogothroughitwaseventuallybehindthewholepivotpin.As
a result of the incorrect installation, nothing prevented the pivot pin from moving forward
andoutofthegeartrunnion.Thesecuringpinwasputinplaceandasafetywirewasinstalled
throughit.Accordingtothemechanicthatmadetheinstallation,heusedapunchtooltomake
surethatthesecuringholeforthepivotpinwasintherightplace.Whenpositioningthepivot
pin,hefirstnoticedthatthepunchdidnotgothroughthepivotpin,andrepositionedthepin
bysupportingthetrunnionwiththeotherhandandmovingthepivotpinwithapullertoolat
the same time. The punch then went throughthe hole in the trunnion, from which the mechanicassumedthattheholewascorrectlypositionedandfittedthesecuringpin.Whenremovingthepullertoolfromthepivotpin,hedidnotsupportthegeartrunnion,andbecauseof
greaterfrictionitseemedthatthepivotpinwaslockedinplace.
Afterthe accident,the mechanic hada veryclearimpressiononhowthemistakehadcome
aboutandthathehadaccidentallypulledthepivotpintoofarforwardwhenchangingitsposition.
Duringinstallation,however,themechanicwasleftwiththeimpressionthattheinstallation
wassuccessful,andnofurtherinspectionsweremade.
The installation of both landing gears had been identified as a critical task in maintenance
planning,andadoublecheck6asrequiredbyaviationregulationswascarriedout.Basedon
theinterviews,theattachmentsthemselveshadnotbeeninspected,butonlyageneralvisual
inspectionwasmade.
6
Forcriticalmaintenancetasks,aviationregulationsrequireadoubleinspectionofthetarget,wherethemechanicchecks
hisownworkasusualbutthenanotherinspectionismade,usuallybyanothermechanic.Thedoublecheckreducesthe
riskoferrorsinmaintenancework,butdoesnotnecessarilyeliminateitinallcases.
10
Inprinciple,landinggearinstallationisasimpleprocedureaslongasgoodmaintenancepracticeisfollowed.Theapprovedmaintenanceinstruction7isfairlyshort.Itcontainsonecaution
andtwonotes,neitherofwhichdrawsattentiontothepossibilityoferrorinthefittingofsecuringpins.Asregardspivotpinsandsecurings,theinstructionreadsasfollows:
(2)
Position trunnion in place and insert forward pivot pin ensuring washers
notedinstepAareinplaceandholesinpivotpinandtrunnionarealigned.
NOTE:
(3)
For minimum tire clearance maximum washer stack-up at fore
andaftendoftrunnionshallnotexceed0.350inch.
RemoveAN8Boltandflatwasher[pivotpinpullertool]frompivotpin.Install
pinintrunnionandpivotpin.Safetywirepinaroundtrunnion.
Theinstallationactionswerecompletedandtheaccesspanelinthewingwasclosed.
The maintenance instructions donotrequirealandinggearfunctionaltesttobeperformed
aftergearinstallation.However,thetestwascarriedoutatthemechanics’owndiscretionby
cyclingthegearupanddownseveraltimeswithoutproblems.
Theaircraftwasissuedwithacertificateofreleasetoserviceasusualandcheckedoutasairworthy.
1.10.3Post-accidenttechnicalinspectionoftheaircraft
Intheaircraftinspectionaftertheaccident,itwasfoundthatthepivotpinintheforwardattachment point of the rightmain landinggearhad partly slidoff itsplace. Thelanding gear
waspivotedbackduringthelandingrun,heldonlybytheaftattachmentandactuator.
Thepivotpinintheforwardattachmentpointwasnotattachedtothegeartrunnion,butinsteadtothewingbearing,fromwhichitwasremovedaftertheaccident.Thereweresuperficialmarksatthebackofthepivotpin,atadistanceofabout10mm(Figure4).Otherwisethe
pivotpinwasintact.
Thesecuringpinholeinthepivotpinwascoveredwithcleanassemblygrease.Onthetrunnionside,thesecuringpinwasintactandstillinitsplace,securedwithsafetywire(Figure5).
Otherdamageandanomaliesfoundhadresultedfromthecollapseofthelandinggear.
7MM32-10-00PageBlock400,revisionJul1/85,point3.B.
11
Kuva4. Theaftendoftherightmainlandinggearforwardpivotpin,photographedaftertheaccident.Thisendisattachedtothelandinggeartrunnion.Photo:LapinTilauslentoOy
Kuva5. Thesecuringpinoftherightmainlandinggearforwardpivotpininplaceaftertheaccident.Photo:LapinTilauslentoOy
1.11 Organisationalandmanagementinformation
LapinTilauslentoOyisanairlinecompanyandaircraftrepairstation,establishedin2003.It
operates one Reims F406 Caravan II turboprop aircraft and one Cessna 180 piston-engine
aircraft.Theplanesareusedforcharterflights,andtheF406alsoforambulanceflightsand
fortransportingmail.
ThecompanyholdsanAirOperatorCertificate8issuedbytheFinnishcivilaviationauthority
forcommercialairoperations,acontinuingairworthinessmanagementorganisationapprov
8EASA-OPSAOC
12
al9andanapprovalforlineandbasemaintenance10oftheaircraftitoperatesandothersimilaraircraft.Themaintenanceorganisationapprovalwasgrantedinautumn2015.
UndertheAOCofLapinTilauslentoOyoperatesthecompanyOulunTilauslentoOy,whichisa
commercialairoperatorestablishedin1992andbasedinOulu.Thelattercompanyownsthe
accidentaircraft,ReimsF406.ThemaintenanceorganisationandhangarsofLapinTilauslento
OyarelocatedatRovaniemiAirport.
The company maintenance organisation has three full-time employees – the accountable
manager,qualitymanagerandnominatedpostholderformaintenance.Allthreearenominated postholders also for the company’s air operations and in the continuing airworthiness
managementorganisation,andthequalitymanageristhecompanymanagingdirectoraswell.
Thenominatedpostholderformaintenancealsoactsasanaircrafttypemechanic.Inaddition,
themaintenanceorganisationemploysthreepart-timemechanics.
The investigation examined the maintenance organisation’s internal procedures, using both
internalqualitycontrolfindingsandauditobservationsmadebythecivilaviationauthority.
Theinvestigationdidnotrevealanyfactorsinthecompanyoperationsthatwouldhavecontributedtotheaccident.
Maintenanceorganisationmanagementwasnotinvestigatedduetoitslimitedsize.
Therewasnoneedtoinvestigatetheotherorganisations,astheydidnothaveanyeffecton
thesequenceofevents.
1.12 Otherinformation
Theinvestigatorssearchedthedatabasesofflightsafetyauthoritiesandsentanenquirytothe
aircrafttype certificate holder. Theaimwastofindoutwhethersimilarmaintenanceerrors
havebeenpreviouslyreportedfortheF406CaravanIIaircrafttype,orforCessna404Titan
thathasasimilartypeoflandinggear.
Based on the information obtained, some cases of pivot pin breaking loose due to maintenanceerrorshave beenreportedatleastforCessna404,resultinginmainlandinggearfailure.
9EASAPartMSubpartG&I
10EASAPart145
13
2 ANALYSIS
TheaccidentanalysisusedtheAccimapApproach11.Thestructureoftheanalysistextisbased
on the AcciMap graph prepared by the investigation group, which is attached separately as
Appendix1.
2.1 Accidentanalysis
2.1.1 Probleminlandinggearretraction
Aftertake-off,therightlandinggeardidnotengageintoitsuplock,andthewarninglightsfor
gearuplockandhydraulicsystemremainedon.
As the uplock indicator light is common for all landing gear, it does not show which of the
three gears isnotlockedup. Uplock failuremaytypicallybecausedbyanadjustmenterror,
mechanical jammingof theuplock,insufficientlubrication,orcontaminantssuchasicing. In
thiscase,thefailureoftherightmainlandinggeartoengageintoitsuplockpositionindicates
thatthegeargeometryhadalreadychanged,eventhoughtheforwardpivotpinmaystillhave
beenpartlyattachedtothelandinggeartrunnion.
Thepilotsselectedthelandinggearbackdown.Thewarninglightsthenextinguishedandthe
three green lights for the landing gear illuminated, indicating that the gear was down and
locked.The HYDPRESSONwarningalsowentoff,anditseemedthatthelandinggearwouldbe
normallyextended.
The landinggearsystem is designedsothatthemainlandinggeardownlockisfittedto the
hydraulicactuatorthatdrivesthegear.Forthisreason,thedownlockindicatorlightactually
onlyshowsthestatusoftheactuator.Thefactthatthedownlockindicatorlightcameonindicatesthatthelandinggearhydraulicandelectricalsystemswerestillintact.
2.1.2 Actionsandtrouble-shootinginflight
According to the information availabletothepilots,thelandinggearwassafelydown.Gear
retractionhadfailed,butjudgingfromtheindications,ithadsettledintothedownlockswithoutproblems.Nounusualnoiseswereheard,soitcouldbeassumedthatthefaultwasinthe
landinggearhydraulics,orpossiblytherewasamechanicalfaultoranindicationerrorinone
ofthethreeuplocks.
Although the situation was abnormal, nothingsuggested an actual emergency. The weather
wasgoodanditwasashortflightfromRovaniemitoOulu,sothepilotsdecidedtocontinue
flyingtowardsOuluwiththegearextended.However,thepivotpininthelandinggearfront
11 TheAcciMapApproachisusedinanalysingcontributingfactors,findingthemostimportantconclusionsaswellasfor
preparingeffectivesafetyrecommendationsandtargetingthemtotherightentities.
TheaccidentisdepictedasachainofeventsatthebottomoftheAcciMapgraph.Identifieddecision-makersandother
levelsthatguideactionaremarkedontheleftside.Thedifferentelementsofthechainofeventsareshownasabottomto-topsequence.Thelowerpartofthegraphportraysanassessmentoftheindividualaccidentwhichisbeingstudied,
fromwhichtheprocessleadstowiderperspectivesandimplications,forexample,atthenationalorinternationallevel.
TheanalysistextfollowstheAcciMapgraphandprovidesmoredetailedbackgroundforindividualtextboxesandtheir
interconnections.Theanalysisofactionstakenbyauthorities,asrequiredbytheSafetyInvestigationAct,isdoneseparatelyasnecessary.
SourcefortheAccimapprocedure:J.RasmussenandI.Svedung,2000,ProactiveRiskManagementinaDynamicSociety,
SwedishRescueServicesAgency,Karlstad,Sweden.
14
attachmentwaslooseorabouttobreakloosefromthegeartrunnion.Whenfullyseparated,
thepinfallsdowninsidethewing.
2.1.3 Landinggearfailure
Whenthelandinggearwasinstalledduringmaintenancebeforetheflight,thepivotpinwas
lefttoofarforward.Thesecuringpinthatwasintendedtosecurethepivotpinhadbeenfitted, but entirely behind the pivotpin. The securing pin shouldpass through theholein the
pivotpin,sothatthepinismechanicallylockedinplace.Becauseofincorrectinstallation,the
pivotpinwasfreetomoveforwardandoutofitsplace.Evenatmost,thepivotpinwasonly
about10mminsidethegeartrunnion.
Duringtaxiingfromthestandtotake-off,thepivotpinwassubjectedtovibration,whichreducedfriction and alsocreated forcesthatmadethepinmoveforwardoutofitsplace. The
pivotpinseparatedfully fromthe landinggeartrunnionatthelatestwhenthepilotstarted
brakinguponlanding.
After the pivot pin came loose from the trunnion itremained attached to thewing bearing,
fromwhichitwasremovedaftertheaccident.Thepivotpinwasintactapartfromsomesuperficialmarks.
Whenmaintenanceworkbeforetheflightwasstarted,themechanicremovedtherightmain
landinggear.Attheendoftheworkhereinstalledthesamegear.Themechanichadnopreviousexperienceofthetaskinquestion,buthehadapprovedmaintenanceinstructions,proper
toolsandsuitableworkingconditionsathisdisposal.
Theworkdocumentsshowedthattheinstallationofbothlandinggearshadbeenidentifiedas
acriticaltaskinmaintenanceplanning,andadoublecheckhadbeencarriedoutasrequired.
However,thedoublecheckdidnotspecificallyfocusonthefittingofthepivotpin.
The maintenance instructions are from year 1985, and in many parts, only based on good
maintenancepractice.Forexample,theinstructionsprovidenowarningofthepossibilityof
incorrectsecuringpininstallation,oradvisethatthesecuringshouldbecheckedafterthepin
isfitted,althoughsuchacheckwouldbeimportantandeasytoperform.
Inaddition,the orderofactionsrecommendedintheinstructionsisimpractical,asthey advise toremove the puller tool used forpositioningimmediatelyafterthesecuringholes are
aligned,beforethesecuringpinisfitted.Unscrewingofthepullertoolincreasestheriskofthe
pivotpinmovingtoanincorrectposition.Thereforethesecuringpinshouldbefittedassoon
astheholesareverifiedtobealigned.
Essentialproceduresarealsomissingfromtheinstructions,suchasthefittingoftheaftpivot
piningeneral,andthelandinggearfunctionaltestafterinstallation.
Nevertheless,themaintenanceorganisationhadunderstoodthatfunctionaltestofthelanding
gearwouldbeappropriateaftersuchmaintenance.Thisshowsthattheorganisationhadthe
ability to independently identify risks and to strive towork in a correct manner. It was observed that the organisation uses the risk assessment process in an active and documented
waytosupplementmaintenanceinstructionswhentheyarefoundinadequate.
The landing gear functional test was carried out by cycling the gear up and down several
times without problems. Nothing suggested a latent error, so the aircraft was issued with a
certificateofreleasetoserviceasusualandcheckedoutasairworthyaftermaintenance.
15
2.1.4 Rescueaction
Aftertheplanecametoastop,thecrewreportedtheincidenttoATCandaskedforatowvehicle.Thecrewwasnotinjured.
Theairtrafficcontrollermadeareportofanairtrafficaccidentandalertedrescueservices.
Emergencyresponsewassufficient.Noactualrescueactionwasneeded,butOuluAirportwas
closedtoothertrafficforthreehoursbecauseofclearancework.
16
3 CONCLUSIONS
3.1 Findings
1. Theaircraftwasairworthyinaccordancewithapplicableairworthinessrequirements
whendepartingfortheflight.
2. Thepilotsandmechanicswereappropriatelytrained,andtheirlicencesandqualificationswerevalid.
3. Whenthepilotsselectedgearupaftertake-off,theGEARUNLOCKEDwarninglightandthe
HYDPRESSONindicatorlightforthehydraulicsystemremainedon.
4. The gear lever was selected back down, and all three green indicator lights for the
landinggearwereilluminated.
5. Procedures directly applicable tothisparticularfaultsituationwerenotfoundin the
emergencychecklists.
6. Thepilotsusedtheprocedureintendedforsituationswherethe HYDPRESSONlightremainedoncontinuously.Thishelpedtolocatetheprobleminthelandinggearsystem,
butthenatureofthefaultwasnotrevealed.
7. Asthesituationdidnotrequireturningbackforlandingassoonaspossible,thepilotin-commanddecided to continuetheflighttoOuluwiththegearextendedandto examinetheprecisecauseofthemalfunctionthere.
8. Thecrewdidnotnoticeanyadditionalorabnormalnoisesbeforethelandinggearcollapsed.
9. AfteranormallandinginOulu,theaircraftstartedtotilttotherightassoonasthepilotstartedbraking.
10. Afterthelandinggearfailed,thepilot-in-commandmanagedtokeeptheplaneonthe
runwaybybrakinghardwiththeleftwheelbrake.Theplanecametoahaltattherunwayedgeafterabout80m.
11. Nightprevailedattheairport,andtheairtrafficcontrollerdidnotseethatthelanding
wasabnormal.
12. Thepilot-in-commandreportedtheincidenttoATCandaskedforatowvehicle.
13. Therunwaywasclosedforthreehoursduetoclearancework.
14. Immediately before this flight, the aircraft had undergone scheduled landing gear
maintenanceinwhichthemainlandinggearhadbeenremoved.Themechanicwhoinstalledtherightmainlandinggearhadnotcarriedoutthismaintenanceprocedurebefore.
15. Thetechnicalinvestigationrevealedthatthepivotpinintheforwardattachmentpoint
forthemainlandinggearhadslidoutofitsplace.Thesecuringpinandsafetywireintendedtosecurethepivotpinwereinplaceandundamaged.
16. The securing pin fittingholeinthepivotpinwasfilledwithgrease.Thesecuring pin
hadnotbeeninitscorrectplaceinsidethepivotpin,buthadbeeninstalledbehindit.
17
17. Wheninstallingthesecuringpin,themechanichadtosupportthelandinggearwithhis
hands to move the pivot pin and align the securing pin hole with the gear trunnion.
Withoutthemechanicnoticing,thepivotpinhadslidtoofarforward.
18. Themechanicfittedthesecuringpinwithoutmakingsurethatthepivotpinwascorrectlyinstalled.
19. Installation instructions forthepivotpinandsecuringpinprovidenowarningof the
possibilityofincorrectinstallation.
20. The landing gear installation instructions do not cover all necessary phases of work,
andtheorderofphasesisimpracticalinsomeplaces.
3.2 Probablecauses
Theaccidentwascausedbyaninstallationerrorintherightmainlandinggear.Checksmade
duringinstallationwereinadequate,andeventhefinalinspectionoftheworkdidnotcover
thecorrectfittingorsecuringofthepivotpin.
Thepivotpininstallationprocedureisnotcomplex,andtheprincipleiseasytounderstand.
Workingconditionsweregoodandthemechanicwhofittedthepinwasfairlyexperienced,so
a clear and explicit cause for the error couldnot be determined. Even though this phase of
installationwasimportantstructurallyandforflightsafety,onesignificantpossibilitymaybe
thatthemechanic’sconcentrationwasnotfocusedontheseeminglysimpletask.
Acontributingfactor to theerrorwasthatthemaintenanceinstructionsdidnotadequately
supportthecorrectperformanceandqualityassuranceofthework.
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4 SAFETYRECOMMENDATIONS
4.1 Safetyactionsalreadyimplemented
LapinTilauslentoOyhas,on9January2017,madeananalysisofthesequenceofeventsleadingtotheaccident,andpreparedalistofactionstoimproveworkplanning,inspectionproceduresand the company’s internalinstructions.ThecompanyhasalsoprovidedHuman Factorsrefreshertrainingtoitsstaffduetotheincident.Inaddition,itisplanningtomakemore
extensive changes to itsmaintenance organisationexposition,withafocusonqualityassuranceandcriticalmaintenancetasks.
4.2 Safetyrecommendations
4.2.1 ReviewofmaintenanceinstructionsforReimsF406CaravanIIaircraft
ASIAviationisthecurrenttypecertificateholderfortheaircraft,andaccordingtotheinformationonitswebsite,isplanningtorestartitsproduction.Toensurethatbothexistingaircraftandanynewaircrafttobemanufacturedcanbesafelymaintained,itisnecessarytoat
leastcorrect the errors detectedandreviewthemaintenancemanualsforanyothersimilar
inaccuracies.
TheSafetyInvestigationAuthority,Finlandrecommendsthat
TheEuropeanAviationSafetyAgency(EASA)requiretheaircrafttypecertificateholder
toreviewandupdatethemaintenanceinstructionsforReimsF406aircraft,sothatany
deficienciesinmainlandinggearinstallationinstructionsarerectified.Thelandinggear
installationinstructionsdonotcoverallnecessaryphasesofwork,andtheorderofphasesisimpracticalinsomeplaces.Theinstructionsprovidenowarningofthepossibilityof
incorrectpivotpininstallation.[2017-S26]
Incorrectorinsufficientinstructionsdonotadequatelysupporttheperformanceofthework.
Theriskofmaintenanceerrorsincreasesandflightsafetyiscompromised.
4.2.2 ReviewofmaintenanceinstructionsforotherCessnamodels
TheReimsF406aircrafttypeisbasedonCessna404.Bothaircrafthavethesamelandinggear
construction, and maintenance instructions may also be partly the same. The same landing
gearmodelmayhavebeenusedinotheraircrafttypesmanufacturedbyCessna.
TheSafetyInvestigationAuthority,Finlandrecommendsthat
TheFederalAviationAdministration(FAA)oftheUnitedStatesrequiretheaircrafttype
certificateholderto reviewand,wherenecessary,updatethemaintenanceinstructions
forCessna404andanyotheraircrafttypeswithatrailinglinklandinggear,sothatany
deficienciesfoundinmainlandinggearinstallationinstructionsarerectified.Thelandinggearinstallationinstructionsmaynotcoverallnecessaryphasesofwork,andtheorderofphasesmaybeimpracticalinsomeplaces.[2017-S27]
19
Helsinki,10.5.2017
IsmoAaltonen
PekkaAlaraudanjoki
20
JanNordlund
REFERENCEMATERIAL
ThefollowingreferencedocumentsarearchivedattheSafetyInvestigationAuthority,Finland.
1. Decisiontoinitiateaninvestigation
2. FlightsafetyreportfiledbythepilotsofOH-OTL
3. Flightsafetyreportfiledbytheairtrafficcontroller
4. Policeinvestigationreport
5. MaterialprovidedbyFinaviaOyj
6. Emergencyandaccidentdescription
7. ReimsF406maintenancemanualandillustratedpartscatalog
8. MaterialprovidedbytheFinnishTransportSafetyAgency
9. DocumentsfromLapinTilauslentoOy
10. NTSBinvestigationreports
11. Photographsfromtheaccidentsiteandinvestigations
12. Recordingsofinterviews
13. E-mailcorrespondence
21
SUMMARY OFTHE COMMENTS RECEIVEDON THEDRAFTINVESTIGATION
REPORT
CommentsonthedraftinvestigationreportwererequestedfromtheFinnishTransportSafety
Agency,FinaviaCorporation,LapinTilauslentoOyandASIAviation,aswellasfromtheEuropeanAviationSafetyAgency(EASA),TheBureauofInvestigationandAnalysisforCivilAviation Safety (BEA) of France, the Federal Aviation Administration (FAA) of the United States
andtheNationalTransportationSafetyBoard(NTSB)oftheUnitedStates.
Lapin Tilauslento Oy did not wish to add anything to the draft report, but clarified some
pointsabouttheactionsthatwillbetakenatthecompanyduetotheincident.
The Bureau of Investigation and Analysis for Civil Aviation Safety (BEA), praised the
draftreportasawholeandagreedwithbothrecommendations,statingthattheywereappropriately directed. BEA’s request for further information has been taken into account in the
finalinvestigationreport.
TheEuropeanAviationSafetyAgency(EASA)hadnocommentsonthedraftreport.
TheFinnishTransportSafetyAgencyhadnocommentsonthedraftreport.
The Federal Aviation Administration (FAA) did not submit official comments, but stated
thatitwouldwaitforthefinalreportbeforetakinganyfurtheraction.
Theotherorganisationsdidnotrespondtotherequestforcommentswithinthetimelimit.
22