wolfgang loppitsch stamp modeling of the accident n4252g
TRANSCRIPT
VehicleSafetyInstitute
WolfgangLoppitsch
STAMPModelingoftheAccident
N4252G
MASTER’STHESIStoachievetheuniversitydegreeof
MasterofEngineering
Master’sDegreeProgram:TrafficAccidentResearch-AviationSafety
Submittedto
GrazUniversityofTechnology
Supervisors: Priv.-Doz.Dr.IoanaKoglbauer
Ao.Univ.-Prof.Dr.techn.ReinhardBraunstingl
VehicleSafetyInstitute
Graz,March,2019
TUGrazIMasterthesis
AFFIDATIV
IdeclarethatIhaveauthoredthisthesisindependently,thatIhavenotusedotherthanthedeclared
sources/ resources, and that I have explicitly marked all material which has been quoted either
literally or by content from the used sources. The text document uploaded to TUGRAZonline is
identicaltothepresentmaster‘sthesis.
Graz,March29,2019 _________________________________
Signature
TUGrazIMasterthesis
Preface
I
PREFACE
Followingalonginterest inaviationsafety, IhaveattendedtheMaster’sDegreeProgramofTraffic
AccidentResearch-AviationSafetyattheUniversityofTechnology,Graz,Austria.
Myexperienceasaprofessionalpilot ranges fromsingle-enginepistonaircraft via theBombardier
Global Express long-range corporate aircraft to the Airbus A320 type. Besides, I have gained
experienceasaflightoperationsofficer,aflightinstructor/examinerforsingle-enginepistonaircraft,
a type-rating instructor/ examiner and flight operations inspector for the Austrian Civil Aviation
Authority.
Reoccurringcasesofrathersimilaraircrasheswithsingle-enginepistonaircrafthaveinitiatedvarious
discussions about the model-based improvement of accident investigation processes used for
modernGeneralAviationaircraft,whichhaveledtothedevelopmentofthisthesis.
Atthisfinalstageofmystudies,Iwouldliketotaketheopportunitytothankmyfamilyandfriends
forsupportingandencouragingmetocontinuetowardsmyacademicgoals.Finally, Iwould liketo
thankmyacademicsupervisorsfortheirkindhelpandsupportduringthedevelopmentofthisthesis.
TUGrazIMasterthesis
Abstract
II
ABSTRACT
Thepresentmaster'sthesisaimstocomparetheresultsofatraditionalaccidentinvestigationreport
publishedby the investigatingparty (NTSB)anda system-theoreticalmodelingbasedonLeveson’s
STAMPmodelandCASTmethodology(Leveson,2011).
Today’s accident analyses reports are often based on linear accident models that allow the
identification of only a limited number of causes, and safety recommendations for avoiding such
accidents in the future. The accident ofN4252Gwas published in great detail via socialmedia by
meansofphotosandvideorecordings.Theassociatedcausesresultingfromtheaccidentreport,and
thesafetyrecommendationsdidnot includeallthelessonsthatcouldbelearntfromthisaccident.
Thus,themotivationwasgiventosystemicallymodelthisaccidenttoprovideasystemicviewofits
causes.
OnJune9,2016,aCirrusSR20registeredaircraftcrashedatWilliamPHobbyAirport(HOU),Texas,
USA,andallthreepersonsonboardlosttheirlives.ThepilottriedseveraltimestolandinHOU.The
firstapproachwascancelledbyATCforsubsequentcommercialairtraffic.Theaircraftremainedon
towerfrequencyunderhigh-trafficsituations.ThesecondlineupforapproachwascancelledbyATC.
Twomoreapproacheswereexecuted,whichallendeduptoohighanddidnotallowasafelanding.
During the lastgo-aroundprocedure, theATCcontrollerwas relieved.Thepilot lost controlof the
aircraft at about 500ft above ground level, causing a spin. The aircraft impacted in anempty car,
whichwas parked near a hardware store. The accident site was located about half amile of the
approached runway. The weather was characterized by good visibility and strong and gusty
crosswindsupto20kts.
Considering a list of relevant definitions, the most important facts referring to the accident and
technicalaspectsoftheaircraftweresummarizedintheappendicesofthisthesis.Thetimelimitof
theanalysiswasdefinedfromthefirstcontactwithHOUATCuntiltheaccident.Theanalysisofpost-
crasheventswasexcluded.Fordetailedillustration,relevantstoredflightdataoftheon-boarddata
module and position logs from radar data were presented graphically together with the time-
referenced ATC transmissions. Using the Systems-Theoretic Accident Model and Process STAMP
(Leveson,2011),thisthesisproposesanSTPA-basedmodeloftheaccidentthatincludesthecontrol
structures of ten individual system components, unsafe control actions, dysfunctional interactions
and contextual factors. The STAMP-based model of the accident allowed to generate 55 safety
recommendationsand64raisedquestions.TheresultsillustratetheexistingpotentialofSTAMPand
CAST (Leveson,2011) for improvingtheaviationaccident investigationandshowsthat thepresent
aviationaccidentcouldbeinvestigatedandunderstoodinmoredetailbyapplyingSTAMPandCAST.
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TableofContents
III
TABLEOFCONTENTS
1 INTRODUCTION 2
1.1 Motivation 2
1.2 Objectives 2
2 STAMPANALYSISOFTHEN4252GACCIDENT 3
2.1 DefinitionofRestrictingConditionsandTimeLine 3
2.2 RadarDataandGraphicalPresentationofFlightData 4
2.3 GeneralDefinitionsforthePresentCASTAnalysis 42
2.4 GeneralModelofHierarchicalControlStructure 44
2.5 ProcessModelforeachSystemComponent 45
2.5.1 HigherControlLevel(HCL)-ControlStructure 46
2.5.2 TrainingOrganisation-ControlStructure 49
2.5.3 ATC-ControlStructure 51
2.5.4 AircraftManufacturer(Cirrus)-ControlStructure 56
2.5.5 COPA-ControlStructure 58
2.5.6 HOUAirport-ControlStructure 59
2.5.7 Operator/AircraftOwner-ControlStructure 60
2.5.8 Pilot-ControlStructure 61
2.5.9 Passengers-ControlStructure 66
2.5.10 Aircraft-ControlStructure 67
3 RESULTS 69
4 DISCUSSION 78
5 CONCLUSIONS 79
6 REFERENCES 80
APPENDIX A-1A
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TableofContents
IV
DefinitionofRelevantTerms A-1
APPENDIX B-1B
LossofControlinGeneralAviation B-1
APPENDIX C-1C
GeneralInformationaboutSTAMP C-1
HierarchicalControlStructure(HCS)inSTAMP C-2
APPENDIX D-1D
HistoryofFlightN4252G D-1
SummaryofBasicEventsofFlightN4252G D-2
Pilot-Information D-4
Pilot-ExperienceLevel D-5
APPENDIX E-1E
RelevantAspects-SR20PilotOperatingHandbook(POH) E-1
RelevantAspects-SR20FlightOperationsManual(FOM) E-6
APPENDIX F-1F
ResultsRaisedbytheNTSBFinalReport F-1
APPENDIX G-1G
ChainofEvents G-1
APPENDIX H-1H
InterviewswithATCControllersheldbyNTSB H-1
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TableofContents
V
APPENDIX I-1I
SummaryofCFIStatements I-1
APPENDIX J-1J
RecordedFlightData J-1
APPENDIX(SYSTEMCOMPONENTS) K-1K
APPENDIX(ILLUSTRATIONS) L-1L
APPENDIX(ATCTRANSCRIPT) M-1M
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ListofFigures
VI
LISTOFFIGURES
Figure2-1OverviewofN4252G’sgroundtrackinthevicinityofHOU...................................................4
Figure2-2Initialapproachtorunway4andATC-directedgo-around....................................................9
Figure2-3Maneuversfollowingtheinitialgo-around..........................................................................12
Figure2-4Continuedpatternmaneuvers.............................................................................................15
Figure2-5Continuedpatternmaneuvers.............................................................................................18
Figure2-6Changingapproachfromrunway4torunway35................................................................21
Figure2-7Settingupforinitialstraight-inapproachtorunway35......................................................24
Figure2-8Runway35firstapproachandgo-around............................................................................27
Figure2-9Preparingforsecondapproachtorunway35.....................................................................30
Figure2-10Downwindtofinalturn,secondapproachtorunway35..................................................33
Figure2-11Secondapproachtorunway35.........................................................................................36
Figure2-12Go-aroundfollowingsecondapproachtorunway35andlossofcontact........................39
Figure2-13Generalmodelofhierarchicalcontrolstructure...............................................................44
Figure2-14HCL-simplifiedcontrolstructure......................................................................................46
Figure2-15Trainingorganisation-simplifiedcontrolstructure..........................................................49
Figure2-16ATC-simplifiedcontrolstructure......................................................................................51
Figure2-17Aircraftmanufacturer-simplifiedcontrolstructure.........................................................56
Figure2-18COPA-simplifiedcontrolstructure...................................................................................58
Figure2-19HOUairport-simplifiedcontrolstructure.........................................................................59
Figure2-20Operator/Aircraftowner-simplifiedcontrolstructure....................................................60
Figure2-21Pilot-simplifiedcontrolstructure.....................................................................................61
Figure2-22Passengers-simplifiedcontrolstructure...........................................................................66
Figure2-23Aircraft-simplifiedcontrolstructure................................................................................67
Figure3-1Generalmodelofhierarchicalcontrolstructureincludingresults......................................77
Figure6-1HOUairportdiagram...........................................................................................................L-1
Figure6-2GuidanceforestablishingPersonalWeatherMinimums...................................................L-2
Figure6-3EnvelopeofSafety..............................................................................................................L-3
Figure6-4Windcomponentdiagram..................................................................................................L-4
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ListofTables
VII
LISTOFTABLES
Table2-1SummaryofATCtransmissions,12:52:47-12:57:02CDT......................................................6
Table2-2HCL-CASTanalysis................................................................................................................48
Table2-3Trainingorganisation-CASTanalysis....................................................................................50
Table2-4ATC-CASTanalysis................................................................................................................55
Table2-5Aircraftmanufacturer-CASTanalysis...................................................................................57
Table2-6COPA-CASTanalysis.............................................................................................................58
Table2-7HOUairport-CASTanalysis..................................................................................................59
Table2-8Operator/Aircraftowner-CASTanalysis.............................................................................60
Table2-9Pilot-CASTanalysis...............................................................................................................65
Table2-10Passengers-CASTanalysis..................................................................................................66
Table2-11Aircraft-CASTanalysis........................................................................................................68
Table3-1Safetyrecommendations......................................................................................................74
Table3-2Questionsraised....................................................................................................................77
Table6-1SummaryofATCtransmissions,12:57:02-13:08:45CDT.................................................M-2
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ListofDiagrams
VIII
LISTOFDIAGRAMS
Diagram2-1Visualdescentangledirecttotheaimingpoint,12:27:56-12:56:30CDT........................6
Diagram2-2Graphicaldepictionofbasicflightdata,12:27:48-12:56:32CDT.....................................7
Diagram2-3Visualdescentangledirecttotheaimingpoint,12:56:54-12:58:07CDT........................9
Diagram2-4Graphicaldepictionofbasicflightdata,12:57:02-12:58:06CDT...................................10
Diagram2-5Visualdescentangledirecttotheaimingpoint,12:57:55-12:59:07CDT......................12
Diagram2-6Graphicaldepictionofbasicflightdata,12:58:04-12:59:04CDT...................................13
Diagram2-7Visualdescentangledirecttotheaimingpoint,12:58:55-13:00:06CDT......................15
Diagram2-8Graphicaldepictionofbasicflightdata,12:59:05-13:00:00CDT...................................16
Diagram2-9Visualdescentangledirecttotheaimingpoint,12:59:54-13:00:54CDT......................18
Diagram2-10Graphicaldepictionofbasicflightdata,12:59:59-13:00:47CDT.................................19
Diagram2-11Visualdescentangledirecttotheaimingpoint,13:00:42-13:01:42CDT....................21
Diagram2-12Graphicaldepictionofbasicflightdata,13:00:47-13:01:52CDT.................................22
Diagram2-13Visualdescentangledirecttotheaimingpoint,13:01:42-13:02:54CDT....................24
Diagram2-14Graphicaldepictionofbasicflightdata,13:01:52-13:02:52CDT.................................25
Diagram2-15Visualdescentangledirecttotheaimingpoint,13:02:54-13:04:07CDT....................27
Diagram2-16Graphicaldepictionofbasicflightdata,13:02:53-13:03:57CDT.................................28
Diagram2-17Visualdescentangledirecttotheaimingpoint,13:03:55-13:05:55CDT....................30
Diagram2-18Graphicaldepictionofbasicflightdata,13:03:56-13:05:50CDT.................................31
Diagram2-19Visualdescentangledirecttotheaimingpoint,13:05:43-13:07:06CDT....................33
Diagram2-20Graphicaldepictionofbasicflightdata,13:05:50-13:07:00CDT.................................34
Diagram2-21Visualdescentangledirecttotheaimingpoint,13:06:54-13:08:07CDT....................36
Diagram2-22Graphicaldepictionofbasicflightdata,13:06:59-13:07:59CDT.................................37
Diagram2-23Visualdescentangledirecttotheaimingpoint,13:07:55-13:09:07CDT....................39
Diagram2-24Graphicaldepictionofbasicflightdata,13:08:00-13:09:02CDT.................................40
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ListofAbbreviationsandCodings
IX
LISTOFABBREVIATIONSANDCODINGS
AC AdvisoryCircular(FAA)
AFM AirplaneFlightManual
AGL abovegroundlevel
AIM AeronauticalInformationManual
AltB BarometriccorrectedAltitudein[feet]aboveMSL
AME AeronauticalMedicalExaminer
APS AircraftParachuteSystem
ATC AirTrafficControl
ATCT AirTrafficControlTower
ATIS AutomatedTerminalInformationService
ATM AirTrafficManagement
ATSAP AirTrafficSafetyActionProgram
Avgas AviationGasoline(forspark-ignitedpistonengines)
CAPS CirrusAirframeParachuteSystem
CASTCausalAnalysisbasedonSTAMP
(Leveson,2011)
CD ClearanceDelivery(ATC)
CDM CriticalDecisionMakingseminar(byCOPA)
CDTCentralDaylightTime(UTCminus5)
in[hours]:[minutes]:[seconds]
CFI CertifiedFlightInstructor
CG CenterofGravity
CFR CodeofFederalRegulations(USA)
CHT CylinderHeadTemperature
COM ATCCommunicator(52G,LCI,LCTorLCC)
COPA CirrusOperatorPilotsAssociation
CPPP CirrusPilotProficiencyProgram(byCOPA)
CSIP CirrusStandardizedInstructorPilot
CTC CirrusTrainingCenter
TUGrazIMasterthesis
ListofAbbreviationsandCodings
X
Dist Distancein[NM]
DMS DocketManagementSystem
EGT ExhaustGasTemperature
FAA FederalAviationAdministration
FOM FlightOperationsManual
ft feet(1ftequals0.3048meters)
FD FlightData(ATC)
FITS FAAIndustryTrainingStandards
FLM FrontLineManager(ATC)
fpm feetperminute
GAJSC GeneralAviationJointSteeringCommittee
GA GeneralAviation
GC GroundControl
GGG GreggCountyAirport,Longview,Texas
GS GroundSpeedin[kts]
H Hazard
HCL HigherControlLevel
HLSC High-LevelSafetyConstraints
Hobby shortformforHOUairport
IFR InstrumentFlightRules
HCS HierarchicalControlStructure
HDG MagneticHeadingin[°]
HOU WilliamP.HobbyAirport,Houston,Texas
I90 HoustonTerminalRadarApproachControl
IAS IndicatedAirspeedin[kts]
ICAO InternationalCivilAviationOrganisation
ISA InternationalStandardAtmosphere
kgs kilograms
KIAS IndicatedAirspeedin[kts]
kts knots[1ktisequalto1NMperhour]
L Loss
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ListofAbbreviationsandCodings
XI
lbs pounds[1lbisequalto2.2kgs]
LC LocalControl(ATC)
LCC LocalControl–Controller(ATC)
LCT LocalControl–Trainee(ATC)
LCI LocalControl–Instructor(ATC)
LDA LandingDistanceAvailable
LOC LossofControl
mile equaltonauticalmile[NM]
MSL meansealevel
NM NauticalMile[1NMequals1852metersequals6076ft]
NATCA NationalAirTrafficControllersAssociation
NTSBNationalTransportationSafetyBoard
(investigatingparty)
OJT on-the-jobtraining
OJTI on-the-jobTrainingInstructor(ATC)
OUN UniversityofOklahomaWestheimerAirport
PAPI PrecisionApproachPathIndicator
Paxe Passengers
PD Policedepartment
PIC Pilotincommand
POH Pilot’sOperatingHandbook
PRC PerformanceRecordsofConference
QR Questionsraised
RadarAltitude AltitudeindicatedonATCradarmonitorin[ft]
RDM RecoverableDataModule
REC Recommendation
RPM revolutionsperminute
RY Runway
SA SituationalAwareness
SC SafetyRequirementsandConstraints
SRM Single-PilotResourceManagement
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ListofAbbreviationsandCodings
XII
SSR SecondarySurveillanceRadar
STAMP SystemsTheoreticAccidentModelingandProcesses(Leveson,2011)
STARS StandardTerminalAutomationReplacementSystem
STPA System-TheoreticProcessAnalysis(Leveson,2011)
SWA SouthwestAirlines
TAA Technologically-AdvancedAircraft
TCI TrainingCenterInstructor
TrOrg TrainingOrganisation
UCA UnsafeControlAction
US UnitedStates
US-gal USgallon[1US-galequals3.785liters]
UTC UniversalTimeCoordinated(generalmeantime)
Vfe maximumflapsextendedspeedin[kts]
Vno maximumnormaloperatingspeedin[kts]
Vs Stallspeedin[kts]
Vs0
“minimumsteadyflightspeedinthelandingconfiguration”(USDepartmentofTransportation,Pilot’sHandbookofAeronauticalKnowledge,2016,p.8-9)in[kts]
Vy“bestrateofclimbspeed”(USDepartmentofTransportation,Pilot’sHandbookofAeronauticalKnowledge,2016,p.G-34)in[kts]
VFR VisualFlightRules
VMC VisualMeteorologicalConditions
WINGS FAAPilotProficiencyProgram
x-wind cross-wind
52G ATCshortformforN4252G
Aspects that theauthorof this thesisconsidersassafetyrelevant for themodelingof theaccident
N4252GusingSTAMP(Leveson,2011)areunderlinedthroughouttheprevailingdocument.
TUGrazIMasterthesis
Introduction
1
“Thereisalmostnohumanactionordecisionthatcannotbemadetolookflawedinthemisleading
lightofhindsight.Itisessentialthatthecriticshouldkeephimselfconstantlyawareofthatfact.”
SirAnthonyHiddenQC(March7,1936–February19,2016)
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Introduction
2
1 INTRODUCTION
1.1 Motivation
After an aircraft accident, questions concerning what caused it are soon raised. The aeronautical
regulativesprovideaframeworkfortheinvestigation,althoughinmanycasesfinalaircraftaccident
reports endafter identifying causal humanerrors. Thus, opportunities aremissed to identify why
humans behaved in the way that they did and what preventive measures could prevent people
repeating the same errors in the future. The official investigation report of the N4252G accident
clearlydescribestheeventsandsomerelatedrootcauses.Theanalysisofwhythesehumanerrors
occurred could be enlarged using STAMP.Understanding that a human error is a symptom rather
thanacauseholdsutmostimportance,ashumansgenerallytendtobelievethateventsassuchare
moreobviousandpredictablethanbefore.Thisiscalled“hindsightbias”,whichmightultimatelyalso
influencetheobjectivityininvestigation.InthepresentaccidentreportofN4252G,theNTSBasthe
investigationboarddeterminedtheprobablecausessolelyashuman-affectederrors.Ashumansdo
not intentionallymakemistakes, the entiremental process inwhich context decisionsweremade
must be considered, as gaps in the safety control structure ultimately allow accidents to occur.
Consideringthathumanshaveacertaincapacityforperformingprocedures,itshallbenotedthatif
taskdemandsexceedapilot’scapability, theymayeitherbenotperformedproperlyorsomemay
notbeperformedatall.Thisunderstandingistheinitialstepofadetailedsystem-theoreticprocess
analysisandwasasignificantmotivationfactorforthedevelopmentofthisthesis.
1.2 Objectives
Theaimof this thesis is toconductadetailedanalysisof theN4252GaccidentbyapplyingSTAMP
(Leveson,2011).Incomparisontoconventionalstate-of-the-artinvestigationmethodsusedbymany
accidentinvestigationparties,thisthesisinvestigatestheapplicabilityofSTAMPforinvestigatingan
aircraft accident in systemic approach rather than on the analytical reduction approach that
considers the individual components. The focus of thismaster thesis is to systemicallymodel and
analyse complex control structures. The results shall highlight the potential of applying STAMP in
accidentresearchandshownewperspectivesoftheaccidentcauses,describeunsafecontrolactions
ofindividualcomponents,definegapsandopenquestionsfromtheofficial investigationandfinally
specify safety recommendations to address critical safety issues to avoid re-occurrences of similar
accidents.Theselectionofthisrelativeunknownaccidentasabaseforthethesisisdeliberate,asit
illustratestherequirementofmoderninvestigationmethodsforthewholeaviationsafetyspectrum.
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
3
2 STAMPANALYSISOFTHEN4252GACCIDENT
2.1 DefinitionofRestrictingConditionsandTimeLine
AsaninitialstepintheprevailingSTAMP(Leveson,2011)modeling,therestrictingconditionsofthe
aircraftaccidentofN4252GfromJune9,2016weredefinedbytheauthor.Thesystem-theoretictop-
down analysis starts at 12:27:48 CDT (when the pilot first contacted Houston Approach ATC) and
lasts until the impact. The post-crash events (e.g. rescue coordination) are excluded from the
analysis.Thedifficulty in theanalysisof thisaccidentwas thatpartiallycrucial informationneeded
forthefullunderstandingwasnotincludedinthefinalreportbytheinvestigatingparty.Itmustbe
noted,thatthisinformationappearsascrucialonlywhenSTAMPisbeingused.Thesequestionsare
listedinChapter3.
Themodeling of an accident according STAMP (Leveson, 2011) requires the specification of basic
eventsreferencedtothetime(“timeline”).This ispresentedinGAppendix inthesectionChainof
Events.
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STAMPAnalysisoftheN4252GAccident
4
2.2 RadarDataandGraphicalPresentationofFlightData
Asmentioned in theoriginal accident report, “Radardata for this accidentwasobtained from the
Standard Terminal Automation Replacement System (STARS) and from the Harris Opsvue radar
replay system licensed to the NTSB” (NTSB, Air Traffic Control, Group Chairman's Factual Report,
CEN16FA211,2016,p.7).Figure2-1showsanoverviewoftheaircraft’sgroundtrackinthevicinityof
HOU.
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.8)
Figure2-1OverviewofN4252G’sgroundtrackinthevicinityofHOU
Thegraphicalpresentationsof the flight trackwiththeassociatedATCtranscriptwereanalysedby
theauthortomodelthecomplexmaneuversoftheaircraftN4252Gbeforetheaccident.Itisbased
ontheplottedradarpositionsoftheN4252GRadarTargetFile1.
Figure 2-2 to Figure 2-12 illustrate the aircraft maneuvers in the vicinity of the airport with
annotationsfromtheATCtranscript(rf.(NTSB,AirTrafficControl,GroupChairman'sFactualReport,
CEN16FA211,2016,p.7)).
1TheN4252GRadarTargetFile-HOUASRGoogleEarthKMLTargetFilewasretrievedfromNTSBDMSWebsite:https://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=60618&CFID=2395938&CFTOKEN=81732fd00bba5423-5AB1BC7B-CB39-E91F-3732EB517FD2FBDB
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
5
When the ATC transcript in the ATC Factual Report (NTSB, Air Traffic Control, Group Chairman's
Factual Report, CEN16FA211, 2016) was compared with the HOU Tower Accident Package (HOU-
ATCT-0064,2018),theauthornoticedslighttimedeviations(inseconds),althoughitwasrecognized
thattheinfluenceforthefurtheranalysiswasneglectable.
Asmentioned in J Appendix, a selection of relevant flight data recordswas analysed at a physical
systemlevelbytheauthor.ThisdatawasimplementedintodiagramsfortheapplicationofSTAMP
(Leveson, 2011), seeDiagram2-1 toDiagram2-24. The engineparameters CHT and EGThavenot
been analysed, as the official NTSB investigation excluded any abnormal engine operation until
impact.Onlythepowerassetbythepilotwasconsidered.
Thefollowingabbreviationswereappliedforthegraphicalpresentation:
CDT Localtimereferencein[hours]:[minutes]:[seconds]
COM CommunicatorforATC-relatedtransmissions(52G,LCI,LCTorLCC)
Heading HeadingreferencedtoMagneticNorthin[°]
RY Anticipatedlandingrunwayforthepilot,asadvisedbyATC
___T Radaraltitudein[ft]
Ry4-Path Visual descent angle in [°] from aircraft position (based on actual radar altitude)
directtotheaimingpointofrunway4referencedtoAltB
Ry35-Path Visual descent angle in [°] from aircraft position (based on actual radar altitude)
directtotheaimingpointofrunway35referencedtoAltB
Pitch Aircraftpitchin[°],apositivepitchnumbermeansanose-upattitude
Roll Aircraftrollin[°],apositiverollnumbermeansaright-bankattitude
Power Powersettingin[%],rangingfrom0-100%
Flaps Flap setting [0, 1, 2], available flap settings correspond to numbers [0%=0, 50%=1,
100%=2]
AltB Barometriccorrectedaltitudein[ft]aboveMSL
HOUelevation 43ftaboveMSL
IAS Indicatedairspeedin[kts]
Vs Calculated2 stall speed (static) of SR20 in [kts] for the respective configuration
consideringloadfactor
Vfe/Vno IndicatesVfedependingonactualflapsconfigurationorVno 2ReferencestallspeedappliedforDiagram2-1toDiagram2-24(for0°bank)acc.POH-SR20(2015):69KIAS(forflaps0),65KIAS(forflaps50%),60KIAS(forflaps100%)(rf.(POH-SR202015,p.5-12)).
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
6
ThefollowingTable2-1summarizestheATCtransmissionsfrominitialATCcontactuntilthefirstgo-
aroundasretrievedfromtheHOUTowerAccidentPackageN4252G(2018).
CDT COM ATCTransmission/Note RY12:52:47 52G ThepilotcontactedtheHOUtowerLCpositionat1252:47andreportedat1600ft. 4
12:53:04 LCT Thetrainee(LCT)missedthesourceofthecallandthoughtitwasaSouthwestAirlines(SWA)flight.HerespondedasiftheSWApilothadcalled,thenrealizedthatithadactuallybeenthepilotofN4252G.
4
12:53:12 LCT Afterresolvingtheconfusion,theLCTtransmitted,“…you’renumber2followinga737ona3milefinal,cautionwaketurbulence,runway4clearedtoland”.
4
12:53:20 52G “WewillberunwayuhnumbertwofollowingtheBoeingrunway4clearedtoland…” 4
12:53:25 LCT “yesma'amandsayparking” 4
12:53:28 52G “We'llbeparkingMillionAir4252G” 4
12:53:51 LCI “Cirrus4252Gproceeddirecttothenumbers,you’regoingtobeinsidea737interceptinga10milefinal”
4
12:54:00 52G “OKyouwouldlikemetoproceedtothenumbers4252G” 4
12:54:04 LCI “November52G,whatdidapproachtellyoubefore?” 4
12:54:09 52G “Uh,tolandleftbaserunway4andfollowtheBoeing,4252G” 4
12:54:16 LCI “...proceeddirectthenumbersforrunway4,directtoHobby” 4
12:54:21 52G “DirecttoHobby,4252G” 4
12:54:24 I90 TheHobbyFinalcontrollercalledtheLCcontrollerstoaskthattheyhavetheCirrusproceeddirecttothenumbers,andtheLCIcontrollerrespondedthatthepilothadbeendirectedtodoso.
4
12:54:39 LCT TheLCTcontrolleraskedthepilottomaintainmaximumforwardspeedandproceeddirecttothenumbers,advisingherthattherewasa737on9milefinalfollowingtheCirrusthatwasovertakingitby80kts.Thepilotrespondedthatshewouldproceeddirecttothenumbersandkeepherspeedup.
4
12:55:49 LCT ThecontrollerbroadcastedtoallaircraftthatHOUATISinformationIndiawascurrent,altimeter29.94.ThepilotwasnotrequiredtoacknowledgetheupdatedATISannouncementanddidnotdoso.
4
12:55:59 LCT SWA235contactedHOU,reportingthattheywereon5milefinalforrunway4.TheLCTcontrollerrespondedthattheywerenumber2followingaCirruson2milefinal,clearedthepilottoland,andinstructedhimtoslowtofinalapproachspeed.
4
12:56:19 LCT windcheckof“080degreesat13ktsgustingto18kts”wasbroadcasted 4
12:57:02 LCI “justgo-aroundandflyrunwayheadingfornow,maintainVFR,andI’mgoingtoputyoubackonthedownwindforrunway35.Thewindsare090at13gusts18[kt].Canyouacceptrunway35?”
4
(rf.(HOU-ATCT-0064,2018,p.42,43,44)).
Table2-1SummaryofATCtransmissions,12:52:47-12:57:02CDT
Diagram2-1Visualdescentangledirecttotheaimingpoint,12:27:56-12:56:30CDT
0,00
2,00
4,00
6,00
8,00
10,00
12:27:56
12:30:08
12:30:56
12:31:44
12:32:32
12:33:20
12:34:08
12:34:56
12:35:56
12:36:56
12:37:44
12:38:32
12:39:32
12:40:20
12:42:07
12:43:19
12:44:19
12:45:31
12:46:19
12:47:07
12:47:55
12:48:43
12:49:31
12:50:42
12:51:30
12:52:18
12:53:18
12:54:06
12:54:54
12:55:42
12:56:30
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
7
Diagram2-2Graphicaldepictionofbasicflightdata,12:27:48-12:56:32CDT
-45-30-150153045
12:27:48
12:28:32
12:29:17
12:30:03
12:30:46
12:31:30
12:32:13
12:32:55
12:33:41
12:34:24
12:35:10
12:35:58
12:36:43
12:37:33
12:38:21
12:39:05
12:39:54
12:40:48
12:41:46
12:42:31
12:43:16
12:44:06
12:44:52
12:45:36
12:46:19
12:47:05
12:47:47
12:48:30
12:49:13
12:49:57
12:50:41
12:51:24
12:52:07
12:52:51
12:53:34
12:54:17
12:55:02
12:55:45
12:56:32
Pitch
-45-30-150153045
12:27:48
12:28:32
12:29:17
12:30:03
12:30:46
12:31:30
12:32:13
12:32:55
12:33:41
12:34:24
12:35:10
12:35:58
12:36:43
12:37:33
12:38:21
12:39:05
12:39:54
12:40:48
12:41:46
12:42:31
12:43:16
12:44:06
12:44:52
12:45:36
12:46:19
12:47:05
12:47:47
12:48:30
12:49:13
12:49:57
12:50:41
12:51:24
12:52:07
12:52:51
12:53:34
12:54:17
12:55:02
12:55:45
12:56:32
Roll
0
50
100
12:27:48
12:28:32
12:29:17
12:30:03
12:30:46
12:31:30
12:32:13
12:32:55
12:33:41
12:34:24
12:35:10
12:35:58
12:36:43
12:37:33
12:38:21
12:39:05
12:39:54
12:40:48
12:41:46
12:42:31
12:43:16
12:44:06
12:44:52
12:45:36
12:46:19
12:47:05
12:47:47
12:48:30
12:49:13
12:49:57
12:50:41
12:51:24
12:52:07
12:52:51
12:53:34
12:54:17
12:55:02
12:55:45
12:56:32
Power
0
1
2
12:27:48
12:28:32
12:29:17
12:30:03
12:30:46
12:31:30
12:32:13
12:32:55
12:33:41
12:34:24
12:35:10
12:35:58
12:36:43
12:37:33
12:38:21
12:39:05
12:39:54
12:40:48
12:41:46
12:42:31
12:43:16
12:44:06
12:44:52
12:45:36
12:46:19
12:47:05
12:47:47
12:48:30
12:49:13
12:49:57
12:50:41
12:51:24
12:52:07
12:52:51
12:53:34
12:54:17
12:55:02
12:55:45
12:56:32
Flaps
0
2000
4000
6000
12:27:48
12:28:32
12:29:17
12:30:03
12:30:46
12:31:30
12:32:13
12:32:55
12:33:41
12:34:24
12:35:10
12:35:58
12:36:43
12:37:33
12:38:21
12:39:05
12:39:54
12:40:48
12:41:46
12:42:31
12:43:16
12:44:06
12:44:52
12:45:36
12:46:19
12:47:05
12:47:47
12:48:30
12:49:13
12:49:57
12:50:41
12:51:24
12:52:07
12:52:51
12:53:34
12:54:17
12:55:02
12:55:45
12:56:32
AltB HOUelevauon
40,0
60,0
80,0
100,0
120,0
140,0
160,0
180,0
12:27:48
12:28:32
12:29:17
12:30:03
12:30:46
12:31:30
12:32:13
12:32:55
12:33:41
12:34:24
12:35:10
12:35:58
12:36:43
12:37:33
12:38:21
12:39:05
12:39:54
12:40:48
12:41:46
12:42:31
12:43:16
12:44:06
12:44:52
12:45:36
12:46:19
12:47:05
12:47:47
12:48:30
12:49:13
12:49:57
12:50:41
12:51:24
12:52:07
12:52:51
12:53:34
12:54:17
12:55:02
12:55:45
12:56:32
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
8
The detailed analysis of the flight data and the graphical presentation of the aircraft’s flight
parametersinDiagrams2-1(12:27:56-12:56:30CDT)and2-2(12:27:48-12:56:32CDT)inrelation
totheATCtranscript inTable2-1(12:52:47-12:57:02CDT)forthefirstapproachofN4252Gwere
analysedindetail.
Itrevealsthatbetween12:35:34CDTand12:36:27CDTtheVnowasexceededbyupto3.7kts.This
is permitted in smooth flight conditions. As the conditions of turbulence could not be extracted,
exceeding the Vno cannot be considered as an unsafe control action. At 12:55:23 CDT, the pilot
selected the flaps to50%ataspeedof129.5KIAS, therebyexceedingVfeof119KIASby10.5kts.
Until12:55:28CDT, theVfe limitwasexceeded (considering theATC request to “keepspeedup”).
When selecting the flaps to 100% at 12:55:47 CDT, Vfe was exceeded by 2kts for 1 second. The
aircraft’s final approach speed was gradually decreasing but not deceeding the normal approach
speeds (83KIAS for flaps50%,78KIAS for flaps100%, forproceduraldetails refer toEAppendix),
which - togetherwith theminor flight path corrections and the visual descent angle of around 3
degreestotheaimingpointofrunway4-concludedthatstabilizedapproachcriteriawerefulfilled.
AccordingtotheCirrusEnvelopeofSafety(refertoLAppendix,Figure6-3EnvelopeofSafety),the
reportedwind (“080 degrees at 13kts gusting to 18kts”) exceeded3 the personalized x-wind limit
(windlimit15kts,x-windlimit5kts,maximumgust5kts)accordingtothePilot’sCapabilityCategory
(fordetails,refertoDAppendix).
3TheauthorofthisthesisrecalculatedthewindcomponentsconsideringFigure6-4Windcomponentdiagramasfollows:080°/13ktssteady(gustsupto18kts)equals10kts(gustsupto14kts)headwindand8kts(gustsupto11kt)crosswindforrunway4(041°runwaytrack).
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
9
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.9)
Figure2-2Initialapproachtorunway4andATC-directedgo-around
Diagram2-3Visualdescentangledirecttotheaimingpoint,12:56:54-12:58:07CDT
0,00
5,00
10,00
15,00
20,00
25,00
12:56:54 12:57:06 12:57:18 12:57:31 12:57:43 12:57:55 12:58:07
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
10
Diagram2-4Graphicaldepictionofbasicflightdata,12:57:02-12:58:06CDT
-45
-30
-15
0
15
30
4512:57:02
12:57:04
12:57:06
12:57:09
12:57:11
12:57:13
12:57:16
12:57:18
12:57:20
12:57:23
12:57:25
12:57:27
12:57:30
12:57:32
12:57:35
12:57:38
12:57:40
12:57:43
12:57:45
12:57:47
12:57:50
12:57:52
12:57:55
12:57:57
12:57:59
12:58:02
12:58:04
12:58:06
Pitch Roll
0
20
40
60
80
100
12:57:02
12:57:04
12:57:06
12:57:09
12:57:11
12:57:13
12:57:16
12:57:18
12:57:20
12:57:23
12:57:25
12:57:27
12:57:30
12:57:32
12:57:35
12:57:38
12:57:40
12:57:43
12:57:45
12:57:47
12:57:50
12:57:52
12:57:55
12:57:57
12:57:59
12:58:02
12:58:04
12:58:06
Power
0
1
2
12:57:02
12:57:04
12:57:06
12:57:09
12:57:11
12:57:13
12:57:16
12:57:18
12:57:20
12:57:23
12:57:25
12:57:27
12:57:30
12:57:32
12:57:35
12:57:38
12:57:40
12:57:43
12:57:45
12:57:47
12:57:50
12:57:52
12:57:55
12:57:57
12:57:59
12:58:02
12:58:04
12:58:06
Flaps
0
500
1000
1500
12:57:02
12:57:04
12:57:06
12:57:09
12:57:11
12:57:13
12:57:16
12:57:18
12:57:20
12:57:23
12:57:25
12:57:27
12:57:30
12:57:32
12:57:35
12:57:38
12:57:40
12:57:43
12:57:45
12:57:47
12:57:50
12:57:52
12:57:55
12:57:57
12:57:59
12:58:02
12:58:04
12:58:06
AltB HOUelevauon
40,0
90,0
140,0
12:57:02
12:57:04
12:57:06
12:57:09
12:57:11
12:57:13
12:57:16
12:57:18
12:57:20
12:57:23
12:57:25
12:57:27
12:57:30
12:57:32
12:57:35
12:57:38
12:57:40
12:57:43
12:57:45
12:57:47
12:57:50
12:57:52
12:57:55
12:57:57
12:57:59
12:58:02
12:58:04
12:58:06
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
11
Thedetailedanalysisof the flightdataand thegraphicalpresentationsof the flight trackwith the
associated ATC transcript in Figure 2-2 and the graphical presentation of the aircraft’s flight
parametersinDiagrams2-3(12:56:54-12:58:07CDT)and2-4(12:57:02-12:58:06CDT)inrelation
totheATCtranscriptfortheinitialapproachofN4252Gtorunway4wereanalysedindetail.
ItrevealsthattheapproachwascancelledbyATCat12:57:01byrequestingN4252Gtogo-around.
Uptothen,theaircrafthadbeenfulfillingstabilizedapproachcriteriaforlandingonrunway4.When
initiatingthego-around,maximumpowerforthego-aroundprocedurewasnotset(forprocedural
details, refer to E Appendix), which the author assumes as the pilot’s intention to maintain the
presentaltitude(AltB)ofapproximately500ftandavoidoverspeedconditionswithexcessivepower.
The flapswere retracted to 50% at 75 KIAS and to 0% at 83 KIAS,which iswithin safe limits and
accordingtothePOHprocedures(forproceduraldetails,refertoEAppendix).Questioningtheright
downwind for runway 35 at 12:57:48 CDT by the pilot shows that uncertainty about the ATC
intentionswaspresent.
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
12
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.10)
Figure2-3Maneuversfollowingtheinitialgo-around
Diagram2-5Visualdescentangledirecttotheaimingpoint,12:57:55-12:59:07CDT
0,00
5,00
10,00
15,00
20,00
12:57:55 12:58:07 12:58:19 12:58:31 12:58:43 12:58:55 12:59:07
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
13
Diagram2-6Graphicaldepictionofbasicflightdata,12:58:04-12:59:04CDT
-45
-30
-15
0
15
30
4512:58:04
12:58:06
12:58:09
12:58:11
12:58:13
12:58:16
12:58:18
12:58:21
12:58:23
12:58:25
12:58:28
12:58:30
12:58:32
12:58:35
12:58:37
12:58:39
12:58:42
12:58:44
12:58:47
12:58:49
12:58:51
12:58:54
12:58:56
12:59:00
12:59:02
12:59:04
Pitch Roll
0
20
40
60
80
100
12:58:04
12:58:06
12:58:09
12:58:11
12:58:13
12:58:16
12:58:18
12:58:21
12:58:23
12:58:25
12:58:28
12:58:30
12:58:32
12:58:35
12:58:37
12:58:39
12:58:42
12:58:44
12:58:47
12:58:49
12:58:51
12:58:54
12:58:56
12:59:00
12:59:02
12:59:04
Power
0
1
2
12:58:04
12:58:06
12:58:09
12:58:11
12:58:13
12:58:16
12:58:18
12:58:21
12:58:23
12:58:25
12:58:28
12:58:30
12:58:32
12:58:35
12:58:37
12:58:39
12:58:42
12:58:44
12:58:47
12:58:49
12:58:51
12:58:54
12:58:56
12:59:00
12:59:02
12:59:04
Flaps
0
500
1000
1500
12:58:04
12:58:06
12:58:09
12:58:11
12:58:13
12:58:16
12:58:18
12:58:21
12:58:23
12:58:25
12:58:28
12:58:30
12:58:32
12:58:35
12:58:37
12:58:39
12:58:42
12:58:44
12:58:47
12:58:49
12:58:51
12:58:54
12:58:56
12:59:00
12:59:02
12:59:04
AltB HOUelevauon
40,0
90,0
140,0
12:58:04
12:58:06
12:58:09
12:58:11
12:58:13
12:58:16
12:58:18
12:58:21
12:58:23
12:58:25
12:58:28
12:58:30
12:58:32
12:58:35
12:58:37
12:58:39
12:58:42
12:58:44
12:58:47
12:58:49
12:58:51
12:58:54
12:58:56
12:59:00
12:59:02
12:59:04
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
14
Thedetailedanalysisof the flightdataand thegraphicalpresentationsof the flight trackwith the
associated ATC transcript in Figure 2-3 and the graphical presentation of the aircraft’s flight
parameters in Diagrams 2-5 (12:57:55 - 12:59:07 CDT) and 2-6 (12:58:04 - 12:59:04 CDT) for the
maneuversfollowingtheinitialgo-aroundofN4252Grevealsthatnounsafecontrolactionshadbeen
performedbythepilot.
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
15
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.11)
Figure2-4Continuedpatternmaneuvers
Diagram2-7Visualdescentangledirecttotheaimingpoint,12:58:55-13:00:06CDT
0,00
5,00
10,00
15,00
12:58:55 12:59:07 12:59:18 12:59:30 12:59:42 12:59:54 13:00:06
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
16
Diagram2-8Graphicaldepictionofbasicflightdata,12:59:05-13:00:00CDT
-45
-30
-15
0
15
30
4512:59:05
12:59:08
12:59:10
12:59:13
12:59:15
12:59:17
12:59:20
12:59:22
12:59:24
12:59:27
12:59:29
12:59:32
12:59:34
12:59:36
12:59:39
12:59:41
12:59:43
12:59:46
12:59:48
12:59:51
12:59:53
12:59:55
12:59:58
13:00:00
Pitch Roll
0
20
40
60
80
100
12:59:05
12:59:08
12:59:10
12:59:13
12:59:15
12:59:17
12:59:20
12:59:22
12:59:24
12:59:27
12:59:29
12:59:32
12:59:34
12:59:36
12:59:39
12:59:41
12:59:43
12:59:46
12:59:48
12:59:51
12:59:53
12:59:55
12:59:58
13:00:00
Power
0
1
2
12:59:05
12:59:08
12:59:10
12:59:13
12:59:15
12:59:17
12:59:20
12:59:22
12:59:24
12:59:27
12:59:29
12:59:32
12:59:34
12:59:36
12:59:39
12:59:41
12:59:43
12:59:46
12:59:48
12:59:51
12:59:53
12:59:55
12:59:58
13:00:00
Flaps
0
500
1000
1500
12:59:05
12:59:08
12:59:10
12:59:13
12:59:15
12:59:17
12:59:20
12:59:22
12:59:24
12:59:27
12:59:29
12:59:32
12:59:34
12:59:36
12:59:39
12:59:41
12:59:43
12:59:46
12:59:48
12:59:51
12:59:53
12:59:55
12:59:58
13:00:00
AltB HOUelevauon
40,0
90,0
140,0
12:59:05
12:59:08
12:59:10
12:59:13
12:59:15
12:59:17
12:59:20
12:59:22
12:59:24
12:59:27
12:59:29
12:59:32
12:59:34
12:59:36
12:59:39
12:59:41
12:59:43
12:59:46
12:59:48
12:59:51
12:59:53
12:59:55
12:59:58
13:00:00
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
17
Thedetailedanalysisof the flightdataand thegraphicalpresentationsof the flight trackwith the
associated ATC transcript in Figure 2-4 and the graphical presentation of the aircraft’s flight
parameters in Diagrams 2-7 (12:58:55 - 13:00:06 CDT) and 2-8 (12:59:05 - 13:00:00 CDT) for the
continuedpatternmaneuversofN4252Gwereanalysedindetail.
It reveals that between 12:59:22 and 12:59:56 CDT the bank angle was rapidly changing from a
wings-levelflightviaaleftrollof34degreesuptoarightsteepturn4of46degrees.
TheAOPAwebsite (2019) states that flyinga visual pattern shouldbe limited toamaximumbank
angle of 30 degrees (rf. (AOPA.org retrieved from https://www.aopa.org/training-and-
safety/Students/presolo/skills/entering-the-traffic-pattern,2019)).
Thenon-standardphraseology5(“leftheading30degrees”insteadof“turnleftheading030degrees”
or “turn left by 30degrees”) at 12:59:20CDTand runway assignment changes throughATC (from
runway35torunway4andbacktorunway35)withinlessthan1minute(12:58:57CDT–12:59:47
CDT).
4In visual flight turns exceeding 45 degrees of bank are defined as “steep turns” (rf. (US Department ofTransportation,Pilot’sHandbookofAeronauticalKnowledge,2016,G29)).5StandardATCPhraseologiesforVectorstoFinalApproacharedefinedinICAODocument9432(2007),ManualofRadiotelephony,Chapter7.5
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
18
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.12)
Figure2-5Continuedpatternmaneuvers
Diagram2-9Visualdescentangledirecttotheaimingpoint,12:59:54-13:00:54CDT
0,00
1,00
2,00
3,00
4,00
12:59:54 13:00:06 13:00:18 13:00:30 13:00:42 13:00:54
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
19
Diagram2-10Graphicaldepictionofbasicflightdata,12:59:59-13:00:47CDT
-45
-30
-15
0
15
30
4512:59:59
13:00:00
13:00:01
13:00:02
13:00:04
13:00:05
13:00:06
13:00:07
13:00:08
13:00:10
13:00:11
13:00:12
13:00:13
13:00:14
13:00:16
13:00:17
13:00:18
13:00:19
13:00:20
13:00:22
13:00:23
13:00:24
13:00:25
13:00:26
13:00:29
13:00:30
13:00:31
13:00:32
13:00:33
13:00:35
13:00:36
13:00:37
13:00:38
13:00:39
13:00:41
13:00:42
13:00:43
13:00:45
13:00:47
Pitch Roll
0
20
40
60
80
100
12:59:59
13:00:00
13:00:01
13:00:02
13:00:04
13:00:05
13:00:06
13:00:07
13:00:08
13:00:10
13:00:11
13:00:12
13:00:13
13:00:14
13:00:16
13:00:17
13:00:18
13:00:19
13:00:20
13:00:22
13:00:23
13:00:24
13:00:25
13:00:26
13:00:29
13:00:30
13:00:31
13:00:32
13:00:33
13:00:35
13:00:36
13:00:37
13:00:38
13:00:39
13:00:41
13:00:42
13:00:43
13:00:45
13:00:47
Power
0
1
2
12:59:59
13:00:00
13:00:01
13:00:02
13:00:04
13:00:05
13:00:06
13:00:07
13:00:08
13:00:10
13:00:11
13:00:12
13:00:13
13:00:14
13:00:16
13:00:17
13:00:18
13:00:19
13:00:20
13:00:22
13:00:23
13:00:24
13:00:25
13:00:26
13:00:29
13:00:30
13:00:31
13:00:32
13:00:33
13:00:35
13:00:36
13:00:37
13:00:38
13:00:39
13:00:41
13:00:42
13:00:43
13:00:45
13:00:47
Flaps
0
500
1000
1500
12:59:59
13:00:00
13:00:01
13:00:02
13:00:04
13:00:05
13:00:06
13:00:07
13:00:08
13:00:10
13:00:11
13:00:12
13:00:13
13:00:14
13:00:16
13:00:17
13:00:18
13:00:19
13:00:20
13:00:22
13:00:23
13:00:24
13:00:25
13:00:26
13:00:29
13:00:30
13:00:31
13:00:32
13:00:33
13:00:35
13:00:36
13:00:37
13:00:38
13:00:39
13:00:41
13:00:42
13:00:43
13:00:45
13:00:47
AltB HOUelevauon
40,0
90,0
140,0
12:59:59
13:00:00
13:00:01
13:00:02
13:00:04
13:00:05
13:00:06
13:00:07
13:00:08
13:00:10
13:00:11
13:00:12
13:00:13
13:00:14
13:00:16
13:00:17
13:00:18
13:00:19
13:00:20
13:00:22
13:00:23
13:00:24
13:00:25
13:00:26
13:00:29
13:00:30
13:00:31
13:00:32
13:00:33
13:00:35
13:00:36
13:00:37
13:00:38
13:00:39
13:00:41
13:00:42
13:00:43
13:00:45
13:00:47
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
20
Thedetailedanalysisof the flightdataand thegraphicalpresentationsof the flight trackwith the
associated ATC transcript in Figure 2-5 and the graphical presentation of the aircraft’s flight
parameters inDiagrams 2-9 (12:59:54 - 13:00:54 CDT) and 2-10 (12:59:59 - 13:00:47 CDT) for the
continuedpatternmaneuversofN4252Gwereanalysedindetail.
Itrevealsthatat13:00:14CDTtheATCwasuncertaininwhichdirectionN4252Gwasturning.After
clarificationthepilotwasclearedbyATCforatightturn(“keepittight,Ineedyoutomakeittight”),
whichisanon-standardICAOphraseology.Thefollowingbankanglewasincreasedtoamaximumof
50degreesat13:00:30CDT,whichreducedthestallspeedmargin6to15kts.
At13:00:42, theaircraftwasataposition (altitude998 ft,direct visualdescentangle2.92°, speed
107 KIAS, approximately7 15 degrees left of centerline) suitable for landing at runway 35. For an
unknownreason,thepilotadvisedATCaboutheruncertaintyofbeingcorrectlylinedupforrunway
35, most probably due a severe degradation of situational awareness due to the high workload
situation. At 13:00:47 CDT, ATC cleared the pilot to turn right (without any heading assignment,
whichisnotincompliancewithICAOstandardphraseology)andaclimbto1600ft8.
6asdifferencebetweenIASandVsin[kts]7measuredbytheauthorwithGoogleEarthProApplication,consideringtheN4252GRadarTargetFile-HOUASR Google Earth KML Target File as retrieved from NTSB DMS Website:https://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=60618&CFID=2395938&CFTOKEN=81732fd00bba5423-5AB1BC7B-CB39-E91F-3732EB517FD2FBDB8Author’snote:ATCclearancetoclimbto1600ftaboveMSL(consideringHOUairportelevationof43ftaboveMSL)seemsunusualhighforexpectingtokeepasingleengineaircraftvisuallyinanairport’strafficpattern.
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
21
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.13)
Figure2-6Changingapproachfromrunway4torunway35
Diagram2-11Visualdescentangledirecttotheaimingpoint,13:00:42-13:01:42CDT
0,00
2,00
4,00
6,00
8,00
10,00
12,00
13:00:42 13:00:54 13:01:06 13:01:18 13:01:30 13:01:42
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
22
Diagram2-12Graphicaldepictionofbasicflightdata,13:00:47-13:01:52CDT
-45
-30
-15
0
15
30
4513:00:47
13:00:49
13:00:51
13:00:54
13:00:56
13:00:59
13:01:01
13:01:05
13:01:07
13:01:11
13:01:13
13:01:16
13:01:19
13:01:21
13:01:24
13:01:26
13:01:28
13:01:31
13:01:33
13:01:36
13:01:38
13:01:40
13:01:43
13:01:45
13:01:48
13:01:50
13:01:52
Pitch Roll
0
20
40
60
80
100
13:00:47
13:00:49
13:00:51
13:00:54
13:00:56
13:00:59
13:01:01
13:01:05
13:01:07
13:01:11
13:01:13
13:01:16
13:01:19
13:01:21
13:01:24
13:01:26
13:01:28
13:01:31
13:01:33
13:01:36
13:01:38
13:01:40
13:01:43
13:01:45
13:01:48
13:01:50
13:01:52
Power
0
1
2
13:00:47
13:00:49
13:00:51
13:00:54
13:00:56
13:00:59
13:01:01
13:01:05
13:01:07
13:01:11
13:01:13
13:01:16
13:01:19
13:01:21
13:01:24
13:01:26
13:01:28
13:01:31
13:01:33
13:01:36
13:01:38
13:01:40
13:01:43
13:01:45
13:01:48
13:01:50
13:01:52
Flaps
0
500
1000
1500
13:00:47
13:00:49
13:00:51
13:00:54
13:00:56
13:00:59
13:01:01
13:01:05
13:01:07
13:01:11
13:01:13
13:01:16
13:01:19
13:01:21
13:01:24
13:01:26
13:01:28
13:01:31
13:01:33
13:01:36
13:01:38
13:01:40
13:01:43
13:01:45
13:01:48
13:01:50
13:01:52
AltB HOUelevauon
40,0
90,0
140,0
13:00:47
13:00:49
13:00:51
13:00:54
13:00:56
13:00:59
13:01:01
13:01:05
13:01:07
13:01:11
13:01:13
13:01:16
13:01:19
13:01:21
13:01:24
13:01:26
13:01:28
13:01:31
13:01:33
13:01:36
13:01:38
13:01:40
13:01:43
13:01:45
13:01:48
13:01:50
13:01:52
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
23
Thedetailedanalysisof the flightdataand thegraphicalpresentationsof the flight trackwith the
associated ATC transcript in Figure 2-6 and the graphical presentation of the aircraft’s flight
parameters inDiagrams2-11 (13:00:42 -13:01:42CDT)and2-12 (13:00:47 -13:01:52CDT) for the
patternmaneuversofN4252Gwhentheapproachwaschangedfromrunway4torunway35were
analysedindetail.
Itrevealsthatforthediscontinuedapproachthepowerwasincreasedfrom53%to82%at13:00:57
CDT. As the flapswere not extended themissed approach procedurewas performedwithout the
requirement to retract the flaps. The airspeed at the time of themissed approachwas 114 KIAS.
From13:01:33CDTtill13:01:37CDTthebankanglewasexceeding40degrees.At13:01:29CDTATC
advisedtomakearightturn“all thewayaround”torunway35,whilethepilotwas increasingthe
bankangleupto42degrees(at13:01:33CDT)inarightturn.At13:01:42CDTtheaircraftwasona
visualdescentangletotheaimingpointofrunway35of10.9degrees(notethatthePAPIforrunway
35wascalibrated for3.0degrees) ina rightbanking turnof32degrees.At13:01:46CDTthepilot
selectedtheflapsto50%withaspeedof117KIAS(2ktsbelowVfe)inarightturnwithabankangle
of25degrees.
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
24
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.14)
Figure2-7Settingupforinitialstraight-inapproachtorunway35
Diagram2-13Visualdescentangledirecttotheaimingpoint,13:01:42-13:02:54CDT
0,00
5,00
10,00
15,00
13:01:42 13:01:54 13:02:06 13:02:18 13:02:30 13:02:42 13:02:54
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
25
Diagram2-14Graphicaldepictionofbasicflightdata,13:01:52-13:02:52CDT
-45
-30
-15
0
15
30
4513:01:52
13:01:55
13:01:57
13:02:00
13:02:02
13:02:04
13:02:07
13:02:09
13:02:12
13:02:14
13:02:17
13:02:19
13:02:21
13:02:24
13:02:26
13:02:30
13:02:32
13:02:35
13:02:37
13:02:39
13:02:42
13:02:44
13:02:47
13:02:49
13:02:52
Pitch Roll
0
20
40
60
80
100
13:01:52
13:01:55
13:01:57
13:02:00
13:02:02
13:02:04
13:02:07
13:02:09
13:02:12
13:02:14
13:02:17
13:02:19
13:02:21
13:02:24
13:02:26
13:02:30
13:02:32
13:02:35
13:02:37
13:02:39
13:02:42
13:02:44
13:02:47
13:02:49
13:02:52
Power
0
1
2
13:01:52
13:01:55
13:01:57
13:02:00
13:02:02
13:02:04
13:02:07
13:02:09
13:02:12
13:02:14
13:02:17
13:02:19
13:02:21
13:02:24
13:02:26
13:02:30
13:02:32
13:02:35
13:02:37
13:02:39
13:02:42
13:02:44
13:02:47
13:02:49
13:02:52
Flaps
0
500
1000
1500
13:01:52
13:01:55
13:01:57
13:02:00
13:02:02
13:02:04
13:02:07
13:02:09
13:02:12
13:02:14
13:02:17
13:02:19
13:02:21
13:02:24
13:02:26
13:02:30
13:02:32
13:02:35
13:02:37
13:02:39
13:02:42
13:02:44
13:02:47
13:02:49
13:02:52
AltB HOUelevauon
40,0
60,0
80,0
100,0
120,0
13:01:52
13:01:55
13:01:57
13:02:00
13:02:02
13:02:04
13:02:07
13:02:09
13:02:12
13:02:14
13:02:17
13:02:19
13:02:21
13:02:24
13:02:26
13:02:30
13:02:32
13:02:35
13:02:37
13:02:39
13:02:42
13:02:44
13:02:47
13:02:49
13:02:52
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
26
TheflightdataandthegraphicalpresentationsoftheflighttrackwiththeassociatedATCtranscript
in Figure 2-7 and the graphical presentation of the aircraft’s flight parameters in Diagrams 2-13
(13:01:42-13:02:54CDT)and2-14(13:01:52-13:02:52CDT)forthesetupofN4252Gfortheinitial
straight-inapproachtorunway35wereanalysedindetail.
At13:02:00CDT, theATCadvised thepilot “lookinggood to start thedescent to runway35”. The
aircraftwasatapositionwith5.7degreesvisualdescentangletorunway35,atanaltitudeAltBof
1117ftwith95KIAS,stillclimbingwitha35degreesbankangle.
At13:02:12CDT,whenthepilotreportedtherunwayinsighttheaircraftwasatapositionwith6.0
degreesvisualdescentangletorunway35(notethatthePAPIforrunway35wascalibratedfor3.0
degrees),withanairspeedof82.4KIAS,turningrightinasteepturnof46degreesofbankangle.The
highbankanglereducedthestallspeedmarginto4kts.Therefore,itcanbeassumedthatthestall
warningwastriggered9.Thepilotsubsequentlyreducedtheangleofpitchandrollandthestallspeed
marginincreased.At13:02:15CDT,theflapswereextendedto100%whilstturningrightwithabank
angleof37degrees.
At13:02:24CDT,thepowerwasreducedtoidlewithin5seconds.Simultaneously,ATCadvisedthe
landingclearanceandtheactualwindof100degreesat15ktswithgusts to20kts forrunway35.
AccordingtotheCirrusEnvelopeofSafety(refertoLAppendix,Figure6-3EnvelopeofSafety),the
reportedwindwas exceeding10 the personalized x-wind limit (wind limit 15kts, x-wind limit 5kts,
maximumgust5kts)accordingtothePilot’sCapabilityCategory(fordetails,refertoDAppendix).
At 13:02:29, the pilot advised to ATC “trying to lose altitude”. The initiated descent rate for a
stabilizedapproachtotheaimingpointofrunway35wasnotsufficientandthevisualdescentangle
further increased.At13:02:54,CDTthevisualdescentangle to theaimingpointof runway35was
12.0degrees,farabovethenominalPAPIangleof3.0degrees.
9“thestallspeedwarninghornsound[s]between5and10ktsbeforethestall”(POH-SR20,2015,p.4-23).FortheprevailinganalysistheauthorhasanticipatedthatstallwarningtriggersifIAS<(Vs+5kts).10TheauthorofthisthesisrecalculatedthewindcomponentsconsideringFigure6-4Windcomponentdiagramasfollows:100°/15ktssteady(gustsupto20kts)equals4kts(gustsupto5kts)tailwindand15kts(gustsupto19kts)crosswindforrunway35(356°runwaytrack).
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
27
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.15)
Figure2-8Runway35firstapproachandgo-around
Diagram2-15Visualdescentangledirecttotheaimingpoint,13:02:54-13:04:07CDT
0,00
5,00
10,00
15,00
20,00
25,00
30,00
13:02:54 13:03:07 13:03:19 13:03:31 13:03:43 13:03:55 13:04:07
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
28
Diagram2-16Graphicaldepictionofbasicflightdata,13:02:53-13:03:57CDT
-45
-30
-15
0
15
30
4513:02:53
13:02:55
13:02:58
13:03:00
13:03:02
13:03:05
13:03:07
13:03:10
13:03:12
13:03:15
13:03:17
13:03:19
13:03:22
13:03:24
13:03:27
13:03:29
13:03:32
13:03:34
13:03:36
13:03:39
13:03:41
13:03:44
13:03:46
13:03:50
13:03:52
13:03:55
13:03:57
Pitch Roll
0
20
40
60
80
100
13:02:53
13:02:55
13:02:58
13:03:00
13:03:02
13:03:05
13:03:07
13:03:10
13:03:12
13:03:15
13:03:17
13:03:19
13:03:22
13:03:24
13:03:27
13:03:29
13:03:32
13:03:34
13:03:36
13:03:39
13:03:41
13:03:44
13:03:46
13:03:50
13:03:52
13:03:55
13:03:57
Power
0
1
2
13:02:53
13:02:55
13:02:58
13:03:00
13:03:02
13:03:05
13:03:07
13:03:10
13:03:12
13:03:15
13:03:17
13:03:19
13:03:22
13:03:24
13:03:27
13:03:29
13:03:32
13:03:34
13:03:36
13:03:39
13:03:41
13:03:44
13:03:46
13:03:50
13:03:52
13:03:55
13:03:57
Flaps
0
500
1000
1500
13:02:53
13:02:55
13:02:58
13:03:00
13:03:02
13:03:05
13:03:07
13:03:10
13:03:12
13:03:15
13:03:17
13:03:19
13:03:22
13:03:24
13:03:27
13:03:29
13:03:32
13:03:34
13:03:36
13:03:39
13:03:41
13:03:44
13:03:46
13:03:50
13:03:52
13:03:55
13:03:57
AltB HOUelevauon
40,0
60,0
80,0
100,0
13:02:53
13:02:55
13:02:58
13:03:00
13:03:02
13:03:05
13:03:07
13:03:10
13:03:12
13:03:15
13:03:17
13:03:19
13:03:22
13:03:24
13:03:27
13:03:29
13:03:32
13:03:34
13:03:36
13:03:39
13:03:41
13:03:44
13:03:46
13:03:50
13:03:52
13:03:55
13:03:57
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
29
TheflightdataandthegraphicalpresentationsoftheflighttrackwiththeassociatedATCtranscript
in Figure 2-8 and the graphical presentation of the aircraft’s flight parameters in Diagrams 2-15
(13:02:54-13:04:07CDT)and2-16(13:02:53-13:03:57CDT)forthefirstapproachandgo-aroundof
N4252Gtorunway35wereanalysedindetail.
At 13:03:29 CDT, when the aiming point of runway 35 was already overflown and the pilot still
seemedtointendtolandonrunway35,ATCadvisedthepilotabouttheaircraft’shighposition(“you
might be too high”). The pilot initiated a go-around at 13:03:34 CDT. The power was not set to
maximumpower(forproceduraldetails,refertoEAppendix).Theairspeedwasat64.1KIAS,when
theflapswereretractedto50%at13:03:36CDT.Thestallspeedmargindecreasedto2ktswithan
activestallwarning11.ATCadvisedat13:03:43CDTthatthepilotshouldexpectarighttrafficpattern
forrunway35.
At13:03:46CDT,atanaltitudeof192fttheflapswereretractedto0%at68.7KIAS(wellbelowthe
recommendedspeedof83KIAS)withastallspeedmarginof4ktsandthepowersetto77%instead
ofmaximumpower (forproceduraldetails, refer toEAppendix). Thepitchanglewasnot reduced
and the speed furtherdecreaseduntil reaching the stall speedat13:03:49CDT.Subsequently, the
pitchanglewasslightlyreducedandtheaircraftleftthespeedregimetriggeringastallwarningatan
altitudeof183ftat13:03:56CDTwithapositivespeedtrend.
11“thestallspeedwarninghornsound[s]between5and10ktsbeforethestall”(POH-SR20,2015,p.4-23).FortheprevailinganalysistheauthorhasanticipatedthatstallwarningtriggersifIAS<(Vs+5kts).
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
30
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.16)
Figure2-9Preparingforsecondapproachtorunway35
Diagram2-17Visualdescentangledirecttotheaimingpoint,13:03:55-13:05:55CDT
0,00
5,00
10,00
15,00
20,00
25,00
13:03:55 13:04:07 13:04:19 13:04:31 13:04:43 13:04:55 13:05:07 13:05:19 13:05:31 13:05:43 13:05:55
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
31
Diagram2-18Graphicaldepictionofbasicflightdata,13:03:56-13:05:50CDT
-45
-30
-15
0
15
30
4513:03:56
13:04:01
13:04:04
13:04:08
13:04:13
13:04:18
13:04:21
13:04:25
13:04:29
13:04:32
13:04:36
13:04:40
13:04:43
13:04:47
13:04:51
13:04:54
13:04:58
13:05:02
13:05:05
13:05:09
13:05:13
13:05:16
13:05:20
13:05:24
13:05:27
13:05:32
13:05:36
13:05:39
13:05:43
13:05:47
13:05:50
Pitch Roll
0
20
40
60
80
100
13:03:56
13:04:01
13:04:04
13:04:08
13:04:13
13:04:18
13:04:21
13:04:25
13:04:29
13:04:32
13:04:36
13:04:40
13:04:43
13:04:47
13:04:51
13:04:54
13:04:58
13:05:02
13:05:05
13:05:09
13:05:13
13:05:16
13:05:20
13:05:24
13:05:27
13:05:32
13:05:36
13:05:39
13:05:43
13:05:47
13:05:50
Power
0
1
2
13:03:56
13:04:01
13:04:04
13:04:08
13:04:13
13:04:18
13:04:21
13:04:25
13:04:29
13:04:32
13:04:36
13:04:40
13:04:43
13:04:47
13:04:51
13:04:54
13:04:58
13:05:02
13:05:05
13:05:09
13:05:13
13:05:16
13:05:20
13:05:24
13:05:27
13:05:32
13:05:36
13:05:39
13:05:43
13:05:47
13:05:50
Flaps
0
500
1000
1500
13:03:56
13:04:01
13:04:04
13:04:08
13:04:13
13:04:18
13:04:21
13:04:25
13:04:29
13:04:32
13:04:36
13:04:40
13:04:43
13:04:47
13:04:51
13:04:54
13:04:58
13:05:02
13:05:05
13:05:09
13:05:13
13:05:16
13:05:20
13:05:24
13:05:27
13:05:32
13:05:36
13:05:39
13:05:43
13:05:47
13:05:50
AltB HOUelevauon
40,0
60,0
80,0
100,0
120,0
13:03:56
13:04:01
13:04:04
13:04:08
13:04:13
13:04:18
13:04:21
13:04:25
13:04:29
13:04:32
13:04:36
13:04:40
13:04:43
13:04:47
13:04:51
13:04:54
13:04:58
13:05:02
13:05:05
13:05:09
13:05:13
13:05:16
13:05:20
13:05:24
13:05:27
13:05:32
13:05:36
13:05:39
13:05:43
13:05:47
13:05:50
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
32
TheflightdataandthegraphicalpresentationsoftheflighttrackwiththeassociatedATCtranscript
in Figure 2-9 and the graphical presentation of the aircraft’s flight parameters in Diagrams 2-17
(13:03:55 - 13:05:55 CDT) and 2-18 (13:03:56 - 13:05:50 CDT) whilst preparing for the second
approachofN4252Gtorunway35wereanalysedindetail.At13:04:39CDTtheATCadvisedtoenter
the right downwind for runway 35. As there was no other traffic reported for runway 4 by ATC,
properapplicationofriskassessmenthadresultedinrequestingrunway4toimprovetheprevailing
windconditionsforapproachandlanding.
At13:04:27,whilstina29degreebankedrightturnwithaspeedof74KIASthestallspeedmargin
was reduced to 4kts. Therefore, it can be assumed that the stall warning was triggered12 for 4
seconds.
12“thestallspeedwarninghornsound[s]between5and10ktsbeforethestall”(POH-SR20,2015,p.4-23).FortheprevailinganalysistheauthorhasanticipatedthatstallwarningtriggersifIAS<(Vs+5kts).
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
33
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.17)
Figure2-10Downwindtofinalturn,secondapproachtorunway35
Diagram2-19Visualdescentangledirecttotheaimingpoint,13:05:43-13:07:06CDT
0,00
5,00
10,00
15,00
20,00
25,00
13:05:43 13:05:55 13:06:06 13:06:18 13:06:30 13:06:42 13:06:54 13:07:06
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
34
Diagram2-20Graphicaldepictionofbasicflightdata,13:05:50-13:07:00CDT
-45
-30
-15
0
15
30
4513:05:50
13:05:53
13:05:55
13:05:58
13:06:00
13:06:03
13:06:05
13:06:08
13:06:10
13:06:13
13:06:15
13:06:17
13:06:20
13:06:24
13:06:26
13:06:28
13:06:31
13:06:33
13:06:36
13:06:38
13:06:41
13:06:43
13:06:46
13:06:48
13:06:51
13:06:53
13:06:55
13:06:58
13:07:00
Pitch Roll
0
20
40
60
80
100
13:05:50
13:05:53
13:05:55
13:05:58
13:06:00
13:06:03
13:06:05
13:06:08
13:06:10
13:06:13
13:06:15
13:06:17
13:06:20
13:06:24
13:06:26
13:06:28
13:06:31
13:06:33
13:06:36
13:06:38
13:06:41
13:06:43
13:06:46
13:06:48
13:06:51
13:06:53
13:06:55
13:06:58
13:07:00
Power
0
1
2
13:05:50
13:05:53
13:05:55
13:05:58
13:06:00
13:06:03
13:06:05
13:06:08
13:06:10
13:06:13
13:06:15
13:06:17
13:06:20
13:06:24
13:06:26
13:06:28
13:06:31
13:06:33
13:06:36
13:06:38
13:06:41
13:06:43
13:06:46
13:06:48
13:06:51
13:06:53
13:06:55
13:06:58
13:07:00
Flaps
0
500
1000
1500
13:05:50
13:05:53
13:05:55
13:05:58
13:06:00
13:06:03
13:06:05
13:06:08
13:06:10
13:06:13
13:06:15
13:06:17
13:06:20
13:06:24
13:06:26
13:06:28
13:06:31
13:06:33
13:06:36
13:06:38
13:06:41
13:06:43
13:06:46
13:06:48
13:06:51
13:06:53
13:06:55
13:06:58
13:07:00
AltB HOUelevauon
40,0
60,0
80,0
100,0
120,0
13:05:50
13:05:53
13:05:55
13:05:58
13:06:00
13:06:03
13:06:05
13:06:08
13:06:10
13:06:13
13:06:15
13:06:17
13:06:20
13:06:24
13:06:26
13:06:28
13:06:31
13:06:33
13:06:36
13:06:38
13:06:41
13:06:43
13:06:46
13:06:48
13:06:51
13:06:53
13:06:55
13:06:58
13:07:00
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
35
TheflightdataandthegraphicalpresentationsoftheflighttrackwiththeassociatedATCtranscript
in Figure 2-10 and the graphical presentation of the aircraft’s flight parameters in Diagram 2-19
(13:05:43-13:07:06CDT)and2-20(13:05:50-13:07:00CDT)whilstproceedingondownwindandto
the final turn for the secondapproach to runway35ofN4252Gwereanalysed indetail. Between
13:06:42and13:06:53CDT,whenturningonfinalforrunway35thebankanglewasincreasedupto
amaximumof51degrees.At13:06:55CDT,theflapswereextendedto50%andthepowerreduced
to idle,whilst the visual descent anglewas at 5.7 degrees (note that the PAPI for runway 35was
calibratedfor3.0degrees)with101.3KIASina31degreesofbankangleturn.
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
36
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.18)
Figure2-11Secondapproachtorunway35
Diagram2-21Visualdescentangledirecttotheaimingpoint,13:06:54-13:08:07CDT
0,00
5,00
10,00
15,00
20,00
25,00
30,00
13:06:54 13:07:06 13:07:18 13:07:30 13:07:43 13:07:55 13:08:07
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
37
Diagram2-22Graphicaldepictionofbasicflightdata,13:06:59-13:07:59CDT
-45
-30
-15
0
15
30
4513:06:59
13:07:02
13:07:04
13:07:08
13:07:10
13:07:13
13:07:15
13:07:17
13:07:20
13:07:22
13:07:25
13:07:27
13:07:30
13:07:32
13:07:35
13:07:37
13:07:40
13:07:42
13:07:45
13:07:47
13:07:49
13:07:52
13:07:54
13:07:57
13:07:59
Pitch Roll
0
20
40
60
80
100
13:06:59
13:07:02
13:07:04
13:07:08
13:07:10
13:07:13
13:07:15
13:07:17
13:07:20
13:07:22
13:07:25
13:07:27
13:07:30
13:07:32
13:07:35
13:07:37
13:07:40
13:07:42
13:07:45
13:07:47
13:07:49
13:07:52
13:07:54
13:07:57
13:07:59
Power
0
1
2
13:06:59
13:07:02
13:07:04
13:07:08
13:07:10
13:07:13
13:07:15
13:07:17
13:07:20
13:07:22
13:07:25
13:07:27
13:07:30
13:07:32
13:07:35
13:07:37
13:07:40
13:07:42
13:07:45
13:07:47
13:07:49
13:07:52
13:07:54
13:07:57
13:07:59
Flaps
0
500
1000
1500
13:06:59
13:07:02
13:07:04
13:07:08
13:07:10
13:07:13
13:07:15
13:07:17
13:07:20
13:07:22
13:07:25
13:07:27
13:07:30
13:07:32
13:07:35
13:07:37
13:07:40
13:07:42
13:07:45
13:07:47
13:07:49
13:07:52
13:07:54
13:07:57
13:07:59
AltB HOUelevauon
40,0
60,0
80,0
100,0
120,0
13:06:59
13:07:02
13:07:04
13:07:08
13:07:10
13:07:13
13:07:15
13:07:17
13:07:20
13:07:22
13:07:25
13:07:27
13:07:30
13:07:32
13:07:35
13:07:37
13:07:40
13:07:42
13:07:45
13:07:47
13:07:49
13:07:52
13:07:54
13:07:57
13:07:59
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
38
TheflightdataandthegraphicalpresentationsoftheflighttrackwiththeassociatedATCtranscript
in Figure 2-11 and the graphical presentation of the aircraft’s flight parameters in Diagrams 2-21
(13:06:54-13:08:07CDT)and2-22(13:06:59-13:07:59CDT)whilstperformingthesecondapproach
torunway35ofN4252Gwereanalysedindetail.
The power was set to idle at 13:07:02 CDT. At 13:07:05 CDT, the pilot of N4252G reported the
runway insight toATC.At13:07:10CDTATCadvised the landingclearanceandtheactualwindof
090degreesat13ktswithguststo18ktsforrunway35.AccordingtotheCirrusEnvelopeofSafety
(refer to L Appendix, Figure 6-3 Envelope of Safety), the reported wind was exceeding13 the
personalizedx-windlimit(windlimit15kts,x-windlimit5kts,maximumgust5kts)accordingtothe
Pilot’sCapabilityCategory(fordetails,refertoDAppendix).
At13:07:18CDT,beforetheflapsweresetto100%thevisualdescentanglewas7.7degreeswithan
increasingtrend(notethatthePAPIforrunway35wascalibratedfor3.0degrees).Whenthepilotof
N4252Greadbackthelandingclearanceforrunway35andadvised“tryingtogetdownagain”,the
flaps were simultaneously extended from 50% to 100%, whilst the speedwas at 94.8 KIAS. From
13:07:32until13:07:42CDTthespeedwasdecreasingbelow78KIAS(downtoaminimumof72KIAS
at 13:07:38 CDT), which is the recommended approach speed (for procedural details refer to E
Appendix)forthe100%flapsconfiguration.
13TheauthorofthisthesisrecalculatedthewindcomponentsconsideringFigure6-4Windcomponentdiagramasfollows:090°/13ktssteady(withgustsupto18kts)equals1kt(nogusts)tailwindand13kts(gustsupto18kts)crosswindforrunway35(356°runwaytrack).
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
39
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.19)
Figure2-12Go-aroundfollowingsecondapproachtorunway35andlossofcontact
Diagram2-23Visualdescentangledirecttotheaimingpoint,13:07:55-13:09:07CDT
0,00
5,00
10,00
15,00
20,00
25,00
13:07:55 13:08:07 13:08:19 13:08:31 13:08:43 13:08:55 13:09:07
Ry4-Path Ry35-Path
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
40
Diagram2-24Graphicaldepictionofbasicflightdata,13:08:00-13:09:02CDT
-75
-60
-45
-30
-15
0
1513:08:00
13:08:03
13:08:05
13:08:09
13:08:12
13:08:14
13:08:16
13:08:19
13:08:21
13:08:24
13:08:26
13:08:29
13:08:31
13:08:35
13:08:37
13:08:40
13:08:42
13:08:45
13:08:47
13:08:50
13:08:52
13:08:55
13:08:57
13:09:00
13:09:02
Pitch Roll
0
20
40
60
80
100
13:08:00
13:08:03
13:08:05
13:08:09
13:08:12
13:08:14
13:08:16
13:08:19
13:08:21
13:08:24
13:08:26
13:08:29
13:08:31
13:08:35
13:08:37
13:08:40
13:08:42
13:08:45
13:08:47
13:08:50
13:08:52
13:08:55
13:08:57
13:09:00
13:09:02
Power
0
1
2
13:08:00
13:08:03
13:08:05
13:08:09
13:08:12
13:08:14
13:08:16
13:08:19
13:08:21
13:08:24
13:08:26
13:08:29
13:08:31
13:08:35
13:08:37
13:08:40
13:08:42
13:08:45
13:08:47
13:08:50
13:08:52
13:08:55
13:08:57
13:09:00
13:09:02
Flaps
0
500
1000
1500
13:08:00
13:08:03
13:08:05
13:08:09
13:08:12
13:08:14
13:08:16
13:08:19
13:08:21
13:08:24
13:08:26
13:08:29
13:08:31
13:08:35
13:08:37
13:08:40
13:08:42
13:08:45
13:08:47
13:08:50
13:08:52
13:08:55
13:08:57
13:09:00
13:09:02
AltB HOUelevauon
40,0
60,0
80,0
100,0
120,0
13:08:00
13:08:03
13:08:05
13:08:09
13:08:12
13:08:14
13:08:16
13:08:19
13:08:21
13:08:24
13:08:26
13:08:29
13:08:31
13:08:35
13:08:37
13:08:40
13:08:42
13:08:45
13:08:47
13:08:50
13:08:52
13:08:55
13:08:57
13:09:00
13:09:02
IAS Vs Vfe/Vno
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
41
TheflightdataandthegraphicalpresentationsoftheflighttrackwiththeassociatedATCtranscript
in Figure 2-12 and the graphical presentation of the aircraft’s flight parameters in Diagrams 2-23
(13:07:55-13:09:07CDT)and2-24(13:08:00-13:09:02CDT)whilstperformingthesecondapproach
torunway35ofN4252Gwereanalysedindetail.
Thepilotcontinuedthefinalapproachtorunway35.At13:08:19CDTatapositioninthelastthirdof
runway35(refertoFigure2-12)atanaltitudeof107ft(64ftaboveground)andataspeedof66.7
KIAS(notethattherecommendedapproachspeedwithflaps100%is78KIAS;forproceduraldetails,
refertoEAppendix)thego-aroundwasinitiated.Thepowerwassetto96%.Theairspeedatthetime
ofgo-aroundwas66.4KIAS.Theflapswerenotretractedandleftat100%.
At13:08:45CDT,thealtitudewasat374ftwhilstperformingaslightleftbankedturn.Thestallspeed
marginreached5ktsand itcanbeassumedthatthestallwarningwastriggered14.Thepitchangle
wasnotreduced.At13:08:53CDT,withastallspeedmarginof2ktsthepowerwasreducedto78%.
At13:08:55CDT,atanaltitudeof463ftwith62.4KIASandastallspeedmarginof1kttheflapswere
retractedto50%.Althoughtheindicatedairspeedwasalreadybelowthecalculatedstallspeedand
thepitchanglewasnotreduced,thepilotcontinuedtofly inaslight leftturnwithabankangleof
approximately 20 degrees. The turn increased the tailwind component and further lowered the
energystateoftheaircraft.
At13:09:02CDT,withapitchangleof9degrees,ina26degreesbankedleftturn,thepowersetto
84%,at58.4KIAS(14.6ktsbelowthecalculatedstallspeed),atanaltitudeof496fttheflapswere
retractedto0%.Subsequently,thecontroloftheaircraftwaslost.
Thelastdatareadoutbeforetheimpactat13:09:03CDTindicatedaleftbankangleof71degrees.
14“thestallspeedwarninghornsound[s]between5and10ktsbeforethestall”(POH-SR20,2015,p.4-23).FortheprevailinganalysistheauthorhasanticipatedthatstallwarningtriggersifIAS<(Vs+5kts).
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
42
2.3 GeneralDefinitionsforthePresentCASTAnalysis
ReferringtoLeveson(2018),distinguishingbetweenhazardsandlossesisrequired,giventhatlosses
may involve aspects of the environment overwhich the system controllers or operators have only
partialcontrolornocontrolatall(rf.(Leveson,STPAHandbook,2018,p.17)).
FortheprevailingSTAMP(Leveson,2011)modelingoftheN4252Gaccidenttheauthorofthisthesis
has specified in the following the Loss [L], the involvedHazards [H] and the associatedHigh-Level
SafetyConstraints[HLSC]:
[L] Thelossoflifeorinjurytopeopleasaresultofapilot’slossofaircraftcontrolinflightwhilst
intendingtolandatechnologically-advancedaircraft(TAA)inabusyairportenvironment.
Thefollowinghazards[H]describesystemstatesorconditionsthatleadtotheabove-definedlossof
aircraftcontrolinaworst-casescenario:
[H-1] Aircraftapprovedenvelopeofflightisexceeded.
[H-2] “Aircraftairframeintegrityislost”(Leveson,STPAHandbook,2018,p.20).
[H-3] Regaininglostaircraftcontrolinflightisnotachievedbeforeasafegroundcontact.
[H-4] Aircraftisuncontrolled.
[H-5] CAPSisnotdeployedinalife-threateningemergency.
[H-6] Biennialflightreviewisexceeded.
[H-7] Pilot’sworkloadexceedssafelymanageablecapabilitiesanddegradesSA.
[H-8] ATCClearancesarecomplexandchangedunpredictablywithinashorttimeframe.
[H-9] Thefinalapproachiscontinuedwithoutmeetingstabilizedapproachcriteria.
ReferringtoNancyLeveson’sdefinitionofhazardinAAppendix,itseemsobviousthatenvironmental
conditionscanaffectacontroller’sprocessmodel, inso far that inaworst-casescenarioallof the
unsafecontrolactionsinitiatedbytheindividualcomponentsinteracttogethersuchthattheresultis
a loss (accident). Therefore, respective safety constraints need to be put in place tomitigate the
encounterofunsafecontrolactionsandtheinteractionsofthecomponentsasawhole.
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
43
The high-level safety constraints [HLSC] and requirements associated with each of the afore-
mentionedhazardsaredefinedasfollows:
[HLSC-1] If an aircraft exceeds the approved envelope of flight, then the exceedance must be
detectedandmeasurestakentoavoidapilot’slossofaircraftcontrol(rf.(Leveson,STPA
Handbook,2018,p.20)).
[HLSC-2] “Aircraftairframeintegritymustbemaintainedunderworst-caseconditions”(Leveson,
STPAHandbook,2018,p.20).
[HLSC-3] If regaining lost aircraft control in flight cannot be expected before a safe ground
contact, then measures shall be taken on time to minimize loss-of-life or injury to
people.
[HLSC-4] Aircraftcontrolmustbemaintainedunderallconditions.
[HLSC-5] IfCAPSisnotdeployedinalife-threateningemergency,thenalternativemeasuresmust
beperformed.
[HLSC-6] If thebiennial flight review is exceeded, thenmeasuresmustbeenforced toprohibit
exercisingprivilegesaspilotincommand.
[HLSC-7] If the pilot’s workload exceeds its safely manageable capabilities, then measures to
regainasafelevelofworkloadmustbeperformed.
[HLSC-8] IftrafficsituationsrequirerevisedATCstrategiesonshortnotice,thenmeasuresmust
beenforcedtoenableaclearunderstandingforallinvolvedparties.
[HLSC-9] Ifthestabilizedapproachcriteriaarenotmetanimmediategoaroundshallbeinitiated.
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
44
2.4 GeneralModelofHierarchicalControlStructure
FormodelingtheaccidentofN4252G’soperationpriortoitsfinalgroundimpactinSTAMP(Leveson,
2011), a hierarchical control structure was developed by the author, refer to Figure 2-13. It
supported the determination and understanding of the process how higher levels in the control
structure contributed to unsafe control actions by considering available information, feedbacks,
physicalflowsandenvironmentalconditions(rf.(Leveson,EngineeringaSaferWorld,2011,p.351)).
Thefollowingcodingsareapplied:
• rectanglesrepresentindividualcontrollers;
• continuouslinesrepresentcontrolactions;
• dashedlinesindicateinformation,feedbacks,orphysicalflows;
• oversizedarrowsymbolsindicatechangingenvironmentalconditions.
Figure2-13Generalmodelofhierarchicalcontrolstructure
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
45
2.5 ProcessModelforeachSystemComponent
Thepotentialforinadequatecontrolforeachsystemcomponent–whichcouldultimatelyleadtothe
hazardsdefinedinChapter2.3–wasanalysedbytheauthor.Forasummarizeddescriptionforeach
systemcomponent,refertoKAppendix.
According toSTAMP (Leveson,2011), accidentsaredescribed in suchaway thateachhigher level
controlstheactivityatthe levelbelowbymeansofcontrolhierarchiesandadaptationoffeedback
mechanisms.Thisadaptationisespeciallyimportanttoavoidfutureaccidents.Theunderstandingof
theprocessandhowhigherlevelsinthecontrolstructurecontributedtounsafecontrolactionswas
emphasized.Therefore,thesafetycontrolstructureofindividualsystemcomponents(Figure2-14to
Figure2-22)wassimplifiedtotherelevantinteractionsandthefollowingsafety-relevantfactswere
modeled.Finally,theresultswerecategorizedaccordingly:
• Unsafecontrolactions(UCA)
• DysfunctionalInteractions
• Contextualfactors
• Identified Safety requirements and constraints (SC)with the link to associated hazards, as
definedinChapter2.3
• Questionsraised(QR)
TUGrazIMasterthesis
STAMPAnalysisoftheN4252GAccident
46
2.5.1 HigherControlLevel(HCL)-ControlStructure
TheauthorhasdefinedtheHCLasasummarizedtermforthehighestleveloftheHCS.Itdescribesall
higher-level control structures (such components as legislature, government regulatory agencies,
aviationauthorities,pilot’sassociationsandunions).
Figure2-14HCL-simplifiedcontrolstructure
HCL-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
Thelegislaturehasthepowertoenforcenewstandards/regulations.Accidentinvestigationprocessesarehardlyinvestigatedconsideringsystem-theoreticprinciples.Aviationauthorities,pilot’sassociationsandunionsmaydisseminatelessonslearnedandprovideexperience/knowledgeinrespectofflightsafety.
[SC-1_HCL]ThecompetentcomponentsoftheHCLshallemphasizetodisseminatelessonslearnedandenforceflightsafetyrecommendations(consideringsystem-theoreticprinciples)intostandards/legallaw[H-1,H-2,H-3,H-4,H-5].
TUGrazIMasterthesis
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HCL-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
USflighttrainingregulationsforprivatepilotsarerathermaneuver-basedthancoveringreal-worldchallenges,whereasindustrystandardslikeFITSprovidescenariobasedtraining(includingSRM,decisionmaking,riskmanagement,etc.).
[SC-2_HCL]Considerationofindustrystandardsandtechnologicalpossibilitiesshallbepartofthelegalenforcementbasisforgeneralaviationpilots’training[H-1,H-2,H-3,H-4,H-5].
Theinvestigationreportincorporatesnodetailsofknownincidentsofthepilottotheauthority.
[QR-1]Arethereanyincidentsknowntotheauthorityinrespectoftheaccidentpilot?
SRMcoursesarenotobligatory,whichmayresultinalackofSRMknowledge.
[SC-3_HCL]SRMCoursesshallberequiredforsinglepilotsonaregularbase[H-1,H-4].
Pilot’slicenceendorsementshavenoexpirydates,whichmayresultinpilotsexercisingtheirprivilegeswithoutfulfillingtheproficiencyrequirements.
[SC-4_HCL]Expirydatesofpilot’slicenseendorsementsshallbeimplemented[H-1,H-4,H-6].
HCLarenotreceivinginformation/feedbackofUSpilotsexceedingbiennialflightreviews.
[SC-5_HCL]Flightreviewdatashallbetrackedbythecompetentauthority[H-6].
RegularcheckridesforVFRsingle-enginepistonpilotsarenotrequiredbyregulation.
[SC-6_HCL]HCLshallemphasizetoenforceregularcheckridesforVFRsingle-enginepistonpilots[H-1,H-4].
Loss-of-controltrainingisnotobligatoryforsingle-enginepilots.
[SC-7_HCL]Loss-of-controltrainingforsingle-enginepilotsshallberequired[H-3,H-4].
Aircraftparachutesystemtrainingisnotobligatoryforflightcrews,asactualtrainingrequirementsarenotcoveringallmodernsystemstandards.
[SC-8_JCL]HCLshallemphasizetoenforcetrainingrequirementsbasedonmodernindustrystandards(e.g.APStraining)[H-5].
Stressmanagementeducation,especiallyforprivatepilots,isnotenforcedbytheHCL.
[SC-9_HCL]Stressmanagementeducationforpilotsingeneralshallberequiredonaregularbase[H-7].
ATSAPisareportingprogram,butonavoluntarybaseonly.Knownsafetyissuesmightnotberesolved,ifnotreported.
[SC-10_HCL]ReportingprogramsshallbeobligatoryforATCcenters[H-7,H-8].
Auditproceduresraisingnon-compliances(findings)inrespectofcommunicationdeficienciesamongATCCenters(requiringinstantaneouslycorrectiveactions)arenotexistent.
[SC-11_HCL]RegularauditsatATCcentersshallbeaccomplishedaspartoftheoversightthroughHCL.Non-compliancesshallbeanalysedforitsrootcausesandrespectivecorrectiveactionsapplied[H-8].
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HCL-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
HCLprovidenopro-activeoversightmeasurestoprohibitflightcrewsperformingtheirdutyundertheinfluenceofmedicationswithoutAMEapproval.
[SC-12_HCL]MeasuresmustbeenforcedtoprohibitpilotsperformingtheirdutiesundertheinfluenceofprescriptionmedicationswithoutAMEapproval[H-1,H-7].
PrimaryaccidentcausalfactorsthatcontinuetoplaguethegeneralaviationcommunityhadnotbeenexplicitlydisseminatedbyHCLaslessonslearned.
[SC-13_HCL]Primaryaccidentcausalfactorsthatcontinuetoplaguethegeneralaviationcommunityshallbeexplicitlydisseminatedtothepilots[H-1,H-3,H-4].
Table2-2HCL-CASTanalysis
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2.5.2 TrainingOrganisation15-ControlStructure
Figure2-15Trainingorganisation-simplifiedcontrolstructure
TrainingOrganisation-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
Theprevailingdocumentsprovidednoinformationabouttheinitialtrainingoftheaccidentpilotandherprogress.
USpilottrainingisprovidedeitherthroughFAA-certificatedpilotschools(rf.Title14CFRpart141)orthroughothertrainingproviders(rf.Title14CFRpart61).Sometrainingorganisationsprovidescenariobasedtrainingaccordingindustrystandards(e.g.FITS).
[QR-2]Statedetailsabouttheinitialtrainingoftheaccidentpilotandherprogress(type/duration,typesofaircraft,detailsaboutdescentplanning,energymanagement,busyairportoperations,stabilizedapproachcriteria,stall/spinavoidance,CAPS)?
TheCFI-1statedthatduringthefirstflightsoftheaccidentpilot’sinstrumenttrainingeverysituationwashandledcomparabletoanystudenttheCFI-1hadworkedwith.TheCFI-1flewthreeflightswiththeaccidentpilot(September,2015).
[QR-3]Whatwasthestatus/progressoftheaccidentpilot’sinstrumenttraining?
15Author’s note: Given that the accident report does not describe any details, “training organisation” wasdefined as generic term substituting all organisations and flight instructors where the accident pilot hadreceivedflighttraining.
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TheCFI-2flewwiththeaccidentpilottwice.Bothflightswererecurrenttrainingflights.Hestatedthatthepilothandleditwithinacceptablelevelsandretainedcomposureandtheabilitytoflytheairplane.
[QR-4]WhathadbeentheweaknessesoftheaccidentpilotintheopinionoftheCFIs?
“Spinentrycanbeavoidedbyusinggoodairmanship:coordinateduseofcontrolsinturns,properairspeedcontrol,noacceleratedflightcontrolinputswhenclosetothestall”(POH-SR20,2015,p.3-28).
[QR-5]Wasgoodairmanshipinrespectofspinavoidance(asmentionedinthePOH)trained?
Theweatherconditionsatdestinationwereconsideredassuitableforlandingbythepilot.Itisnotassuredifthepilothadadequateknowledge,thatthewindlimitwasexceedingthepersonallimitsaccordingtotheCirrusFOM(EnvelopeofSafety).
[SC-14_TrgOrg]Trainingorganisationsmustassurethatpilotsareproficientinallrelevantaircraftmanualcontents(POH,FOM)oftheaircraftoperated[H-7].
[QR-6]WastheFOMwiththe“EnvelopeofSafety”taughtaspartoftheinitialtrainingfortheCirrusaircraft?
Riskawarenesswasacausalfactoroftheaccident.
[SC-15_TrgOrg]Riskawarenesstoolsshallbetrainedtopilotsconsideringactualinfluencingfactorsforinstructionflights.
Lackofpilot’sstress-andworkload-managementinfluencedtheoutcomeoftheaccident.
[QR-7]DidthepilotattendanycoursesinSRMorrelatedtopicsandwhathadbeenthecontent?
Lackofpilot’spro-activesafetycultureinfluencedthesafetyofflight.
[SC-16_TrgOrg]Procedurestokeeppro-active,personalSafetyCulturesineverypilot’smindshallbeenforced[H-6].
[QR-8]Howwasthepilot’sattitudeinrespectofherownsafetyculture?
TheCAPSwasnotactivatedwhentheaircraftenteredaspin.Itisnotassuredifthepilothadadequateknowledgeforproceduralbehaviourincaseofaircraftupsetand/orspin.
[SC-17_TrgOrg]Practicaltraininginacrobaticaircraft/simulatorstomaintainproficiencyinspinrecoveryproceduresshallbeenforced[H-5].
[QR-9]Wastheaccidentpilottrainedtorecognizelossofcontrolsituationsandhowtoescape?
Table2-3Trainingorganisation-CASTanalysis
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2.5.3 ATC-ControlStructure
Figure2-16ATC-simplifiedcontrolstructure
ATC-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
TheFLMstatedthatcommunicationthroughoutthefacilityinHOUhadrequiredimprovement.
[QR-10]WhichcommunicationprocessesattheHOUATCFacilityrequireimprovements?
Reducednumberofcontrollers,asoneofthecontrollersassignedtotheshifthadbeenmedicallydisqualifiedandanothercontrollerhadalreadybeenapprovedforhisannualleave.TheactivitylevelplacedthefacilityrightinthemiddleoftheATC8levels.
[SC-18_ATC]ItmustbeassuredthataminimumnumberofATCcontrollersisavailabletoavoidanydegradationinaviationsafety[H-7,H-8].
TheLCTwasnotsurewhytheOJTIhadtakenoverthefrequencyinsteadofjusthavinghimissuetheclearance.
ThefrequencywashandedoverafewtimesbetweentheLCTandtheOJTI(LCI).
[SC-19_ATC]OperationswithATCtraineesbeingsupervisedbyATCinstructorsmustfollowclearandconsistentprocedures[H-7,H-8].
[QR-11]WaspeerpressureinfluencingthecommunicationbetweentheATCtraineeandhisinstructor?
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ATCSimulatortrainingwasnotprovidedfortheLCposition,radartrainingwasprovidedviaonlinelearningtools.
[SC-20_ATC]ATCtrainingshallincludeactiveATCsimulatorsessionsratherthanonlinelearningtools[H-7,H-8].
[UCA-1]ATCrevisedtherunwayassignmentsforlandingafewtimeswithinashorttimeinterval,whichresultedinanincreasedpilot’sworkload.
[SC-21_ATC]ATCshallnotchangerunwayassignmentsforlandingwithinashorttimeintervaltoavoidunnecessarilyincreasingtheworkloadforthepilot.[H-7,H-8].
[UCA-2]ATChadnoreportsofwindshearorotherwindissuesuntiltheafternoon,whichresultedinassignmentofrunway4/35insteadofrunway12forarrivals(whichwasmoreconvenientduetothewindconditions).[UCA-3]ATCdidnotadapttherunwayassignmentsforthelowestachievablerisks,whichresultedinanavoidablecrosswindcomponentfortheactiverunway35.
“Thetowerwasnotprimarilyusingrunway12forarrivalsbecausethewindhadn’tpickedupuntiltheafternoonarrivalpushwasinprogress,andthatwasnotagoodtimetochangerunways”(rf.(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.25)).
[SC-22_ATC]Runwayassignmentsshallbeadaptedforthelowestachievableriskinchangingwindconditions[H-7].
Theaircraftwasseparatedveryclosetootherapproachingaircraft.
[QR-12]Whichalternativeprocedures(exceptvisualseparation)forre-aligningaircraftinthetrafficpatternwerecommon?
[UCA-4]TheCirruswasvectoredtorunway35withtheexistingcrosswind(gustsupto20kts),althoughdifficultiesforthepilotinhandlingtheaircraftwereobvious.
TheFLMsaidthatthetowerhadbeenusingrunway35alldayforavarietyofaircraftwithnoissues.
[SC-23_ATC]RunwayassignmentproceduresforATCshallbeenforcedtoreducecrosswindcomponentsforaircraftapproachingwithobviousdifficultiesinaircrafthandling[H-7].
TheLCTstatedthattheaircraftappearedtobedefinitelytoohightolandafterbothapproachescarriedouttorunway35.
[SC-24_ATC]ATCtowercontrollersshallbetrainedtoprovideappropriateclearancesiftheaircraftisinaposition(“unstableapproach”)fromwhichasuccessfullandingcannotbeassured[H-9].
[UCA-5]Non-adherencetoICAOstandardphraseologycausedmisunderstandingsbetweenpilotandATC.
AnATCclearancetoturnrightwithoutaheadingassignmentisnotaccordingstandardICAOphraseology.
Applicationofnon-standardICAOphraseology(“keepittight”,“leftheading30degrees”)TheLCCwasaskedaboutthe“lowandtight”instruction,heansweredhehadgiveninstructionslikethattootherpilotsaswell.
[SC-25_ATC]AdherencetoICAOstandardphraseologyshallberegularlyevaluatedandexamined.Importanceofclearcommunicationshallbehighlighted[H-7,H-8].
[QR-13]AretheATCcontrollerstrainedtofollowICAOstandardphraseologyandtoavoidunnecessarilylongATCclearances,especiallyduringcriticalphasesofflight?
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ATCclearanceto1600ftMSLforkeepinganaircraftinthetrafficpatternrequiresclarificaton.
[QR-14]DotheLCcontrollershaveadequatetrainingforvectoringaircraftinthenearproximityoftheairportunderhigh-trafficconditions?
[UCA-6]KeepingtheaircraftinthetrafficpatterninsteadofhandingitovertotheApproachControllerincreasedthepilot’sworkload.
Non-adherencetotheletterofagreementwasaverystandardalternateplan.
FacilityBriefingandaletterofagreementstatedtotransfergo-aroundaircraftbacktotheapproachcontrolforresequencing.FortheLCIkeepingtheaircraftinthepatternwasthe“normal”response.TheLCCstatedthatifageneralaviationaircraftwentaroundhewouldprobablyhavekepttheaircraftratherthangivingitbacktoapproach.TheFLMstatedthatabout90%ofthetimeifasmallVFRaircrafthadtobere-sequencedoffrunway4,thetowerwouldhavekepttheaircraftandnothandeditofftoapproach.FortheI90controlleritwasusual,thatVFRtrafficwasworkedbackforlandingbyHOUtower.iftheyhadnotbeenabletodothat,thenI90wouldhavetakenthego-aroundaircraftbacktore-sequenceitforanotherapproach.
[SC-26_ATC]ClearATCProceduresshallbeenforcedandadheredtoassurethatsafetyhasfirstpriority.HandingoverofVFRaircrafttoapproachcontrolmustnotbecategorizedasabnormal[H-7,H-8].
Whenthepilotadvisedaboutheruncertaintyofbeingcorrectlylinedup,theATCjustcancelledthestraight-inapproachinsteadofsupportingtoregainthesituationalawareness.
[SC-27_ATC]ATCcontrollersshallbetrainedtorecognizeandsupportpilotsinregaininglostordegradedsituationalawareness[H-7].
[QR-15]WasLCcontroleverindoubt,thatN4252Gmightnotbeabletolandtheaircraftsuccessfully?
AccordingtheLCTController,thepilotneversoundedflusteredordisoriented.AccordingtotheI90Controller,thepilotofN4252Gsoundedconfident.
[QR-16]HowdoesanATCcontrollerevaluatetheconfidenceofpilots?
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Theapproachcontrollerwasrequiredtocontinuetomonitorthespacingonfinalevenafteraircraftwereswitchedtothetower.TheFLMcalledapproachandaskedthemtoslowtheirnextarrivaldownformorespacefortheCirrus.ThiswasnotcoordinatedwithLC.TheI90controllerdidn’tthinkHOUtowercouldsequenceN4252Ginsideofthetraffic.
Approachcontrol(I90)toldtheFLMthathewouldtakeN4252Gback,buttheFLMsawthatN4252Gwasalreadyturningbase,sohetoldapproachthatthetowerwouldjustworktheaircraft.ThiswasnotcoordinatedwithLC.TheFLMdidnotgiveanyinstructiontoLCastheyseemedtohavethesituationundercontrol.
[SC-28_ATC]TheinternalcommunicationprocessamongATCstationsshallnotbeimpaired[H-7,H-8].
[UCA-7]ATCtransmittedunnecessarilylongtothepilotgoing-around,whichresultedindistractionduringacriticalphaseofflight.
[SC-29_ATC]ATCtransmissionstoanaircraftinacriticalphaseofflightshallbekepttoaminimum[H-7,H-8].
[QR-17]DidtheLCCanticipatethehighworkloadandstressthatthepilotofN4252Gwasunderatthethirdgo-around?
[UCA-8]TheLCIwasrelievedbytheLCCinabusyandcriticalmoment(thirdgo-aroundofN4252G)afteronly2-minutesofoverlap(whichistheminimumrequiredperiod).Itcausedinsufficientsituationalawarenessforthecontrollertakingover.
LCIsshiftwasending.TheFLMhadarrangedtorelievetheLCI.TheLCCmovedtothemonitorpositionfortherequired2-minutepositionoverlapperiod.
[SC-30_ATC]OverlapperiodsofATCcontrollersshallbeadaptedtotheactualscenarioandnotbebasedsolelyonoverlap-time[H-7,H-8].
[QR-18]Howwasassured,thattheLCCtakingoverhadsufficientsituationalawarenessabouttheATCtrafficsituation?
TheFLMhadtriedtogetcrewbriefingstogethersincehegottoHOU,butstaffinghadbeenshortandbriefingshadbeenhardtoaccommodate.Somecontrollershadneverseencertainsituations.Valueoftheseexperienceswerenottaughtwellenough.
FortheLCI,havinganaircraftmisstherunwaytwicewasthefirsttimehehadseenthat.TheLCIhasnotparticipatedinanycrewbriefingsincehecametoHOU.Accordingtohim,therewasnopracticeofdiscussingincidentsandaccidentsaslearningexperiences.TheLCCstatedthathehadnotattendedmanycrewbriefingsinthepastfewyears,andthattheywerenotregularevents.
[SC-31_ATC]RegulartrainingeventstoshareeachATCcontroller’sexperiencesshallbeaccommodated[H-8,H-9].
[QR-19]HowisitassuredthatindividualproceduresandworkingpracticesaresharedamongeveryATCteammember?
TheFLMhadnotcompletedmanyPRCstodocumentcontrollerperformance(headmitteditasanerroronhispart).PoordocumentationofperformancemanagementbytheFLM.
[QR20]HowwastheperformanceofATCcontrollersassured?
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ATC-CASTanalysisUnsafecontrol
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ATSAPreportswerenotappliedinHOU.
[SC-32_ATC]Non-punitivereportingculturesforATCcontrollersshallbeobligatoryforeachATCcenterforahigherlevelofexperienceexchange[H-1,H-7,H-8,H-9].
Table2-4ATC-CASTanalysis
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2.5.4 AircraftManufacturer(Cirrus)-ControlStructure
Figure2-17Aircraftmanufacturer-simplifiedcontrolstructure
AircraftManufacturer-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
ThePOHinVersionA1hasbeenvalidandunrevisedsinceDecember29,2015.
[QR-21]WhatschedulestheissueofnewPOHrevisions?
[UCA-9]“TheonlyapprovedanddemonstratedmethodofspinrecoveryisactivationoftheCAPS”(POH-SR20,2015,p.3-28).Possiblealternativeproceduresforspinprevention/recoveryarenotprovidedinPOH,resultinginlimitedmentalprocessmodelsforthepilotincaseCAPSisnotactivated/available.
[QR-22]WhatisthealternativeprocedureforpilotsiftheCAPSsystemcannotbeactivatedincaseofanunintendedspin?
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AircraftManufacturer-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
ThePOH-SR20(2015)states,thattheSR20istrimmedbyadjustingtheneutralpositionofthecompressionspringcartridge(rf.(POH-SR20,2015,p.7-8,7-10)),whichprovidesanartificial“forceagainstaspringcartridge”onthecontrolyoke.Theassociatedrisksofspring-cartridgesarenotdescribedinthePOH.
[SC-33_Cirrus]UnusualartificialfeelingsonacontrolyokeanditsassociatedrisksshallbedescribedinthePOH[H-1,H-2].
[QR-23]Wasthepilotawareoftheassociatedrisksdueartificialaerodynamicforcesonthecontrolyoke?
TheflapswereextendedaboveVfe.
[SC-34_Cirrus]Improperpilot’sactionsexceedingaircraftlimitationsorendangeringthesafetyofflightshallbeavoided[H-1].
. LimitedAircraftFeedbackfornextflapsetting(speedscaleonairspeedindicator).
Theflapswereretractedbelowtherecommendedflapretractionspeedcausingtheaircrafttostall.
[SC-35_Cirrus]ThePOHshallclearlystateawarningthatretractingflapsbelowtherecommendedstallspeedsisofutmostdangeroflosingcontroloftheaircraft[H-1,H-4].
N4252Gwaslostduetotheinabilitytoregainaircraftcontrol.
“LossofControlisoneofthesixmostcriticalandcommoncausesofGA[generalaviation]accidents”(USDepartmentofTransportation,AC61-98D(supersedesAC61-98C),2018,p.2-1).
[QR-24]HowdoesthemanufacturerassurethatLOCisavoidedinCirrusaircraft?
Table2-5Aircraftmanufacturer-CASTanalysis
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2.5.5 COPA-ControlStructure
Figure2-18COPA-simplifiedcontrolstructure
COPA-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
“TheCPPPisdesignedtoexposeCirruspilotstosituationstheymayencounterwhileoperatingtheiraircraft”(FOM-SR20,2011,p.2-4).
[QR-25]DidtheaccidentpilotparticipateinanyCPPPtraining?
“TheCDMseminarisafacilitatedinteractivehangar-flyingsessionwherethegrouplooksatgeneralaviationandCirrusaccidentstatistics,reviewscasestudiesofCirrusaccidents,andparticipatesinthereenactmentofanactualaccident”(FOM-SR20,2011,p.2-4).
[QR-26]DidtheaccidentpilotparticipateinanyCDMseminar?
“ThePartnerinCommandseminarhasbeendesignedtogivefrequentCirruspassengersmoreknowledgeregardingsafetysystemoperations”(FOM-SR20,2011,p.2-4).
" [QR-27]DidanyofthepassengersparticipateinaPartnerinCommandseminar?
Table2-6COPA-CASTanalysis
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2.5.6 HOUAirport-ControlStructure
Figure2-19HOUairport-simplifiedcontrolstructure
HOUAirport-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
ThecontentsoftheactualNOTAMsandweatherforecastsonthedayofaccidentisnotmentionedintheaccidentinvestigationreport.
[QR-28]DidtheactualNOTAMsatthedayoftheaccidentstateanydeficienciesinfluencingthesafetyofflight(e.g.unserviceabilityofPAPI,displacedthresholds,etc.)?
TheATCcontrollerswerenotinformedoftheexactlocationofthewindsensor,thereforeanexactwindassignmentwasnotachievable.
TheFLMstatedthathewasnotsurewherethewindsensorwaslocatedontheairport,butnotedthattherewassoontobeachangeinthesystem.
[SC-36_HOU]ATCcontrollersshallbeinformedwherethewindsensorsarelocatedtoassigntheactualwindproperly.
Table2-7HOUairport-CASTanalysis
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2.5.7 Operator/AircraftOwner-ControlStructure
Figure2-20Operator/Aircraftowner-simplifiedcontrolstructure
Operator/AircraftOwner-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
NeithertheofficialaccidentreportnorrecherchesbytheauthorofthisthesisprovideddetailsaboutrequirementsoftheownertopermitapilottooperateN4252G.
[QR-29]Underwhichpre-requisitesdidtheoperator/aircraftownerpermitthepilottooperatetheaircraft?
[UCA-10]Theoperatorpermittedtooperatehisaircraftbyapilotwithoutavalidbiennialflightreview,whichcausedthepotential,thatthepilot’slackofproficiency,skillsandaeronauticalknowledgehadbeenundetected.
[QR-30]Whatwastheoperator’s/aircraftowner’ssafetypolicy(requirements,currency,training)forpilotsoperatingtheaircraft?
Table2-8Operator/Aircraftowner-CASTanalysis
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2.5.8 Pilot-ControlStructure
Figure2-21Pilot-simplifiedcontrolstructure
Pilot-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
Pilot’sgeneralexperienceonthetypeandothertypesofaircraft.Note:Theprevailingdocumentationdoesneitherstatedetailsreferringtopilot’sflighthours/landings(flighthourswithinthelast12months,pilot’slandingsintotal/within12months/within3months)nortoexperiencesonvarioustypes.
[QR-31]Whatarethedetailsconcerningtheaccidentpilot’stypesofaircraftflown,flighthoursandlandings.
Properflightpreparation.Note:Nodocumentationsabouttheflightplanningpackagewasfound.
[QR-32]DidthepilothaveaflightplanningpackageincludingweatherforecastandNOTAMs?
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Riskassessmentprocedure.Note:Nodocumentationsabouttheapplicationofriskassessmenttoolsthroughthepilotwasfound.
[QR-33]Didtheaccidentpilotapplyanyriskassessmenttools?
[UCA11]Thepilotperformedactivedutiesundertheinfluenceofaprescriptionmedication(“Zolpidem”)thatmayimpairmentaland/orphysicalabilityinconductingpotentiallyhazardoustaskssuchasflying(NTSB,AviationAccidentFinalReport,2017,p.8).
[SC-37_Pilot]Performingactiveflightdutiesundertheinfluenceofprescribedmedication,whichhasnotbeenaeromedicallyprescribed,shallbestrictlyprohibited[H-1,H-3,H-4,H-5,H-7,H-9].
[QR-34]Didthepilotwaitatleast24hoursaftertakingZolpidembeforeherflyingactivity(asrecommendedbytheFAA)?
ThepilothadnotflowntoHOUairportbefore.HOUisahigh-traffic,class-B(airspace)airport.
[SC-38_Pilot]Theimportanceofproperflightplanningandpreparationshallbeemphasized[H-7].
[QR-35]Howdidthepilotpreparefortheflightandwhathadbeenthecontentsoftheflightplanningpackage?
[UCA-12]Thepilotdidnotassesstherisksforthecrosswindcondition,whichresultedinanexceedanceoftherecommendedwindlimitaccordingtotheCirrusFOM(EnvelopeofSafety).
ThePOH-SR20(2015)statesthat,operationindirectcrosswindsof20ktshasbeendemonstrated(rf.(POH-SR20,2015,p.4-21)).
[SC-39_Pilot]Riskassessmentshallbeperformedbeforeandregularlyduringaflighttobepreparedforrapidlychangingconditionsinthedynamicaviationenvironment[H-7].
[QR-36]Whatwasthepilot’sattitudeinrespectofriskassessment?
[UCA-13]ThepilotdidnotprotestaboutthepermanentlychangingcoursesofactionbyATC,whichresultedinanincreasedworkload.
LackofAssertiveness. [SC-40_Pilot]PilotsshallbetrainednottoacceptATCclearancescausingworkload,whichisexceedingthepersonalcapabilities[H-1,H-8,H-9].
Noevidencewasfoundthatthepilothadaccomplishedasatisfactoryflightreviewwithinthepreceding24calendarmonths(rf.(Title14CFR61.56(c)).
Therelativelyhighexperience(>300hourswithin2yearsofflying)ontheSR20aircraftprovidedthepilotamisleadinglevelofconfidence.Skillsofperformingsafety-relevantmaneuvers(stabilizedapproaches,go-aroundmaneuvers,slowflight,stallrecognitionandrecovery,recoveryfromunusualattitudes,spinrecognitionandavoidance)hadlacked.
[SC-41_Pilot]Safety-relevantmaneuversshallbeperformedstrictlyaccordingtoprocedures[H-1,H-9].
[QR-37]Didthepilotperformanytrainingflightsoraflightreviewbeforetheaccident?
UncertaintyabouttheATCintentionsexistedThepilotgotdisorientedandlosttheclearpicturewheretherunwayshouldbelocated.
Lossofsituationalawarenessmaybeinfluencedbychannelizedattention(tunnelvision),distractionandtasksaturation.
[SC-42_Pilot]Theimportanceofsterilecabinproceduresshallbeemphasized[H-7].[SC-43_Pilot]Methodsandproceduresforrecognizingandregaininglostsituationalawarenessshallbetaught[H-3].
[QR-38]Wasthepilot’slevelofsituationalawarenessimpairedbyanyreasonandcouldthepilotingeneralbedistractedeasilywhenperformingtasks?
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[UCA-14]ThepilotdidnotprioritizetostabilizetheflightpathbeforecommunicatingwithATCduringcriticalphasesofflight,whichdistractedandincreasedtheworkload.
[SC-44_Pilot]Communicationannouncementsshallbeperformedaftertheflightpathissafelystabilized(“aviate-navigate-communicate”procedure)[H-1,H-7].
[UCA-15]Pilottaskswerenotprioritizedcorrectly,whichresultedinalossofsituationalawareness.[UCA-16]Thepilotaccepted,thatATCwaskeepingtheaircraftinthepatterninsteadofrequestingalternativemeasurestolowerherworkload.
Pilot’sworkloadwasnotreduced.
Thepilotwassubjecttohighworkload(“seeandavoid”separation,waketurbulencehazard,changingcomplexATCclearanceswithinshorttime,complexmaneuvers,passengers).Thepilotlackedassertiveness.Peerpressuretolandtheaircraftattheplanneddestinationwasexistent(“thirdtimewillbeacharm”).
[SC-45_Pilot]TheimportanceofSRMtrainingcoursesshallbeemphasizedtoprovideprocedurestocopewithhighworkloadsituations[H-7].
[QR-39]WasthepilottrainedinSRM?[QR-40]Hadthepilotbeensubjecttotimepressure(appointment)onthedayoftheaccident?
[UCA-17]Theflapswereextendedto50%ataspeed>10ktsaboveVfe,whichresultedinexceedingtheapprovedandsafeflightenvelope.
ATCadvisedthepilottokeepthespeedup.Thepilotdidnotannouncetheinabilitytocomply.
[SC-46_Pilot]IfATCrequestscannotbecompliedwith,proceduresforenergyandATCmanagementshallbeenforced[H-1,H-9].
[UCA-18]Safeairspeedcontrolwasnotachieved,whichresultedinexceedingtheapprovedandsafeflightenvelope.[UCA-19]Whentheapproachspeedwasdeceedingtherecommendedspeed,thepitchanglewasnotreducedandthespeeddecreasedfurtheruntilstall.
Thepilotmighthavemistakenprocedures/airspeedswithotheraircraftflowninthepast.
[SC-47_Pilot]Proceduresforcorrectairspeedcontrolandsubsequentaircrafttrimshallbeenforced[H-1,H-7,H-9].
[QR-41]Didthepilotactivelyoperateonothertypesofaircraftintherecentpast?[QR-42]Wasthepilotapplyingcorrecttrimprocedures?[QR-43]ArethereanyRDMdataavailableinregardsofaircrafttrim?
[UCA-20]Thepilotdidnotstartthefinaldescentappropriatelyinrespectoftheaimingpoint,whichresultedinendinguptoohighforthelanding.
Visualillusion(falseadoptionofhorizonafterlongcruiseflights)affectsstabilizedapproachcriteriaandcontrolofaircraft.
[SC-48_Pilot]Procedurestocopewiththeinfluenceofvisualillusionsshallbeenforced[H-1,H-9].[SC-49_Pilot]Proceduresfortheconsiderationofvisualglideslopeindications(PAPI)shallbeenforced[H-1,H-9].
[QR-44]Wasthepilotawareofpossiblevisualillusions?
[UCA-21]Stabilizedapproachcriteriawerenotfulfilled,whichresultedinendinguptoohighforthelanding.[UCA-22]Thepilotdidnotmanagetheglideanglewithflapsand/orside-slipasnecessary(rf.(FOM-SR20,2011,p.4-11)).
Theaircraftwasnotslowedtoaspeedthatallowedthepilottoperformastabilizedapproachinatimelymanner(rf.(FOM-SR20,2011,p.3-58)).
Modern,efficientwingdesignsproducelowdragandspeeddeductionmightsuffer.Side-slipmaneuversmaybeusedtoincreaserateofdescentwithoutspeedincrease.
[SC-50_Pilot]Procedurestoperformproperenergymanagement(powercontrol,side-slipmaneuvers)tocomplywithstabilizedapproachcriteriashallbeemphasized[H-9].
[QR-45]Hadtherebeenanyincidentsbythepilotinrespectofunstabilizedapproachesatotherairports?[QR-46]Wasthepilottrained/assessedforside-slipmaneuvers?
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actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
[UCA-23]Thepilotoverbankedtheaircraft,whichresultedinexceedingmaximumbankanglesduringvisualmaneuvering.[UCA-24]Thepilotencountereduncertaintyabouttheactualaircraftposition(tocomplywiththeassignedATCclearances),whichresultedinuncoordinatedandunusualaircraftattitudesinlowaltitude.
Navigatingcomplexmaneuversdistractspilotsfrombasicaviating.
High-trafficsituationinclass-Bairspaceinthecloseproximityofanairportwithcrossingrunwaysrequireshighnavigationalcapabilitiestoavoiderrors.Unusualattitudesinlowaltitudesmaybeasignofuncertainnavigationcapabilities.Deficienciesinvisionmaydistractthepilotfromreadingthenavigationchartsproperly.Electronicchartsmayfail.
[SC-51_Pilot]Pilotsshallknowtoavoidhighbankanglesinlowlevelflying[H-1,H-9].[SC-52_Pilot]Navigationalchartsmustbeeasytoreadandhaveabackup[H-7].
[QR-47]Whichchartshadbeenusedasreferencefornavigation?[QR-48]Wasthepilotabletoreadthechartsproperly?
[UCA-25]ThepilotdidnotrecognizetheinabilitytolandfromtheactualpositionuntilconcernswereraisedbyATC(“ifthat’stoohighwecanputyouback[…],don’tforceitifyoucan’t”,“youmightbetoohigh”),whichresultedinago-aroundatalatestage.
Thelateandincorrectinitiationofthego-aroundmightbeasignforuncertaintyofago-aroundprocedure.
[SC-53_Pilot]Proceduresmustbeenforcedthatpilotsoncontrolarealwaysawarewhenandhowtoinitiateago-aroundtomaintainthehighestachievablelevelofsafetymargin[H-9].
[UCA-26]Theprocedureforbalkedlandings(go-arounds)wasnotfollowedcorrectly(fullpowernotapplied,incorrectspeeds,inadequatecoordination),whichresultedinexceedingtheapprovedflightenvelope.
Thego-aroundisacomplexanddemandingprocedure,asmanyactionsneedtobeperformedinashorttimeclosetotheground.Reducedpowersettingswerecontributing.
[SC-54_Pilot]Apilotmustbeabletoperformacorrectgo-aroundprocedureinanysituation,irrespectiveofexternalinfluences[H-9].
[QR-49]Whatwasthereasonforapplyingreducedpowersettingsforthego-around?
[UCA-27]Theincreasingtailwindcomponentloweringtheenergystateoftheaircraftwasneglected.
[SC-55_Pilot]Theinfluenceofwindcomponentsinperformanceshallneverbeunderestimated[H-1].
[UCA-28]StallWarningswereneglectedbythepilot,whichresultedinfurtherspeeddecrease.[UCA-29]Theaircraftwasstalleddueuncoordinatedpitchcontrolandretractionoftheflaps.
Lostsituationalawarenesscausesevenobviouswarningsignals(stallwarning)tobeignored.
[SC-56_Pilot]Measuresshallbeenforcedtomaintainthehighestlevelofsituationalawareness[H-7].
[QR-50]Wasthepre-flightcheckincl.stallwarningsystemcheckperformedproperly?[QR-51]DidATCrecordanystallwarningsignalsonthetransmissiontapes?[QR-52]DoestheRDMstoreanactivestallwarningtrigger?
[UCA-30]Controlovertheaircraftwaslostandnotrecovereduntilthefatalgroundimpact.
Thepilot“maybedisorientedbeyondthepointwheretraditional,handflownrecoverytechniquesareeffective”(FOM-SR20,2011,p.4-40).
[SC-57_Pilot]Procedurestoavoidandescapelossofaircraftcontrolshallalwaysbethefirstpriorityofanypilot[H-3,H-4,H-5].
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Pilot-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
[UCA-31]CAPShadnotbeendeployedbythepilotwhenrequired,whichresultedinanon-deceleratedaircraftimpactonground.
StartleEffectmayhaveaffectedthepilot’sabilitytocopewiththesituationontime.
referto[SC-61_Paxe] [QR-53]DidthepilotperformanyCAPStraining?
Table2-9Pilot-CASTanalysis
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2.5.9 Passengers-ControlStructure
Figure2-22Passengers-simplifiedcontrolstructure
Passengers-CASTanalysisUnsafecontrol
actionsDysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
Timepressureinfluencesdecision-making.
[QR-54]Wereanyofthepassengersontheflightundertimepressure?
Convectiveweathercausesturbulences.Medicalimpairmentorairsicknessofpassengersmightcausethepilottobedistracted.
[QR-55]Wereanyofthepassengersknownforairsicknessorotherphysiologicaldeficiencies?
Thepilotmaybedistractedbythepassengers(e.g.dueconversations,airsickness,fearofflying,etc.).
[SC-58_Paxe]Passengersshallbeawareofsterilecabinproceduresandavoiddistractingthepilot[H-7].
[QR-56]Hadpassengersbeenbriefedonsterilecabinprocedures?
Passengersmaysupportthepilotinhighworkloadenvironment(airspacescan,awarenessofstabilizedapproachcriteria,etc.).
[SC-59_Paxe]PassengersshallbeconsideredasaresourceinSRM[H-7].
[QR-57]Didthepassengersfrequentlyflywithsingle-enginepistonaircraftand/orhaveextensiveaviationknowledge?
Multiplego-arounds,highdescentrates,unusualattitudes,gustycrosswindconditionsandtherecognitionofhighworkloadforthepilotmayscarepassengersandcausedistractionsforthepilot.
[SC-60_Paxe]Pilotsshallbetrainedinprocedurestoprovideasafeandcomfortableatmosphereforpassengers[H-7].
[UCA-32]NoneofthepassengershadconsideredtoactivateCAPSwhenrequired,whichresultedinannon-decleratedaircraftimpactonground.
RegardingCAPSactivation“nominimumaltitudefordeploymenthasbeenset”(POH-SR20,2015,p.10-6).
[SC-61_Paxe]AnybodyonboardshallknowaboutactivatingCAPS,iflife-threateningsituationspersist(whichrequiresdetailedpreflghtbriefingforpassengers)[H-5].
[QR-58]Hadthepassengersbeenbriefedaboutlife-threateningsituationsrequiringtheactivationofCAPS?
Table2-10Passengers-CASTanalysis
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2.5.10 Aircraft-ControlStructure
Figure2-23Aircraft-simplifiedcontrolstructure
Aircraft-CASTanalysis
Unsafecontrol Dysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
[UCA-33]Thestallwarningsystemwasneglectedbythepilot,whichresultedinfurtherdecelerationandactualstalloftheaircraft.
[QR-59]Wasthestallwarningsystemfunctionableontheaccidentflight?[QR-60]Wasthepilotawareofaerodynamicaircraftreactionswhenapproachingstallconditions?
Safeairspeedcontrolwasnotachieved.
Theinabilitytoreadtheprimaryflightinformationdatafromthecockpitannunciationsmayleadtoexceedancesoftheapprovedflightenvelope.
[QR-61]WasthereanyfailureoftheprimaryflightdisplaysloggedbytheRDM?[QR-62]Didtheprimaryflightdisplayfailorgetinanunreadablecondition?[QR-63]Didtheaccidentaircrafthavealternateindicationsoftheprimaryflightinformation(speed,altitude,attitude)?
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Aircraft-CASTanalysis
Unsafecontrol Dysfunctionalinteractions Contextualfactors Safetyconstraints Questionsraised
Thetrimsettingoftheaircraftonimpactwasnotdocumentedintheinvestigationreport,whichwouldprovideaninformationaboutforcesonthepilot’syoke.
[QR-64]Forwhichspeedwastheaircrafttrimmedbeforethefinalimpact?
Dataoverloadthroughtheon-boardavionicsmayimpairtheabilityofpilotstoeffectivelyoperatetheaircraft.
[SC-62_Aircraft]Aircraftsystemindicationsshallbesimpletounderstandandread[H-7].
[UCA-34]Theaircraftincorporatesnoactiveattention-getterremindingofactivatingCAPSinlife-threateningsituations(spininlowaltitude),whichresultedinanon-deceleratedaircraftimpactwithoutactivatedCAPS.
Startleeffectimpairstheabilitytotakeappropriateaction.
[SC-63_Aircraft]ProceduresofactivatingCAPSinlife-threateningsituationsshallbebroughttonoticeableattentioninthecabin[H-5].
Table2-11Aircraft-CASTanalysis
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3 RESULTS
AsLevesonnoted“oneconsequenceofthecompletenessofaSTAMPanalysisisthatmanypossible
recommendationsmayresult-insomecases,toomanytobepracticaltoincludeinthefinalaccident
report. A determination of the relative importance of the potential recommendations may be
requiredintermsofhavingthegreatestimpactonthelargestnumberofpotentialfutureaccidents.
There is no algorithm for identifying these recommendations, nor can there be. Political and
situational factors will always be involved in such decisions. Understanding the entire accident
process and the overall safety control structure should help with this identification, however“
(Leveson,EngineeringaSaferWorld,2011,p.384).
The prevailing CAST modeling of the N4252G accident was based on available information and
detailedrecherchesbytheauthor.Emphasiswasplacedonunderstandinghowhigher levels inthe
hierarchical control structure influenced/ allowed unsafe control actions. The following safety
recommendationsaspartoftheresultsoftheSTAMP-basedanalysiswerecreatedbytheauthorin
relationtothedevelopedsafetyconstraints,consideringmeasurestoprotectthemfromerosionof
safetyovertime.FordetailsrefertothefollowingTable3-1Safetyrecommendations.
Safetyconstraints Safetyrecommendations
[SC-1_HCL] ThecompetentcomponentsoftheHCLshallemphasizetodisseminatelessonslearnedandenforceflightsafetyrecommendations(consideringsystem-theoreticprinciples)intostandards/legallaw.
[REC-1] Legallawshallbeadaptedinaway,thataccidentinvestigationprocessesareinvestigatedconsideringsystem-theoreticprinciplesandprovidesafetyrecommendations,whichareimplementedinthestandards/legislation.
[SC-2_HCL] Considerationofindustrystandardsandtechnologicalpossibilitiesshallbepartofthelegalenforcementbasisforgeneralaviationpilots’training.
[REC-2] Pilottrainingshallbebasedonmodernequipmentusedandonreal-lifescenarios(includingSRM,decisionmakingandriskassessment),ratherthansolelyonmaneuvers.Trainingstandardsyllabishallberevisedonaregularbase,consideringindustrytechnicalstandardsandlessonslearnedfromrecentaccidents/incidents.
[SC-3_HCL] SRMCoursesshallberequiredforsinglepilotsonaregularbase.
[REC-3] Regulartraininginsingle-pilotresourcemanagementshallbearequirementforpilotsexercisingtheirlicenses.
[SC-4_HCL] Expirydatesofpilot’slicenseendorsementsshallbeimplemented.
[REC-4] Pilot’slicenseendorsementsshallberestrictedbyexpirydates,whichrequirepre-requisiteswhichcanbeadaptedaccordinglybythelegislation.
[SC-5_HCL] Flightreviewdatashallbetrackedbythecompetentauthority.
[REC-5] Checkairmen(examiner)shallbeprovidedwithatooltoforwardproficiencyassessmentsofperformedflightreviewstothecompetentauthority,whichenablestotracktheflightcrews’proficiencystatus.
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Safetyconstraints Safetyrecommendations[SC-6_HCL] HCLshallemphasizetoenforceregularcheck
ridesforVFRsingle-enginepistonpilots.[REC-6] Checkridesshallberequiredtorevalidate
VFRsingle-enginepilot’slicenseendorsementsconsideringtheproficiencyofthepilot.Formoreexperiencedpilotstheintervalrequiredtorevalidatethelicensemaybeextendedondiscretionofthecheckairman(examiner).
[SC-7_HCL] Loss-of-controltrainingforsingle-enginepilotsshallberequired.
[REC-7] Loss-of-controltrainingforpilotsshallberequiredonaregularbaseandtrackedbytheauthority.
[SC-8_HCL] HCLshallemphasizetoenforcetrainingrequirementsbasedonmodernindustrystandards(e.g.APStraining).
[REC-8] Pilotsshallbetrainedinaircraftparachutesystemsonaregularbaseandtrackedbytheauthority.
[SC-9_HCL] Stressmanagementeducationforpilotsingeneralshallberequiredonaregularbase.
[REC-9] Stressmanagementeducationforpilotsincludingcoachingshallberequiredonaregularbase.
[SC-10_HCL] ReportingprogramsshallbeobligatoryforATCcenters.
[REC-10] ATCcentersshallapplyaformalsafetyreportingsystemaswellasanindependentfeedbackchannelaboutprocesssafetyconcernsbyemployees.
[SC-11_HCL] RegularauditsatATCcentersshallbeaccomplishedaspartoftheoversightthroughHCL.Non-compliancesshallbeanalysedforitsrootcausesandrespectivecorrectiveactionsapplied.
[REC-11] CompetentauthoritiesshallaccomplishregularauditsatATCcentersandraiseappropriatefindingsrequiringappropriaterootcauseanalysesandcorrectiveactionplans(aspartofthesafety-management-system).
[SC-12_HCL] MeasuresmustbeenforcedtoprohibitpilotsperformingtheirdutiesundertheinfluenceofprescriptionmedicationswithoutAMEapproval.
[REC-12] Unannounceddrugandalcoholtestprogramsofpilotsshallbeestablishedbythecompetentauthority.
[SC-13_HCL] Primaryaccidentcausalfactorsthatcontinuetoplaguethegeneralaviationcommunityshallbeexplicitlydisseminatedtothepilots.
[REC-13] Pilotsshallbepromotedtoengageinincentiveproficiencyplatforms(e.g.WINGS)toenhancetheirknowledgeofprimarycausalaccidentfactors.
[SC-14_TrOrg] Trainingorganisationsmustassurethatpilotsareproficientinallrelevantaircraftmanualcontents(POH,FOM)oftheaircraftoperated.
[REC-14] Measuresshallbeenforcedthatrelevantaircraftmanualcontentsarerefreshed/reviewedregularlybythepilots.
[SC-15_TrOrg] Riskawarenesstoolsshallbetrainedtopilotsconsideringactualinfluencingfactorsforinstructionflights.
[REC-15] Establishpromotionsabouttheimportanceofriskassessmentsatplacesfrequentlyattendedbypilots.
[SC-16_TrOrg] Procedurestokeeppro-active,personalSafetyCulturesineverypilot’smindshallbeenforced
[REC-16] Ensurethateverypilotunderstandsthatapro-active,personalSafetyCultureisofutmostimportance.
[SC-17_TrOrg] Practicaltraininginacrobaticaircraft/simulatorstomaintainproficiencyinspinrecoveryproceduresshallbeenforced.
[REC-17] Practicaltraininginacrobaticaircraft/simulatorstomaintainproficiencyinspinrecoveryproceduresshallberequiredbyregulation.
[SC-18_ATC] ItmustbeassuredthataminimumnumberofATCcontrollersisavailabletoavoidanydegradationinaviationsafety.
[REC-18] EnsurethatasufficientnumberofATCcontrollersisavailableandhavealternativemeasuresforunexpecteddeficiencies.
[SC-19_ATC] OperationswithATCtraineesbeingsupervisedbyATCinstructorsmustfollowclearandconsistentprocedures.
[REC-19] Supervisiontasksrequireclear,establishedprocedures,whichshallbebriefedtoeachotherbeforethefirstdutyoftheday.
[SC-20_ATC] ATCtrainingshallincludeactiveATCsimulatorsessionsratherthanonlinelearningtools.
[REC-20] ATCtrainingshallberegularlyperformedinATCsimulatorsformaximumbenefitofsafety.
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Safetyconstraints Safetyrecommendations[SC-21_ATC] ATCshallnotchangerunwayassignmentsfor
landingwithinashorttimeintervaltoavoidunnecessarilyincreasingtheworkloadforthepilot.
[REC-21] ATCre-clearancesrequiringashort-timedecision-makingprocessofthepilotoveranextendedperiodoftimeshallbeavoided.
[SC-22_ATC] Runwayassignmentsshallbeadaptedforthelowestachievableriskinchangingwindconditions.
[REC-22] Runwayassignmentsshallbeadaptedforcontinuouslyachievingthehighestlevelofpossiblesafety.
[SC-23_ATC] RunwayassignmentproceduresforATCshallbeenforcedtoreducecrosswindcomponentsforaircraftapproachingwithobviousdifficultiesinaircrafthandling.
referto[REC-22]
[SC-24_ATC] ATCtowercontrollersshallbetrainedtoprovideappropriateclearancesiftheaircraftisinaposition(“unstableapproach”)fromwhichasuccessfullandingcannotbeassured.
[REC-23] ATCcontrollersshallbetrainedtorecognizeunstableapproachconditionsandprovideappropriateclearancestoregainamaximumlevelofsafety.
[SC-25_ATC] AdherencetoICAOstandardphraseologyshallberegularlyevaluatedandexamined.Importanceofclearcommunicationshallbehighlighted.
[REC-24] AdherenceofATCcontrollerstoICAOstandardphraseologyshallbemonitored(regularstandardphraseologyexams)andappropriatetrainingmeasurestakenifneeded.
[SC-26_ATC] ClearATCProceduresshallbeenforcedandadheredtoassurethatsafetyhasfirstpriority.HandingoverofVFRaircrafttoapproachcontrolmustnotbecategorizedasabnormal.
[REC-25] ATChabitsshallbemonitoredforcompliancetoapplicableprocedures.Incaseofdeviationsre-evaluationstoregainthehighestlevelofsafetyshallbeapplied.
[SC-27_ATC] ATCcontrollersshallbetrainedtorecognizeandsupportpilotsinregaininglostordegradedsituationalawareness.
[REC-26] ATCcontrollersshallbetrainedtorecognizelostordegradedlevelsofsituationalawarenessofpilotsandhowtosupportthemtoregainamaximumlevelofsafety.
[SC-28_ATC] InternalcommunicationprocessesamongATCstationsshallnotbeimpaired.
[REC-27] ForinternalcommunicationamongATCstations,itshallbeassuredthatinformationconcerningtheactualtaskisforwardedtothecontrollersincharge.
[SC-29_ATC] ATCtransmissionstoanaircraftinacriticalphaseofflightshallbekepttoaminimum.
[REC-28] ATCcontrollersshallbetrainednottodistractpilotswithunnecessarilylongtransmissionsincriticalphasesofflight.
[SC-30_ATC] OverlapperiodsofATCcontrollersshallbeadaptedtotheactualscenarioandnotbebasedsolelyonoverlap-time.
[REC-29] ATCoverlapsshallnotbefinishedaslongasasufficientlevelofsituationalawarenessoftheATCcontrollertakingoverisnotachieved.
[SC-31_ATC] RegulartrainingeventstoshareeachATCcontroller’sexperiencesshallbeaccommodated.
[REC-30] ItshallbeassuredthatregulartrainingeventsofATCcontrollersareaccommodatedtoshareindividualexperiences.
[SC-32_ATC] Non-punitivereportingculturesforATCcontrollersshallbeobligatoryforeachATCcenterforahigherlevelofexperienceexchange.
referto[REC-10]
[SC-33_Cirrus] UnusualartificialfeelingsonacontrolyokeanditsassociatedrisksshallbedescribedinthePOH.
[REC-31] Itmustbeassuredthatapilotiswarnedofaircraftsystemswithunusualcharacteristicsandassociatedrisksinapropermanner.
[SC-34_Cirrus] Improperpilot’sactionsexceedingaircraftlimitationsorendangeringthesafetyofflightshallbeavoided.
[REC-32] ReferringtoFOM-SR20(2011),pilotsshallbedisciplinedtofollowstandardproceduresduringflightoperations,astheywilldevelophabitpatternsthroughrepetitionthatallowstobemostefficientwhilecompletingtasksandconfiguringtheaircraftforvariousphasesofflight(rf.(FOM-SR20,2011,p.3-3)).
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Safetyconstraints Safetyrecommendations[SC-35_Cirrus] ThePOHshallclearlystateawarningthat
retractingflapsbelowtherecommendedstallspeedsisofutmostdangeroflosingcontroloftheaircraft.
[REC-33] Itmustbeassuredthatapilotiswarnedofactionsthatcouldleadtoanimmediatelossofcontrol.Alternativemeasuresshallbeenforcedtoavoidinitiatingunsafeactions.
[SC-36_HOU] ATCcontrollersshallbeinformedwherethewindsensorsarelocatedtoassigntheactualwindproperly.
[REC-34] ATCcontrollersshallbeinformedaboutthelocationofmeteorologicalsensorsandtheapplicabilityofitsdata.
[SC-37_Pilot] Performingactiveflightdutiesundertheinfluenceofprescribedmedication,whichhasnotbeenaeromedicallyprescribed,shallbestrictlyprohibited.
referto[REC-12].
[SC-38_Pilot] Theimportanceofproperflightplanningandpreparationshallbeemphasized.
[REC-35] Pilotsshallbedisciplinedthatthepreparationofaproperflightplanningincludingriskassessmentisofutmostimportanceforthesafetyofflight.
[SC-39_Pilot] Riskassessmentshallbeperformedbeforeandregularlyduringaflighttobepreparedforrapidlychangingconditionsinthedynamicaviationenvironment.
[REC-36] Pilotsdecision-makingpre-flightandin-flight(withemphasizetorapidlychangingconditionsinthedynamicaviationenvironment)shallberelatedtoariskassessmentprocess,whichistrainedregularly.
[SC-40_Pilot] PilotsshallbetrainednottoacceptATCclearancescausingworkload,whichisexceedingthepersonalcapabilities.
[REC-37] PilotsshallbedisciplinedthatthePIChasthefinalauthorityforthesafetyofflight.Therefore,clearancesshallalwaysbeverifiedinrespectofsafetydeficiencies.Regularscenario-basedtrainingeventsindecision-makingandassertivenessshallbearequirement.
[SC-41_Pilot] Safety-relevantmaneuversshallbeperformedstrictlyaccordingtoprocedures.
[REC-38] Pilotsshallbestrictlydisciplinedthatitiseachairman’spersonalresponsibilitytomaintainskillstobepreparedinperformingsafety-relevantmaneuversanytimetheyareneeded.
[SC-42_Pilot] Theimportanceofsterilecabinproceduresshallbeemphasized.
[REC-39] Pilotsshallbeawarethatdistractionsmayseverelyimpairthesituationalawareness.Passengersmustbebriefedaboutsterilecabinprocedures.Placardstoremindintheaircraftcabinshallbeconsidered.
[SC-43_Pilot] Methodsandproceduresforrecognizingandregaininglostsituationalawarenessshallbetaught.
[REC-40] Pilotsoperatinginsingle-pilotoperationshallbeawarethat“stayingaheadoftheaircraft”allthetimeisofutmostimportance.IfalackofsituationalawarenessisrecognizedprocedurestoregainSAshallbeknownandappliedaccordingly.
[SC-44_Pilot] Communicationannouncementsshallbeperformedaftertheflightpathissafelystabilized(“aviate-navigate-communicate”procedure).
[REC-41] Itmustbethegoldenruleforanypilot,thatfirststabilizingtheflightpathandsecondnavigation(adherencetoATCclearances)haspriorityovercommunication.
[SC-45_Pilot] TheimportanceofSRMtrainingcoursesshallbeemphasizedtoprovideprocedurestocopewithhighworkloadsituations.
[REC-42] Considerationofallavailableresourcesmustbeperformed.Regularscenario-basedtrainingtoenhancethehighestachievablelevelofcompetenceshallbeemphasized.Workloadshallalwaysbemanagedinawaysoastomaintainsufficientpersonalcapacitiesforsafecompletionsofprimaryflightduties.
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Safetyconstraints Safetyrecommendations[SC-46_Pilot] IfATCrequestscannotbecompliedwith,
proceduresforenergyandATCmanagementshallbeenforced.
[REC-43] Stabilizedapproachcriteriashallbemonitoredbythepilot.Appropriatewarnings(“attention-getters”)shallbetriggeredbytheon-boardavionicsequipmentincaseofparametersdeviating.
[SC-47_Pilot] Proceduresforcorrectairspeedcontrolandsubsequentaircrafttrimshallbeenforced.
[REC-44] Pilotsshallbeawarethatirrespectiveofthelevelofautomationofanaircraft,thedisciplinetostrictlyfollowapprovedproceduresandmaintainbasicskillsinflyingisrequiredforasafeoperation.
[SC-48_Pilot] Procedurestocopewiththeinfluenceofvisualillusionsshallbeenforced.
[REC-45] Pilotsshallbeawarethatvisualperceptioninfluencesthepilot’sbasicflyingcapability.Vigilanceandregulartrainingshallbeensured.
[SC-49_Pilot] Proceduresfortheconsiderationofvisualglideslopeindications(PAPI)shallbeenforced.
[REC-46] Effectsofvisualillusionsinrespectofstabilizedapproachcriteriashallnotbeunderestimatedandregularlytrained.
[SC-50_Pilot] Procedurestoperformproperenergymanagement(powercontrol,side-slipmaneuvers)tocomplywithstabilizedapproachcriteriashallbeemphasized.
referto[REC-44]
[SC-51_Pilot] Pilotsshallknowtoavoidhighbankanglesinlowlevelflying.
[REC-47] Highbankawarenesssystemsshallbeintegratedintheaircraft’savionicssystem,towarnpilotsexceedingdefinedbankangles.
[SC-52_Pilot] Navigationalchartsmustbeeasytoreadandhaveabackup.
[REC-48] Pilotsshallassurethatthenavigationalchartsusedcanbereadandunderstoodunderallexpectedconditions.
[SC-53_Pilot] Proceduresmustbeenforcedthatpilotsoncontrolarealwaysawarewhenandhowtoinitiateago-aroundtomaintainthehighestachievablelevelofsafetymargin.
referto[REC-38]
[SC-54_Pilot] Apilotmustbeabletoperformacorrectgo-aroundprocedureinanysituation,irrespectiveofexternalinfluences.
referto[REC-38]
[SC-55_Pilot] Theinfluenceofwindcomponentsinperformanceshallneverbeunderestimated.
[REC-49] Pilotsshallbetrainedhowtodealwithenvironmentalfactorsinstantaneouslyinfluencingtheenergystateoftheaircraft.
[SC-56_Pilot] Measuresshallbeenforcedtomaintainthehighestlevelofsituationalawareness.
referto[REC-26]
[SC-57_Pilot] Procedurestoavoidandescapelossofaircraftcontrolshallalwaysbethefirstpriorityofanypilot.
[REC-50] Pilotsshallalwayshavefullcontroloftheaircraft.Forthecaseofinadvertentlossofcontrol,thepilotshallbetrainedregularlytoapplythesafestcoursesofaction.
[SC-58_Paxe] Passengersshallbeawareofsterilecabinproceduresandavoiddistractingthepilot.
referto[REC-39]
[SC-59_Paxe] PassengersshallbeconsideredasaresourceinSRM.
[REC-51] Designatedpassengersshallbeconsideredtoassistthepilotinresourcemanagement(e.g.readingchecklists,announcingdeviationsofbasicflightparameters,etc.).
[SC-60_Paxe] Pilotsshallbetrainedinprocedurestoprovideasafeandcomfortableatmosphereforpassengers.
[REC-52] Passengersshallbebrieflykeptinformedabouttheprogressofflightwithavoidinganymeansofscare.
[SC-61_Paxe] AnybodyonboardshallknowaboutactivatingCAPS,iflife-threateningsituationspersist(whichrequiresdetailedpreflghtbriefingforpassengers).
[REC-53] Passengersshallbebriefedaboutlife-threateningsituationsrequiringCAPSactivationand/orregularlycompleteaCAPStraining.
[SC-62_Aircraft]
Aircraftsystemindicationsshallbesimpletounderstandandread.
[REC-54] Aircraftsystemsshallbedesignedinawaythattheysupportthedecision-makingprocessratherthanimpairitbyanoverloadofdata.
TUGrazIMasterthesis
Results
74
[SC-63_Aircraft]
ProceduresofactivatingCAPSinlife-threateningsituationsshallbebroughttonoticeableattentioninthecabin.
[REC-55] Optionstoactivateapplicablepassivesafetyequipmentshallalwaysbeconsideredandmentionedinpersonalpilotbriefings.Appropriateindicationsbytheon-boardavionicssystemmayreducethetimeofpossiblestartleeffects.
Table3-1Safetyrecommendations
TUGrazIMasterthesis
Results
75
The existing accident report does not contain all necessary information to gain a holistic
understanding of the prevailing loss. Through the STAMP (Leveson, 2011) modeling subsequently
questionsemerged (refer toTable3-2Questions raised). Itsanswerswouldneed tobeconsidered
for further clarification in the CAST (Leveson, 2011) analysis and would probably involve revising
already-definedsafetyconstraintsandrecommendations.
Questionsraised
[QR-1] Arethereanyincidentsknowntotheauthorityinrespectoftheaccidentpilot?
[QR-2]Statedetailsabouttheinitialtrainingoftheaccidentpilotandherprogress(type/duration,typesofaircraft,detailsaboutdescentplanning,energymanagement,busyairportoperations,stabilizedapproachcriteria,stall/spinavoidance,CAPS)?
[QR-3] Whatwasthestatus/progressoftheaccidentpilot’sinstrumenttraining?
[QR-4] Whathadbeentheweaknessesoftheaccidentpilot,intheopinionoftheCFIs?
[QR-5] Wasgoodairmanshipinrespectofspinavoidance(asmentionedinthePOH)trained?
[QR-6] WastheFOMwiththe“EnvelopeofSafety”taughtaspartoftheinitialtrainingfortheCirrusaircraft?
[QR-7] DidthepilotattendanycoursesinSRMorrelatedtopicsandwhathadbeenthecontent?
[QR-8] Howwasthepilot’sattitudeinrespectofherownsafetyculture?
[QR-9] Wastheaccidentpilottrainedtorecognizelossofcontrolsituationsandhowtoescape?
[QR-10] WhichcommunicationprocessesattheHOUATCFacilityrequireimprovements?
[QR-11] WaspeerpressureinfluencingthecommunicationbetweentheATCtraineeandhisinstructor?
[QR-12] Whichalternativeprocedures(exceptvisualseparation)forre-aligningaircraftinthetrafficpatternwerecommon?
[QR-13] AretheATCcontrollerstrainedtofollowICAOstandardphraseologyandavoidunnecessarilylongATCclearances,especiallyduringcriticalphasesofflight?
[QR-14] DotheLCcontrollershaveadequatetrainingforvectoringaircraftinthenearproximityoftheairportunderhigh-trafficconditions?
[QR-15] WasLCcontroleverindoubt,thatN4252Gmightnotbeabletolandtheaircraftsuccessfully?
[QR-16] HowdoesanATCcontrollerevaluatetheconfidenceofpilots?
[QR-17] DidtheLCCanticipatethehighworkloadandstressthatthepilotofN4252Gwasunderatthethirdgo-around?
[QR-18] Howwasassured,thattheLCCtakingoverhadsufficientsituationalawarenessabouttheATCtrafficsituation?
[QR-19] HowisitassuredthatindividualproceduresandworkingpracticesaresharedamongeveryATCteammember?
[QR-20] HowwastheperformanceofATCcontrollersassured?
[QR-21] WhatschedulestheissueofnewPOHrevisions?
[QR-22] WhatisthealternativeprocedureforpilotsiftheCAPSsystemcannotbeactivatedincaseofanunintendedspin?
[QR-23] Wasthepilotawareoftheassociatedrisksdueartificialaerodynamicforcesonthecontrolyoke?
[QR-24] HowdoesthemanufacturerassurethatLOCisavoidedinCirrusaircraft?
[QR-25] DidtheaccidentpilotparticipateinanyCPPPtraining?
TUGrazIMasterthesis
Results
76
Questionsraised
[QR-26] DidtheaccidentpilotparticipateinanyCDMseminar?
[QR-27] DidanyofthepassengersparticipateinaPartnerinCommandseminar?
[QR-28] DidtheactualNOTAMsatthedayofaccidentstateanydeficienciesinfluencingthesafetyofflight(e.g.unserviceabilityofPAPI,displacedthresholds,etc.)?
[QR-29] Underwhichpre-requisitesdidtheoperator/aircraftownerpermitthepilottooperatetheaircraft?
[QR-30] Whatwastheoperator’s/aircraftowner’ssafetypolicy(requirements,currency,training)forpilotsoperatingtheaircraft?
[QR-31] Whatarethedetailsconcerningtheaccidentpilot’stypesofaircraftflown,flighthoursandlandings?
[QR-32] DidthepilothaveaflightplanningpackageincludingweatherforecastandNOTAMs?
[QR-33] Didtheaccidentpilotapplyanyriskassessmenttools?
[QR-34] Didthepilotwaitatleast24hoursaftertakingZolpidembeforeherflyingactivity(asrecommendedbytheFAA)?
[QR-35] Howdidthepilotpreparefortheflightandwhathadbeenthecontentsoftheflightplanningpackage?
[QR-36] Whatwasthepilot’sattitudeinrespectofriskassessment?
[QR-37] Didthepilotperformanytrainingflightsoraflightreviewbeforetheaccident?
[QR-38] Wasthepilot’slevelofsituationalawarenessimpairedbyanyreasonandcouldthepilotingeneralbedistractedeasilywhenperformingtasks?
[QR-39] WasthepilottrainedinSRM?
[QR-40] Hadthepilotbeensubjecttotimepressure(appointment)onthedayoftheaccident?
[QR-41] Didthepilotactivelyoperateonothertypesofaircraftintherecentpast?
[QR-42] Wasthepilotapplyingcorrecttrimprocedures?
[QR-43] ArethereanyRDMdataavailableregardingaircrafttrim?
[QR-44] Wasthepilotawareofpossiblevisualillusions?
[QR-45] Hadtherebeenanyincidentsbythepilotinrespectofunstabilizedapproachesatotherairports?
[QR-46] Wasthepilottrained/assessedforside-slipmaneuvers?
[QR-47] Whichchartshadbeenusedasreferencefornavigation?
[QR-48] Wasthepilotabletoreadthechartsproperly?
[QR-49] Whatwasthereasonforapplyingreducedpowersettingsforthego-around?
[QR-50] Wasthepre-flightcheckincl.stallwarningsystemcheckperformedproperly?
[QR-51] DidATCrecordanystallwarningsignalsonthetransmissiontapes?
[QR-52] DoestheRDMstoreanactivestallwarningtrigger?
[QR-53] DidthepilotperformanyCAPStraining?
[QR-54] Wereanyofthepassengersontheflightundertimepressure?
[QR-55] Wereanyofthepassengersknownforairsicknessorotherphysiologicaldeficiencies?
[QR-56] Hadpassengersbeenbriefedonsterilecabinprocedures?
[QR-57] Didthepassengersfrequentlyflywithsingle-enginepistonaircraftand/orhaveextensiveaviationknowledge?
TUGrazIMasterthesis
Results
77
Questionsraised
[QR-58] Hadthepassengersbeenbriefedaboutlife-threateningsituationsrequiringtheactivationofCAPS?
[QR-59] Wasthestallwarningsystemfunctionableontheaccidentflight?
[QR-60] Wasthepilotawareofaerodynamicaircraftreactionswhenapproachingstallconditions?
[QR-61] WasthereanyfailureoftheprimaryflightdisplaysloggedbytheRDM?
[QR-62] Didtheprimaryflightdisplayfailorgetinanunreadablecondition?
[QR-63] Didtheaccidentaircrafthavealternateindicationsoftheprimaryflightinformation(speed,altitude,attitude)?
[QR-64] Forwhichspeedwastheaircrafttrimmedbeforethefinalimpact?
Table3-2Questionsraised
Figure2-24summarizestheresults(unsafecontrolactions(UCA),safetyconstraints(SC),questions
raised(QR))categorizedfortheindividualcomponentsintheHCS.
Figure3-1Generalmodelofhierarchicalcontrolstructureincludingresults
Themodeling of the prevailing accident of N4252G emerged 34 unsafe control actions, 63 safety
constraints,64raisedquestionsand55safetyrecommendations.
TUGrazIMasterthesis
Discussion
78
4 DISCUSSION
The interaction ofmany factorswas crucial for this accident. The hierarchical control structure in
Chapter2.4visuallyillustratesthecomplexityofasystem-theoreticalaccidentinvestigation,whicha
linear simplification - as traditionally used inmany cases - cannot provide. The comparisonof the
results of the linear analysis (refer to F Appendix) against a STAMP/ CAST (Leveson, 2011) based
analysisclearlyshowsthedifferentresults.
The complexity in aviation is steadily increasing and the multitude of relevant terms (refer to A
Appendix)illustratesonlyafractionofthenecessaryexpertisethattoday’spilotsneed.Despitethe
constantlyimprovedtechnicalaids,aviationaccidentscontinuetohappen,althoughthesearerarely
givenpublicimportanceingeneralaviation.Thatwasalsooneofthereasonswhytheauthorchose
thisaccidentasatopicforthemasterthesis.
Theaircraftinthisaccidentwasflownintoanundesiredaircraftstate,whicheventuallycausedthe
loss. Referring to the official accident report, the question emerged concerning what aspects
contributed a pilotwithmore than 300 flight hours of type experience in just over 2 years being
involved in such an accident. The question of whether a flight review could have avoided the
accidentcannotbeclearlyanswered.
Despite the fact that the safety recommendations of this thesis include changes in standards and
regulations, the author believes that the safety of aviation is not solely governed by laws and
regulations.Anyonewhoisactivelyinvolvedinaviation-notonlypilots-mustbemadeawarethat
regulations are only the foundation upon which decisions must be continually built. “Good
airmanship”requiresmuchmorethancompliancewithlegalregulationsandtheavoidanceof“dirty
dozen”. It requiresa strongemphasisondiscipline tocontinuously improveskillsandpermanently
assessdecisionswiththeriskstofinallyexecutesafeflightoperations.
Theimplementationofsafetyrecommendations intostandards/ legal lawisoftenconsideredasan
unnecessary restriction. However, when it is recognized that every single aviation operator can
contributetoasaferaviation,itisultimatelyuptotheattitudeofindividualstoinspireotherstoact
safelyandmakeaviationsaferinthefuture.
Finally, the authorhopes that researchers andpractitioners in aviation accident investigations can
obtainvaluable insights fromthis researchmethodandfindings,andthat theuseofSTAMP/CAST
willbeestablishedasbestpracticeinaviationaccidentinvestigation.
TUGrazIMasterthesis
Conclusions
79
5 CONCLUSIONS
ThisthesisprovidesaninsightfulinvestigationofthisspecificaccidentbyapplyingLeveson’sSTAMP
model and CAST methodology (Leveson, 2011). Compared with a conventional method of
investigation,theinsightsgainedandlessonslearnedfromthisstudy,althoughonlylimitedsources
ofinformationhadbeenavailabletotheauthor,highlightthepotentialinapplyingSTAMPinmodern
accidentinvestigations.
The influences of individual components were analysed and described. It was emphasized that
complex,system-theoreticalmodelscanalsobejustifiedbymeansofshortandsimplestatements.
The large number of identified recommendations illustrates the existing potential for revising
procedures in aviation. The questions raised describe that the present aviation accident could be
investigatedandunderstoodinfurtherdetailbyansweringtheseopenquestions.
Theexistingaccidentreportwassubstantiatedbytheinvestigatingpartythroughcontributingfactors
butdidnotelaboraterecommendationsforpreventingfutureaircraftaccidents.Thehighercontrol
levels had influenced the outcome by a variety of contextual factors. It was not possible to
investigate indetail forwhatreasontheowneroftheaircraftpermittedtheoperationbythepilot
withoutavalidflightreview.Despitethehighworkloadandexternalinfluences,thepilotappliedhis
habits,whichheobviouslydidnotclassifyasunsafeandthereforecontinued.Similarly, itwasalso
not obvious to ATC that applied habits deviating from known procedures would limit safety.
Information from the training organisation was limited to statementsmade by two of the pilot’s
flight instructors and a number of questions remained unanswered. The extent to which the
manufacturer'sflightcontrolsystemtookeffectremainsquestionable,andtheextenttowhichCOPA
provided training courses to the pilot and passengers was not apparent due to the lack of
information. Restrictions fromHOU airport could not be researched. Finally,when aircraft control
waslost,thepassivesafetyaidCAPSwasnotactivated.
The assumption is confirmed that the accident was still favored by the interaction of individual
controllers.Thisconcludesthatregularadaptingtheaviationsystemisrequiredinsofarthatitdoes
notblamethemistakesofanindividual.Recommendationsaretobeimplementedtoensurethatin
the interaction of unsafe control actions under worst-case environmental conditions through
individualcomponents,theresultisnotanaccident.
TUGrazIMasterthesis
References
80
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TUGrazIMasterthesis
AAppendix
A-1
APPENDIXA
DefinitionofRelevantTerms
Inordertounderstandthetermsusedinthisthesis,thisappendixprovidesa listofdescriptionsof
themost common terms used. It is important to note that these terms and their definitions are
typicallynot self-explanatoryanddonothaveanyaccepteddictionarydefinitions, andhence they
areonlyapplicableinthedocumentinwhichtheyaredefined.
Accident.“Anoccurrenceassociatedwiththeoperationofanaircraftwhich,inthecaseofamanned
aircraft,takesplacebetweenthetimeanypersonboardstheaircraftwiththeintentionofflightuntil
suchtimeasallsuchpersonshavedisembarked,orinthecaseofanunmannedaircraft,takesplace
betweenthetimetheaircraftisreadytomovewiththepurposeofflightuntilsuchtimeasitcomes
torestattheendoftheflightandtheprimarypropulsionsystemisshutdown,inwhich:
a)apersonisfatallyorseriouslyinjuredasaresultof:
• beingintheaircraft,or
• direct contact with any part of the aircraft, including parts which have become detached
fromtheaircraft,or
• directexposuretojetblast,exceptwhentheinjuriesarefromnaturalcauses,self-inflictedor
inflictedbyotherpersons,orwhen the injuries are to stowawayshidingoutside theareas
normallyavailabletothepassengersandcrew;or
b)theaircraftsustainsdamageorstructuralfailurewhich:
• adverselyaffectsthestructuralstrength,performanceorflightcharacteristicsoftheaircraft,
and
• wouldnormallyrequiremajorrepairorreplacementoftheaffectedcomponent,exceptfor
engine failure or damage, when the damage is limited to a single engine (including its
cowlings or accessories), to propellers, wing tips, antennas, probes, vanes, tires, brakes,
wheels, fairings, panels, landing gear doors, windscreens, the aircraft skin (such as small
dents or puncture holes), or for minor damages to main rotor blades, tail rotor blades,
landinggear,andthoseresultingfromhailorbirdstrike(includingholesintheradome);or
c)theaircraftismissingoriscompletelyinaccessible.
Note1-Forstatisticaluniformityonly,aninjuryresultingindeathwithin30daysofthedateofthe
accidentisclassified,byICAO,asafatalinjury.
Note2-Anaircraftisconsideredtobemissingwhentheofficialsearchhasbeenterminatedandthe
wreckagehasnotbeenlocated”(ICAO,Annex13,2016,p.1-1).
TUGrazIMasterthesis
AAppendix
A-2
Airmanship. “Airmanship is the consistent use of good judgement and well-developed skills to
accomplishflightobjectives.Thisconsistencyisfoundedonacornerstoneofuncompromisingflight
discipline and is developed through systematic skill acquisition and proficiency. A high state of
situationalawarenesscompletestheairmanshippictureandisobtainedthroughknowledgeofone’s
self,aircraft,environment,teamandrisk”(Kern,1996,p.22).
Assertiveness. “Assertiveness is a communication and behavioral style that allows us to express
feelings,opinions,concerns,beliefsandneeds inapositiveandproductivemanner.[…]Beingboth
unabletoexpressourconcernsandnotallowingothertoexpresstheirconcernscreatesineffective
communications and damages teamwork. Unassertive teammembers can be forced to go with a
majoritydecision,evenwhentheybelieveitiswronganddangeroustodoso”
(Skybrary.aero,retrievedfrom
https://www.skybrary.aero/index.php/The_Human_Factors_%22Dirty_Dozen%22#Lack_of_assertive
ness,2019).
Causes.“Actions,omissions,events,conditions,oracombinationthereof,whichledtotheaccident
orincident.Theidentificationofcausesdoesnotimplytheassignmentoffaultorthedetermination
ofadministrative,civilorcriminalliability”(ICAO,Annex13,2016,p.1-2).
Control Structure. “A control structure captures functional relationships and interactions by
modelingthesystemasasetoffeedbackcontrolloops.Thecontrolstructureusuallybeginsatavery
abstract level and is iteratively refined to capturemore detail about the system” (Leveson, STPA
Handbook,2018,p.14).
DirtyDozen.“TheDirtyDozenrelatedtoaviationreferstotwelveofthemostcommonhumanerror
preconditions, or conditions that can act as precursors, to accidents or incidents. These twelve
elementsinfluencepeopletomakemistakes.[…]
• LackofCommunication:Poor communicationoftenappearsat the topof contributingand
causal factors in accident reports, and is therefore one of themost critical human factor
elements[…]
• Complacency:Complacencycanbedescribedasafeelingofself-satisfactionaccompaniedby
alossofawarenessofpotentialdangers[…]
• LackofKnowledge:[…]
• Distraction:Distractioncouldbeanythingthatdrawsaperson’sattentionawayfromthetask
[…]
TUGrazIMasterthesis
AAppendix
A-3
• LackofTeamwork:Inaviationmanytasksandoperationsareteamaffairs;nosingleperson
(ororganisation)canberesponsibleforthesafeoutcomesofalltasks.However,ifsomeone
isnotcontributingtotheteameffort,thiscanleadtounsafeoutcomes[...]
• Fatigue: Fatigue is a natural physiological reaction to prolonged physical and/ or mental
stress[…]
• LackofResources:[…]
• Pressure:Pressureistobeexpectedwhenworkinginadynamicenvironment.[…]Pressure
canbecreatedbylackofresources,especiallytime;andalsofromourowninabilitytocope
withasituation[...]
• LackofAssertiveness:[…]Assertivenessisacommunicationandbehavioralstylethatallows
us to express feelings, opinions, concerns, beliefs and needs in a positive and productive
manner[...]
• Stress:Therearemanytypesofstress.Typically in theaviationenvironmenttherearetwo
distincttypes-acuteandchronic.Acutestressarisesfromreal-timedemandsplacedonour
senses,mentalprocessingandphysicalbody;suchasdealingwithanemergency,orworking
under timepressurewith inadequate resources. Chronic stress is accumulated and results
from long-term demands placed on the physiology by life’s demands, such as family
relations,finances,illness,bereavement,divorce,orevenwinningthelottery[…]
• LackofAwareness:Workinginisolationandonlyconsideringone’sownresponsibilitiescan
lead to tunnel vision; a partial view, and a lack of awarenessof the affect our actions can
haveonothersandthewidertask.Suchlackofawarenessmayalsoresultfromotherhuman
factors,suchasstress,fatigue,pressureanddistraction[…]
• Norms:[…]ItisimportanttounderstandthatmostNormshavenotbeendesignedtomeet
allcircumstances,andthereforearenotadequatelytestedagainstpotentialthreats”
(Skybrary.aero,retrievedfrom
https://www.skybrary.aero/index.php/The_Human_Factors_%22Dirty_Dozen%22,2019).
FITS(FAAIndustryTrainingStandards).“FITSisfocusedontheredesignofgeneralaviationtraining.
Instead of training pilots to pass practical test, FITS focuses on expertly manage real-world
challenges.Scenariobasedtraining isusedtoenhancetheGApilots’aeronauticaldecisionmaking,
risk management, and single pilot resource management skills” (FAA.gov, retrieved from
https://www.faa.gov/training_testing/training/fits/more/,2019).
TUGrazIMasterthesis
AAppendix
A-4
Flight Review. “The purpose of the flight review required by [Title] 14 CFR part 61, § 61.56 is to
provide for a regular evaluation of pilot skills and aeronautical knowledge. Consequently, a flight
review isa routineevaluationofapilot’sability toconductsafe flight. Ineffect, it isaproficiency-
basedexerciseinwhichtheairmanisrequiredtodemonstratethesafeexerciseoftheprivilegesof
hisorherpilotcertificate.[…]theflightreviewisnotatestorcheckride,butratheratrainingevent
inwhichproficiencyisevaluated.[…]Under§61.56(c)nopersonmayactasPICofanaircraft,except
asprovided in§61.56(d), (e),and(g),unlesswithinthepreceding24calendar-monthsthatperson
hasaccomplishedasatisfactoryflightreviewinanaircraftforwhichthatpilotisappropriatelyrated.
Anauthorizedinstructororotherpersonapprovedmustconducttheflightreview.[…]apersonwho
hassatisfactorilycompletedoneormorephasesoftheFAA-sponsoredWINGSwithinthepreceding
24calendar-monthsdoesnotneedtoaccomplishtheflightreviewrequirementsofthissection.[…]
Pilotsandflightinstructorsshouldbeawarethat,under§61.56(d),thereisnorequirementforpilots
whohavecompletedcertainproficiencychecksandratingswithinthepreceding24calendar-months
to accomplish a separate flight review. [...] Before beginning the flight portion of the bi-annually
[biennially]requiredflightreview,theflightinstructorshoulddiscussvariousoperationalareaswith
the pilot. This oral review should include, but not be limited to, areas such as aircraft systems,
speeds, performance, meteorological and other hazards (e.g. wind shear and wake turbulence),
operations in controlled airspace, and abnormal and emergency procedures. The emphasis during
this discussion should be on practical knowledge of recommended procedures and regulatory
requirements. […] Regardless of the pilot’s experience, the flight instructor should review at least
those maneuvers considered critical to safe flight, such as: takeoffs, stabilized approaches to
landings, slow flight, stall recognition, stalls, and stall recovery, spin recognition and avoidance,
recovery fromunusualattitudesandoperating theaircraftby sole reference to instrumentsunder
actual or simulated conditions” (USDepartment of Transportation, AC 61-98D (supersedes AC 61-
98C),2018,p.4-1,4-2,4-6,4-7).
GeneralAviationOperation.“Anaircraftoperationotherthanacommercialairtransportoperation
oranaerialworkoperation”(ICAO,Annex6,PartII,2016,p.1.1-4).
Hazard.“Ahazardisasystemstateorsetofconditionsthat,togetherwithaparticularsetofworst-
caseenvironmentalconditions,willleadtoaloss”(Leveson,STPAHandbook,2018,p.17).
TUGrazIMasterthesis
AAppendix
A-5
IMSAFE. “One of the best ways single pilots can mitigate risk is to use the IMSAFE checklist to
determinephysicalandmentalreadinessforflying.[...]IMSAFE,whichstandsforIllness,Medication,
Stress, Alcohol, Fatigue, and Emotion“ (US Department of Transportation, Pilot’s Handbook of
AeronauticalKnowledge,2016,p.2-8,17-18).
Investigation. “A process conducted for the purpose of accident prevention which includes the
gathering and analysis of information, the drawing of conclusions, including the determination of
causesand/orcontributingfactorsand,whenappropriate,themakingofsafetyrecommendations”
(ICAO,Annex13,2016,p.1-2).
Loss.“Alossinvolvessomethingofvaluetostakeholders.Lossesmayincludealossofhumanlifeor
humaninjury,propertydamage,environmentalpollution,lossofmission,lossofreputation,lossor
leakof sensitive information,oranyother loss that isunacceptable to thestakeholders” (Leveson,
STPAHandbook,2018,p.16).
LossofControl.“LOCreferstoaircraftaccidentsthatresult fromsituations inwhichapilotshould
havemaintained(orshouldhaveregained)aircraftcontrol,but failedtodoso”(USDepartmentof
Transportation,AC61-98D(supersedesAC61-98C),2018,p.2-1).
Notices to Airmen (NOTAMs). “Notices to Airmen, or NOTAMs, are time-critical aeronautical
informationeithertemporaryinnatureornotsufficientlyknowninadvancetopermitpublicationon
aeronautical charts or in other operational publications. The information receives immediate
disseminationviatheNationalNoticetoAirmen(NOTAM)System.NOTAMscontaincurrentnotices
toairmenthatareconsideredessentialtothesafetyofflight,aswellassupplementaldataaffecting
otheroperationalpublications”(USDepartmentofTransportation,Pilot’sHandbookofAeronautical
Knowledge,2016,p.1-12).
PAVE checklist. “By incorporating the PAVE checklist into preflight planning, the pilot divides the
risks of flight into four categories: Pilot-in-command (PIC), Aircraft, enVironment, and External
pressures (PAVE) which form part of a pilot’s decision-making process” (US Department of
Transportation,Pilot’sHandbookofAeronauticalKnowledge,2016,p.2-8).
TUGrazIMasterthesis
AAppendix
A-6
Pilot’s Operating Handbook/ Airplane Flight Manual (POH/ AFM)16. “FAA-approved documents
publishedbytheairframemanufacturer that list theoperatingconditions foraparticularmodelof
aircraft” (USDepartment of Transportation, Pilot’sHandbookof Aeronautical Knowledge, 2016, p.
G23).
PilotinCommand(PIC).“Thepilotdesignatedbytheoperator,orinthecaseofgeneralaviation,the
owner,asbeingincommandandchargedwiththesafeconductofaflight”(ICAO,Annex2,2005,p.
1-7).TheCodeofFederalRegulationsdeclares that“thepilot incommandofanaircraft isdirectly
responsible for, and is the final authority as to, the operation of that aircraft. […] In an in-flight
emergencyrequiringimmediateaction,thepilotincommandmaydeviatefromanyruleofthispart
totheextentrequiredtomeetthatemergency” (rf.Title14oftheCodeofFederalRegulations(14
CFR)part91,§91.3).
PrecisionApproachPathIndicator(PAPI).ReferringtotheAIM(2017)aPAPI isdefinedasavisual
aid of one row of lights in two- or four-light systems arranged to provide descent guidance
informationduringtheapproachtotherunway.Apilotonthecorrectglideslopewillseetwowhite
lights and two red lights (rf. (USDepartment of Transportation, Aeronautical InformationManual,
2017,p.2-1-1,2-1-4)).
Safety constraint. “A system-level safety constraint specifies system conditions or behaviors that
needtobesatisfiedtopreventhazards(andultimatelyprevent losses)” (Leveson,STPAHandbook,
2018,p.20).
Safety recommendation. “A proposal of an accident investigation authority based on information
derived from an investigation, made with the intention of preventing accidents or incidents and
which innocasehasthepurposeofcreatingapresumptionofblameor liabilityforanaccidentor
incident. In addition to safety recommendations arising from accident and incident investigations,
safetyrecommendationsmayresultfromdiversesources,includingsafetystudies”(ICAO,Annex19,
2013,p.1-3).
Safety risk. “Thepredictedprobabilityandseverityof theconsequencesoroutcomesofahazard”
(ICAO,Annex19,2013,p.1-3).
16Title14 of the Code of Federal Regulations (14 CFR) part 91, §91.9 requires that pilots comply with theoperatinglimitationsspecifiedintheapprovedflightmanuals,markings,andplacards.
TUGrazIMasterthesis
AAppendix
A-7
Single-PilotResourceManagement(SRM).“Itistheabilitytomanagealltheresourcesavailabletoa
singlepilottoensurethatthesuccessfuloutcomeoftheflightisneverindoubt”(FOM-SR20,2011,p.
3-2).
SituationalAwareness (SA).ReferringtoEndsley (2000),situationalawareness is theperceptionof
elementsintheenvironmentwithinavolumeoftimeandspace,thecomprehensionoftheirmeaning
andtheprojectionoftheirstatusinthenearfuture17.SAisthereal-worldchangingknowledgethatis
critical foreffectivedecision-makingandaction.TheformaldefinitionofSAbreaksdown intothree
separatelevels:
Level1–perceptionofelementsintheenvironment18
Level2–comprehensionofthecurrentsituation19
Level3–projectionoffuturestatus
(rf.(Endsley,SituationAwarenessAnalysisandMeasurement,2000,p.13-14)).
StabilizedApproachCriteria.“[…]theairplaneshouldbestabilizedby500ftaboveairportelevation
during straight-in approaches in visual meteorological conditions (VMC). Pilots should monitor at
leastsevenmajorelementsthatdefineastabilizedapproachinaGAairplane.TheFAAconsidersan
approach to touchdowntobestabilizedwhentheairplanemeetsallof the followingcriteria,with
onlyminordeviations:
[…]Glidepath.Theairplane ison thecorrect flightpath.Typically, theglidepath is3degrees to the
runwaytouchdownzone(TDZ)(obstructionspermitting).
[…]Heading.Theairplaneistrackingtheextendedcenterlinetotherunwaywithonlyminorheading/
pitchchangesnecessarytocorrectforwindorturbulencetomaintainalignment.Bankangleshould
notexceed15degreesonfinalapproach.
[…] Airspeed. The pilotmaintains a constant target airspeedwithin +10/ -5 kts indicated airspeed
(KIAS),whichisusuallyat,butnolowerthan,therecommendedlandingspeedspecifiedinthePOH
[…] Note: […] Pilots generally select an appropriate approach speed for the prevailing weather,
aircraft,traffic,andperformanceconditions,butnotlessthan1.3Vs0.However,aircraftareusually
slowedtoanormallandingspeedwhenonthefinalapproachjustpriortolanding.
17pilotsusuallycallitto“stayaheadoftheaircraft”18influencesmay be channelized attention (tunnel vision), distraction and task saturation (rf. (Kern, 1996, p.234))19newpilotsmighthavedifficultiesdevelopingSAatthislevelorbeyond,astheyhavefewexperientialpatternsonwhichtoplacenewinformationofevents(rf.(Kern,1996,p.236))
TUGrazIMasterthesis
AAppendix
A-8
[…]Configuration.Theairplaneisinthecorrectlandingconfigurationwithflapsasrequired,landing
gearextended,andtheairplaneintrim.
[…]RateofDescent.Descentrateisaconstantandgenerallynogreaterthan500fpm.Ifadescent
greaterthan500fpmisrequiredduetoapproachconsiderations,itshouldbereducedpriorto300ft
abovegroundlevel(AGL)andwellbeforethelandingflareandtouchdownphase.
[…]PowerSetting.Powersetting isappropriatefortheairplaneconfigurationand isnotbelowthe
minimumpowerforapproachasdefinedbythePOH/AFM.
[…] Checklists/ Briefings. All briefings and checklists (except the landing checklist) are completed
priortoinitiatingtheapproach.
Note:ForatypicalGApistonairplaneinatrafficpattern,iftheapproachbecomesunstabilizedbelow
300ftAGL,thepilotshouldinitiateanimmediatego-around”(USDepartmentofTransportation,AC
61-98D(supersedesAC61-98C),2018,p.2-3,2-4).
StartleEffect.“Inaviation,startleeffectcanbedefinedasanuncontrollable,automaticreflexthatis
elicitedbyexposure toa sudden, intenseevent thatviolatesapilot’sexpectations. […]The startle
effectincludesboththephysicalandmentalresponsestoasuddenunexpectedstimulus.Whilethe
physicalresponsesareautomaticandvirtually instantaneous,thementalresponses-theconscious
processing and evaluation of the sensory information - can bemuch slower. In fact, the ability to
process the sensory information - to evaluate the situation and take appropriate action - can be
seriouslyimpairedorevenoverwhelmedbytheintensephysiologicalresponses.[…]performanceof
more complexmotor tasksmaybe impacted forup to10 seconds” (Skybrary.aero, retrieved from
https://www.skybrary.aero/index.php/Startle_Effect,2019).
System.“Asetofthings(referredtoassystemcomponents)thatacttogetherasawholetoachieve
somecommongoal,objective,orend”(Leveson,STPAHandbook,2018,p.169).
TAA.“TechnologicallyAdvancedAircraft(TAA)areequippedwithnew-generationavionicsthattake
full advantage of computing power and modern navigational aids to improve pilot situational
awareness, system redundancy and dependence on equipment, and to improve in-cockpit
informationabout traffic,weather, airspaceand terrain” (AOPATechnologicallyAdvancedAircraft,
2007,p.2).
Traffic Pattern. A visual traffic pattern is amaneuver flown by aircraft taking-off or landingwhile
maintaining visual contact with the airfield. It comprises crosswind, downwind, base and final-leg
elements.
TUGrazIMasterthesis
AAppendix
A-9
Unsafe Control Action. “An Unsafe Control Action (UCA) is a control action that, in a particular
contextandworst-caseenvironment,willleadtoahazard”(Leveson,STPAHandbook,2018,p.35).
Vigilance. “Vigilance is a term that refers to an individual’s ability to pay close and continuous
attentiontoafieldofstimulationforaperiodoftimeandbeingwatchfulforanyparticularchanging
circumstances”
(Skybrary.aero,retrievedfromhttps://www.skybrary.aero/index.php/Vigilance_in_ATM,2019).
Wake turbulence. “When an airplane generates lift, air spills over the wingtips from the high
pressure areas below the wings to the low pressure areas above them. This flow causes rapidly
rotating whirlpools of air called wingtip vortices or wake turbulence” (US Department of
Transportation,Pilot’sHandbookofAeronauticalKnowledge,2016,p.G34).
WINGS.“TheobjectiveoftheWINGS-PilotProficiencyProgramistoreducethenumberofaccidents
inGeneralAviation(GA)byassistingairmentofindeducationalopportunitiesdesignedtohelpthem
apply the principles of risk assessment and riskmanagement (RM).When properly applied, these
principles will help mitigate accident causal factors associated with common pilot errors, lack of
proficiency, and faulty knowledge. The Federal Aviation Administration’s (FAA) purpose is to
encouragethemajorityofGApilots,throughWINGS,toengageinongoing,targetedflyingtasksand
learning activities keyed to identified risks and which are designed to mitigate those risks” (US
DepartmentofTransportation,AC61-91J,2011,p.1).
TUGrazIMasterthesis
BAppendix
B-1
APPENDIXB
LossofControlinGeneralAviation
“While maneuvering an airplane at low altitude in visual meteorological conditions (VMC), many
pilotsfail20
• toavoidconditionsthatleadtoanaerodynamicstall,
• torecognizethewarningsignsofastallonset,and
• toapplyappropriaterecoverytechniques.
Many stall accidents that occur in VMC result when a pilot is momentarily distracted from the
primarytaskofflying,suchaswhilemaneuveringintheairporttrafficpattern,duringanemergency,
orwhenfixatingongroundobjects.Aerodynamicstallaccidentsfallintothe“lossofcontrolinflight”
category“(NTSB,SafetyAlert019,2013,p.1).
“TheGAJSCcitesLOCasoneofthesixmostcriticalandcommoncausesofGAaccidents.[…]TheFAA
remindspilotsandflightinstructorstoregularlyevaluate(andelevate)proceduresandskillstoavoid,
recognize, and recover from emergencies such as LOC. […] LOC usually occurs when pilots lack
proficiency.Conditionsexceedingpersonal skill limitationscanpresent themselvesatany timeand
can occur unexpectedly. In this event, the pilot should be able to avoid being startled, make
appropriatedecisionsinatimelymanner,andbeabletoexerciseskillsataproficiencylevelheorshe
may not have maintained or attained since acquired during initial training. This makes personal
currencyprogramsandproficiencytrainingessential. […]LOCaccidentsoftenoccurwhilepilotsare
maneuveringat lowaltitudeandairspeed,suchas inanairport trafficpattern” (USDepartmentof
Transportation,AC61-98D(supersedesAC61-98C),2018,p.2-1,2-2).
20Author’s note: “fail“ in respect of humans focuses on blame, which contradicts systemic analyses of whyhumanerrorsappearedtoberightatthetimetheyhadoccured
TUGrazIMasterthesis
CAppendix
C-1
APPENDIXC
GeneralInformationaboutSTAMP
“Forcenturiescomplexityhasbeenhandledbytraditionalmethodsbreakingthesystemintosmaller
components,examiningandanalysingeachcomponentinisolation,andthencombiningtheresults
inorder tounderstandthebehaviorof thecomposedcomponents. […]Thesuccessof this typeof
decompositional or reductionist approach relies on the assumption that the separation and
individual analysis does not distort the phenomenon or property of interest. […] Complexity is
creating“unknowns”thatcannotbeidentifiedbybreakingthesystembehaviorintochainsofevents.
Inaddition,complexityisleadingtoimportantsystemproperties(suchassafety)notbeingrelatedto
thebehaviorofindividualsystemcomponentsbutrathertotheinteractionsamongthecomponents.
Accidentscanoccurduetounsafeinteractionsamongcomponentsthathavenotfailedand,infact,
satisfy their requirements. […] STAMP (System-Theoretic Accident Model and Processes) is an
accident causalitymodelbasedon systems theory. […]Systems theorywasdevelopedafterWorld
War II to copewith the increasingly complex systemswith advanced technology that were being
created.[…]
Someuniqueaspectsofsystemstheoryare:
• Thesystemistreatedasawhole,notasthesumofitsparts.[…]
• A primary concern is emergent properties, which are properties that are not in the
summation of the individual components but “emerge” when the components interact.
Emergentpropertiescanonlybetreatedadequatelybytakingintoaccountalltheirtechnical
andsocialaspects.
• Emergentpropertiesarisefromrelationshipsamongthepartsofthesystem,thatis,byhow
theyinteractandfittogether.[…]
It expands the traditional model of causality beyond a chain of directly-related failure events or
component failures to include more complex processes and unsafe interactions among system
components, […].The twomostwidelyusedSTAMP-basedtools todayareSTPA (System-Theoretic
ProcessAnalysis)andCAST(CausalAnalysisbasedonSTAMP).STPAisapro-activeanalysismethod
thatanalysesthepotentialcauseofaccidentsduringdevelopmentsothathazardscanbeeliminated
or controlled. CAST is a retroactive analysismethod that examines an accident/ incident that has
occurredandidentifiesthecausalfactorsthatwereinvolved”(Leveson,STPAHandbook,2018,p.5,
7,4,10,12,13).
“CASTcanbeusedto identifythequestionsthatneedtobeansweredtofullyunderstandwhythe
accident occurred. It provides the basis formaximizing learning from the events. The use of CAST
TUGrazIMasterthesis
CAppendix
C-2
does not lead to identifying single causal factors or variables. Instead it provides the ability to
examine the entire sociotechnical system design to identify theweaknesses in the existing safety
controlstructureandtoidentifychangesthatwillnotsimplyeliminatesymptomsbutpotentiallyall
thecausalfactors,includingthesystemicones.OnegoalofCASTistogetawayfromassigningblame
andinsteadtoshiftthefocustowhytheaccidentoccurredandhowtopreventsimilarlossesinthe
future.Toaccomplishthisgoal, it isnecessarytominimizehindsightbiasand insteadtodetermine
why people behaved the way they did, given the information they had at the time” (Leveson,
EngineeringaSaferWorld,2011,p.349).
“STPAandSTAMPwerefoundtobemoreefficientandeffectivethantraditionalmethods,butthey
canbecombinedwithtraditionalmethods,too.[…]Theyhaveasolidtheoreticalbackgroundanda
practicalapplicabilitytocomplexproblems”(Koglbauer,2018,p.131-133).
HierarchicalControlStructure(HCS)inSTAMP
ReferringtoLevesson(2018),aHCScomprisesoverlappingandinteractingcontrolloops,whichhelp
tomanagethecomplexity.Thisisoneofthemaininvestigationsineveryhazardanalysis.Ingeneral,
a controller may provide control actions to control some process and enforce constraints on the
behavior of the controlled process. The control algorithms (also called operating procedures or
decision-making rules) determine the control actions to provide. Controllers have process models
(also called mental models) that represent the human controller’s internal beliefs used to make
decisions. Processmodelsmay include beliefs about the process being controlled or other relevant
aspects of the system or the environment, and theymay be updated in part by feedback used to
observethecontrolledprocess(rf.(Leveson,STPAHandbook,2018,p.22,23)).
Leveson(2011)describesthatapplyingtheCASTanalysismethodentailsunderstandingthedynamic
processthatledtotheloss.Theaccidentprocessisdocumentedbyshowingthesociotechnicalsafety
controlstructureforthesysteminvolvedandthesafetyconstraintsthatwereviolatedateachlevelof
thiscontrolstructure,aswellaswhy.Theanalysisresultsinmultipleviewsoftheaccident,depending
ontheperspectiveandlevelfromwhichthelossisbeingviewed.Movingupthelevelsofthesafety
control structure determines how and why each successive higher level in the control structure
allowedorcontributedtotheinadequatecontrolatthecurrentlevel(rf.(Leveson,EngineeringaSafer
World,2011,p.350,351)).
TUGrazIMasterthesis
DAppendix
D-1
APPENDIXDIn this appendix, the author collects and summarizes essential information and data from various
availabledocumentsaboutthebasiceventsoftheflightN4252G.Itsknowledgeandunderstandingis
relevantforthemodelingoftheaccidentbasedonSTAMP(Leveson,2011).
HistoryofFlightN4252G
“OnJune9,2016,about13:09centraldaylight time,aCirrusSR20single-engineairplane,N4252G,
wassubstantiallydamagedafteritimpactedterrainfollowingalossofcontrolduringinitialclimbat
theWilliam P. Hobby Airport (HOU), Houston, Texas” (NTSB, Cockpit Display(s) - Recorded Flight
Data, 2017, p. 1). “Witnesses saw the airplane at a low altitude when it turned to the left and
descended.A security camera video showed that the airplane spun to the left andwas about 45°
nosedowninaslightly left-wing-lowattitudebefore impactwithterrain.Theairplaneimpactedan
unoccupied automobile in a hardware store parking lot about half-mile north of runway 35. The
video showed that the airplane’s airframe parachute rocket motor activated during the impact;
however, the parachute remained stowed in the empennage and did not deploy” (NTSB, Aviation
AccidentFinalReport,2017,p.4).“Theprivatepilotandthetwopassengerswerefatallyinjured.The
airplanewasregisteredandoperated[…]undertheprovisionsof14CodeofFederalRegulationsPart
91asapersonalflight.Visualmeteorologicalconditionsprevailedandavisualflightrules(VFR)flight
planhadbeenfiled.TheairplanedepartedfromUniversityofOklahomaWestheimerAirport(OUN),
Norman,Oklahoma[…]andwasdestinedforHOU”(NTSB,CockpitDisplay(s)-RecordedFlightData,
2017,p.1).
TUGrazIMasterthesis
DAppendix
D-2
SummaryofBasicEventsofFlightN4252G
Factualaccident informationretrievedfromtheNTSBAviationAccidentFinalReport,2017andthe
HOUTowerAccidentPackageN4252G,2018arelistedasfollows:
Destination: HOU,Texas/USA
Dateandtime: June09,2016,13:09localtime(CDT)
Aircraft: CIRRUSDESIGNCORPSR20
Airframetotaltime21: 429hours,42hourssincelastinspection(January16,2016)
Avionics22: GarminG1000IntegratedFlightDeckwithRDM
Definingevent: Lossofcontrolinflight
Registration: N4252G
Serialnumber: 2217
Aircraftdamage: substantial
Personsonboard: 1pilot(female,age46),2passengers
Injuries: 3fatal
NTSBnumber: CEN16FA211
Positionofsun: Solarpositionatdate/timeofaccidentwasazimuth/elevation158°/83°
(rf.(NTSB,AviationAccidentFinalReport,2017,p.1-10),(HOU-ATCT-0064,2018,p.40)).
Thefollowingdatawereresearchedandsummarizedbytheauthor:
Runwaysinuse23: Runway4,LDA6000ftx150ft,4-LightPAPI(3.0°),thresholdelevation42ft
Runway35,LDA7602ftx150ft,4-LightPAPI(3.0°),thresholdelevation43ft
Weather24: At09:53CDT(approximatedeparturetime),visibility10miles,lowestclouds
werescatteredat2400ftAGL,brokenat18000ftAGL,winddirection070°
with8kts,temperature30°C,dewpoint23°C,AltimeterSetting29.95inches
Hg,noprecipitation;
At 12:53CDT (approximate accident time), visibility 10miles, lowest clouds
werebrokenat3600ftAGL,winddirection100°withspeeds/gusts12/16
21atthetimeofaccident22Electronicsystemsusedonaircraft.23Runwaydatawereretrievedfromhttps://www.airnav.com/airport/KHOUandverifiedwiththeHOUTowerAccident Package (HOU-ATCT-0064 2018, p. 40). Restrictions on LDA and serviceability of PAPI could not beverified,astheNTSBFinalReportandtheavailableNTSBDMSdocumentsoftheN4252GaccidentdonotstateNOTAMsandgeneralservicabilitiesatHOUatthetimeofaccident.24ObservedatHOUairport,1NMdistantfromaccidentsite.Source:WeatherSummaryFile(p.1)asretrievedfromNTSBDMSWebsite:https://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=60618&CFID=2395938&CFTOKEN=81732fd00bba5423-5AB1BC7B-CB39-E91F-3732EB517FD2FBDB
TUGrazIMasterthesis
DAppendix
D-3
kts,temperature32°C,dewpoint22°C,AltimeterSetting29.94inchesHg,no
precipitation;
Availableweatherforecastsonthedayofaccidentarenotmentionedinthe
officialNTSBaccidentreportanditsaccompanyingdocuments.
Massandbalance25: Themassandbalanceenvelopewasrecalculatedbytheauthorforthetime
of takeoff and impact. The results showed that the center of gravity was
withinsafelimits26forthewholeprogressofflight.
Flightpreparation: TherewasnoinformationmentionedintheofficialNTSBaccidentreportand
its accompanying documents regarding details of the flight preparation
packagefromthepilot.
Remainingfuel27: leftwingtank:13US-gal,rightwingtank:8.8US-gal
(equalsaremainingendurance28ofapproximately2hours)
Max.glideratio29: 9:1(equals6.34°)withbestglidespeed
25Author’snote:Astheactualbasic-empty-massofN4252Gwasnotavailableintheprevailingdocuments,theauthorappliedthebasic-empty-mass/-momentdataofasimilarSR20aircraft(2144lbs/303561lbs-inch)fortherecalculation.Forpilotandpassengersthefollowingnumberswereused:femalepilotwith155lbs,twomalepassengerswith175lbseach(oneofthemoccupyingthefrontseat).Theamountofcarriedbaggagecouldnotbeconfirmed.Therefore,twocalculationswithandwithoutanassumedtotalbaggagemassof65lbswereconsidered.Fuelonboard(28US-galinboththeleftandrightwingtankfortakeoff;13US-galintheleftand8.8US-galintheright wing tank before the impact) was considered as retrieved from the stored onboard data record(Attachment1-CockpitDisplaysFactualReport.csv)fromNTSBDMSwebsite:https://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=60618&CFID=2395938&CFTOKEN=81732fd00bba5423-5AB1BC7B-CB39-E91F-3732EB517FD2FBDB26FordetailsregardingsafeloadinglimitsrefertoPOH-SR20(2015),Section6,WeightandBalanceData.27Retrievedby theauthor fromthe laststoredonboarddatarecordbefore the impactat13:09:02CDT fromNTSBDMSwebsite:https://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=60618&CFID=2395938&CFTOKEN=81732fd00bba5423-5AB1BC7B-CB39-E91F-3732EB517FD2FBDB28Recalculated by the authorwith POH-SR20 2015, Section5, Range Endurance Profile for 65% Power (FuelFlow10,5US-galperhour).29RetrievedbytheauthorfromPOH-SR20,2015,Section3,ChapterEmergencyDescent,p.3-14.
TUGrazIMasterthesis
DAppendix
D-4
Pilot-Information
This section lists factual pilot information retrieved from the NTSB Aviation Accident Final Report
(2017):
Pilot: Female,age46
PilotLicense: PrivatePilotCertificate (single engine land)was receivedonMay2,
2014,nootherratings30
Medicalcertification: Class3withoutwaivers/limitations,
lastFAAmedicalexamOctober10,2014
Pilothours: 332.6hours (Total, all aircraft), 303.6hours (Total, this make and
model), 253hours (Pilot In Command, all aircraft), 28hours (Last
90days,allaircraft),7hours(Last30days,allaircraft),0hours(Last
24hours,allaircraft)
Pilot’sairportexperience: According to the logbook, shehad landedwithin class-Bairspaceat
least four times. Her most recent flight in class-B airspace was to
DallasLoveField (DAL),Dallas,Texas,andconsistedofa landingon
May30,2016,andatakeoffonJune3,2016.Therewasnoevidence
thatshehadflowntoHOUbeforetheaccidentflight.
Flightreview: HerlastflightrevieworequivalentwasonMay2,2014.
Interviewswiththepilot’sflightinstructorsandreviewofherlogbook
didnot findevidence that thepilothadcompleteda flight review in
theprevious24calendarmonths,asrequiredby14CFR61.56(c).31
Pathologicalinformation: An autopsy on the pilot was performed. The cause of death was
multipleblunt force injuries, and themannerofdeathwas ruledan
accident. Forensic toxicology on specimens from the pilot detected
thefollowingsubstances:Ibuprofen,Naproxen,Zolpidem.
TheuseofIbuprofenandNaproxenwouldgenerallynotpresentahazardtoaviationsafety.Zolpidem
isaprescriptionmedicationused to treat insomniaandmay impairmentaland/orphysicalability
required for the performance of potentially hazardous tasks, such as driving, flying and operating
heavymachinery.Due toadverse sideeffects, theFAA recommendswaitingat least24hoursafter
useofZolpidembeforeflying(rf.(NTSB,AviationAccidentFinalReport,2017,p.5,8)). 30Ratingsinthiscontextmeansotheraircraftratings,instrumentratings(IFR)orinstructorratings.31Title 14 CFR part 61.56(c) states thata personmay not act as pilot-in-command of an aircraft unless thatpersonhasaccomplishedasatisfactoryflightreviewwithinthepreceding24calendarmonths.
TUGrazIMasterthesis
DAppendix
D-5
Pilot-ExperienceLevel
Theon-typeandgeneralexperienceoftheaccidentpilotgainedinarelativelyshorttimeofjustover
two years, as mentioned previously, provides the impression of a well-experienced pilot. For the
process of modeling the prevailing accident in STAMP (Leveson, 2011), the author decided to
determine the Pilot’s Capability Category in reference to the pilot’s experience according to the
Envelope of Safety provided by the aircraft manufacturer Cirrus in its FOM-SR20 (2011) and
summarized in L Appendix, Figure 6-2Guidance for establishing PersonalWeatherMinimums and
Figure6-3EnvelopeofSafety.Thegrading (total ratingpointsaddedup:27) for theaccidentpilot
wascalculatedbytheauthoranticipatingthefollowingfacts:2-5yearsactivelyflying(3points),last
training >24months (5points), private pilot certificate (4points), total time <500hours (5points),
exact number of hours logged in the last 12months not documented (therefore, anticipated as
4points), 28hours in Cirrus in the last 90days (3points), no pilot mishap (0points), and Cirrus
Landingsduringthe last30daysnotdocumented(therefore,anticipatedas3points).Therewasno
documentation found concerning whether the pilot had successfully completed a Cirrus Transition
Training(rf.(FOM-SR20,2011,p.2-6)).
ItconcludedtodefinethePilot’sCapabilityCategoryoftheaccidentpilotas“infrequentflyer”.
In respect of thedefinedPilot’s CapabilityCategory, the aircraftmanufacturerCirrus recommends
thefollowingPersonalWeatherMinimums(fordetails,refertoLAppendix,Figure6-2Guidancefor
establishingPersonalWeatherMinimums).
windlimit15kts,x-windlimit5kts,maximumgust5kts
TUGrazIMasterthesis
EAppendix
E-1
APPENDIXEIn this appendix, the author summarizes the most relevant aspects of the SR20 Pilot Operating
Handbook (POH) and the SR20 Flight Operations Manual (FOM) for modeling the accident with
STAMP(Leveson,2011).
RelevantAspects-SR20PilotOperatingHandbook(POH)
A1was theactual revisionnumber (revisedDecember29,2015)at the timeof theaccidentand it
wasstillunrevisedandvalidatthetimeofpublicationofthisthesis:
POH,Section2– Limitations describes that theaircraft is certified in thenormal categoryandnot
designed for aerobatic operations.Only those operations incidental to normal flight are approved.
Theseoperationsincludenormalstalls,chandelles,lazyeights,andturnsinwhichtheangleofbankis
limitedto60°.Aerobaticmaneuversandspinsareprohibited.
ThemaximumflapextendedspeedVfeisthehighestspeedpermissiblewithwingflapsextended,itis
limited to 119 KIAS for Flaps 50%, and 104 KIAS for Flaps 100%. Themaximum structural cruising
speedVnoisthespeedthatshouldnotbeexceededexceptinsmoothair,andthenonlywithcaution.
Thenever-exceedspeedVneof200KIASisthespeedlimitthatmaynotbeexceededatanytime.
The airspeed indications are marked as follows: WHITE-arc32 - 61-104 KIAS - Full Flap Operating
Range,GREEN-arc33 -69-163KIAS -NormalOperatingRange,YELLOW-arc34 -CautionRange-163-
200KIAS,REDline35-200KIAS-Never-exceedspeed(rf.(POH-SR20,2015,p.2-11,2-4,2-5)).
POH, Section 3 – Emergency Procedures warns that in all cases if the aircraft enters an unusual
attitude followingor inconnectionwithastall,aspinconditionshouldbeassumedand immediate
deploymentof theCAPS is required.Underno circumstances should spin recoveryother thanCAPS
deployment be attempted. The aircraft is not approved for spins and has not been certified for
traditional spin recovery characteristics. The only approved and demonstrated method of spin
recovery is the activation of the CAPS. Accordingly, if the aircraft enters a spin, CAPS must be
deployed immediately.While the stall characteristics of the aircraftmake inadvertent entry into a
32“[The] lower limit is the most adverse stall speed in the landing configuration. [The] upper limit is themaximumspeedpermissiblewithflapsextended”(POH-SR2029.12.2015,p.2-5). 33“[The] lower limit is themaximumweightstall speedatmost forwardCGwithflaps retracted. [The]upperlimitisthemaximumstructuralcruisingspeed”(POH-SR2029.12.2015,p.2-5). 34“Operationsmustbeconductedwithcautionandonlyinsmoothair”(POH-SR2029.12.2015,p.2-5). 35“Maximumspeedforalloperations”(POH-SR2029.12.2015,p.2-5).
TUGrazIMasterthesis
EAppendix
E-2
spinextremelyunlikely,it ispossible.Spinentrycanbeavoidedbyusinggoodairmanship,including
coordinateduseofcontrols in turns,properairspeedcontrol following the recommendationsof the
POH, and never abusing the flight controls with accelerated inputs when close to the stall. If the
controls are misapplied and abused aggressive inputs are made to the elevator, rudder and/ or
aileronsatthestall,anabruptwingdropmaybefeltandaspinmaybeentered.
The CAPS should also be used in other life-threatening emergencies where CAPS deployment is
determined to be safer than continued flight and landing. Several possible scenarios in which the
activation of the CAPS would be appropriate include mid-air collisions, structural failures, loss of
control,landingininhospitableterrainandpilotincapacitation(rf.(POH-SR20,2015,p.3-28,3-33,3-
34)).
POH,Section4–NormalProceduresadvisesthatnormallandingsaretobemadewithfullflapswith
poweronoroff.Thespeedsforlandingapproachareasfollows:NormalApproachFlaps-Up88KIAS,
NormalApproach-Flaps50%83KIAS,NormalApproach-Flaps100%78KIAS.TheGo-AroundSpeed
with Flaps 50% is 78 KIAS. Surface winds and air turbulence are usually the primary factors in
determiningthemostcomfortableapproachspeeds.
Crosswind landings are made with full flaps and prolonged slips to be avoided. The maximum
allowable crosswind velocity is dependent upon the pilot capability as well as aircraft limitations.
Operationindirectcrosswindsof20ktshasbeendemonstrated.
Theprocedures for balked landings (go-arounds) state to climb, disengage theautopilot, apply full
power,andthenreducetheflapsettingto50%.Ifobstaclesmustbeclearedduringthego-around,a
climbatthebestangleofclimbspeed(81-83KIAS)with50%flapshastobeachieved.Afterclearing
anyobstacles,theprocedurestatestoretracttheflapsandacceleratetothenormalflaps-upclimb
speed.
Aircraftstallcharacteristicsareconventional.Power-offstallsmaybeaccompaniedbyaslightnose
bobbingiffullaftstickisheld.Power-onstallsaremarkedbyahighsinkrateatfullaftstick.Power-
offstallspeedsatmaximumweightforbothforwardandaftCGpositionsareasfollows:forFlapsUP
(0%)–69KIASwithwingslevel(0°bank),forFlaps50%-63-66KIASwithwingslevel(0°bank),for
FlapsFULL(100%)-59-61KIASwithwings level(0°bank).Thealtitudelossforawings levelstall is
definedas250ftormore.KIASvaluesmaynotbeaccurateatstall.
Whenpracticingstallsataltitude,itisnotedthatastheairspeedisslowlyreduced,aslightairframe
buffetwillbenoticed,thestallspeedwarninghornisactivatedbetween5and10ktsbeforethestall,
andtheCrewAlertingSystemdisplaysaSTALLwarningannunciation.Normally,thestallismarkedby
agentlenosedropwhilethewingscaneasilybeheldlevelorinthebankwiththecoordinateduseof
TUGrazIMasterthesis
EAppendix
E-3
theaileronsandrudder.Uponstallwarninginflight,recoveryhastobeaccomplishedbyimmediately
reducingbackpressuretomaintainsafeairspeed,addingpower ifnecessaryandrollingwings level
withthecoordinateduseofthecontrols.
Awarningreferstoextremecaretobetakentoavoiduncoordinated,acceleratedorabusedcontrol
inputswhenclosetothestall,especiallywhenclosetotheground(rf.(POH-SR20,2015,p.4-21,4-3,
4-22,4-23.5-12)).
POH,Section7–AirplaneandSystemsDescriptiondescribesthevariousaircraftsystems:
AvionicsSystem-ThePerspectiveIntegratedAvionicsSystemprovidesadvancedcockpitfunctionality
and improved situational awareness through the use of fully-integrated flight, engine,
communication,navigationandmonitoringequipment.ThePrimaryFlightDisplay,locateddirectlyin
front of the pilot, is intended to be the primary display of flight parameter information (attitude,
airspeed,heading,andaltitude)duringnormaloperations.
FlightControls-Theairplaneusesconventionalflightcontrolsforailerons,elevatorandrudder.The
controlsurfacesarepilotcontrolledthrougheitheroftwosingle-handedsidecontrolyokesmounted
beneaththeinstrumentpanel.Thelocationanddesignofthecontrolyokesalloweasy,naturaluseby
thepilot.Thecontrolsystemusesacombinationofpushrods,cablesandbellcranksforcontrolofthe
surfaces.
Pitch trim is provided by adjusting the neutral position of the compression spring cartridge in the
elevator control system bymeans of an electricmotor. It is possible to easily override full trim or
autopilotinputsbyusingnormalcontrolinputs.
Rolltrimisprovidedbyadjustingtheneutralpositionofacompressionspringcartridgeintheaileron
control systembymeansofanelectricmotor.Theelectric roll trim isalsousedby theautopilot to
position the ailerons. It is possible to easily override full trim or autopilot inputs by using normal
controlinputs.
Yaw trim is provided by spring cartridge attached to the rudder pedal torque tube and console
structure. The spring cartridge provides a centring force regardless of the direction of rudder
deflection.Theyawtrimisground-adjustableonly.
Engine - The airplane is powered by a Teledyne Continental IO-360-ES, six-cylinder, normally
aspirated,fuel-injectedenginede-ratedto200horsepowerat2700RPM.
The single-lever throttle control on the console adjusts the engine throttle setting in addition to
automaticallyadjustingpropellerspeed.Theleverismechanicallylinkedbycablestotheairthrottle
body/fuel-meteringvalveandtothepropellergovernor.MovingthelevertowardsMAXopenstheair
throttle butterfly and meters more fuel to the fuel manifold. A separate cable to the propeller
TUGrazIMasterthesis
EAppendix
E-4
governoradjusts thegovernoroilpressure to increasepropellerpitch tomaintainengineRPM.The
system is set tomaintainapproximately2500RPMthroughout the cruisepower settingsand2700
RPMatfullpower.
Percent power is shown in the upper left corner of the synoptic ENGINE page as both a simulated
gageandadigital value.Thedigitalpercentpowervalue isdisplayed inwhitenumeralsbelowthe
gage.Thedisplayunitscalculatethepercentageofmaximumenginepowerproducedbytheengine
based on an algorithm employingmanifold pressure, indicated air speed, outside air temperature,
pressurealtitude,enginespeed,andfuelflow.
WingFlaps-Theelectrically-controlled,single-slottedflapsprovidelow-speedliftenhancement.The
flaps are selectively set to three positions: 0%, 50% (16°) and 100% (32°) by operating the FLAP
control switch. The FLAP control switch positions the flaps through a motorized linear actuator
mechanicallyconnectedtobothflapsbyatorquetube.Proximityswitches intheactuator limitflap
traveltotheselectedpositionandprovidepositionindication.Anairfoil-shapedFLAPScontrolswitch
islocatedatthebottomoftheverticalsectionofthecenterconsole.Thecontrolswitchismarkedand
hasdetentsatthreepositions:UP(0%),50%and100%.TheappropriateVfespeedismarkedatthe
flap50%and100%switchpositions.Settingtheswitchtothedesiredpositionwillcausetheflapsto
extend or retract to the appropriate setting. An indicator light at each control switch position
illuminateswhenthe flaps reach theselectedposition.TheUP (0%) light isgreenand the50%and
100%lightsareyellow.
StallWarningSystem -Theairplane isequippedwithanelectro-pneumaticstallwarningsystemto
provideaudiblewarningofanapproachtoaerodynamicstall.Thesystemcomprisesan inlet in the
leadingedgeoftherightwing,apressureswitchandassociatedplumbing.
Astheairplaneapproachesastall,thelowpressureontheuppersurfaceofthewingsmovesforward
aroundtheleadingedgeofthewings.Asthelow-pressureareapassesoverthestallwarninginlet,a
slightnegativepressureissensedbythepressureswitch.Thepressureswitchthenprovidesasignal
to cause thewarning horn to sound, the red STALLwarning crew-alerting-system annunciation to
illuminate,and,ifengaged,theautopilotsystemtodisconnect.
Thewarning soundsatapproximately5 ktsabove stallwith full flapsandpoweroff inwings level
flightandatslightlygreatermarginsinturningandacceleratedflight.
Thesystemoperateson28voltsofdirect-currentsuppliedthoughthe2-ampSTALLWARNINGcircuit
breaker.Astallwarningsystempre-flightcheckisexplainedinthePOH(rf.(POH-SR20,2015,p.7-8,
7-10,7-12,7-35,7-39,7-25,7-76)).
TUGrazIMasterthesis
EAppendix
E-5
POH,Section10–SafetyInformationCAPSdescribesthatCAPSisdesignedtolowertheaircraftand
itspassengerstothegroundintheeventofalife-threateningemergency.CAPSdeploymentislikely
to result indamage to theairframeandpossible injury toaircraftoccupants. Itsuse shouldnotbe
taken lightly. Instead, possible CAPS activation scenarios should bewell thought out andmentally
practicedbyeveryCirruspilot.PilotswhoregularlyconductCAPStrainingandthinkaboutusingCAPS
willoftenhaveahigherprobabilityofdeployingCAPSwhennecessary.Cirrusalsorecommendsthat
pilotsdiscussCAPSdeploymentscenarioswithinstructorsaswellasfellowpilotsthroughforumssuch
as the Cirrus Owners and Pilots Association. In the event of a spin or loss of aircraft control,
immediate CAPS activation is required. In other situations, CAPS activation is at the informed
discretionofthepilotincommand.CAPShasbeenactivatedbypilotsatspeedsinexcessof180KIAS
onmultipleoccasionswithsuccessfuloutcomes.WhilethebestspeedtoactivateCAPSisbelow133
KIAS,atimelyactivationismostimportantforloss-of-controlsituations.
Loss of controlmay result frommany situations, such as a control system failure (disconnected or
jammedcontrols),severewaketurbulence,severeturbulencecausingupset,severeairframeicingor
pilotdisorientationcausedbyvertigoorpanic.Iflossofcontroloccurs,theCAPSshouldbeactivated
immediately. The POH further warns that in the event of a spin, immediate CAPS activation is
mandatoryand thatunderno circumstances should thepilotattempt to recover froma spinother
thanbyCAPSactivation.
Regardingpilotincapacitation,whichmaybetheresultofanythingfromapilot’smedicalcondition
to a bird strike that injures the pilot, if the passengers are not trained to land the aircraft, CAPS
activation by the passengers is highly recommended. This scenario should be discussed with
passengerspriortoflightandallappropriatepassengersshouldbebriefedonCAPSoperationsothey
couldeffectivelydeployCAPSifrequired.
GeneralDeploymentInformationstatesthatnominimumaltitudefordeploymenthasbeenset.This
is because the actual altitude loss during a particular deployment depends upon the airplane’s
airspeed,altitudeandattitudeatdeploymentaswellasotherenvironmentalfactors.However,inall
cases, the chances of a successful deployment increase with altitude. In the event of a spin,
immediate CAPS activation is mandatory regardless of altitude. In other situations, the pilot in
command may elect to troubleshoot a mechanical problem or attempt to descend out of icing
conditions if altitude and flight conditions permit. As a data point, altitude loss from level flight
deploymentshasbeendemonstratedat less than400 ft.Deploymentat sucha lowaltitude leaves
littleornotimefortheaircraft tostabilizeunderthecanopyor for thecabintobesecured.A low-
altitude deployment increases the risk of injury or death and should be avoided. If circumstances
permit, it isadvisable toactivate theCAPSatorabove2000 ftAGL.AfteraCAPSdeployment, the
TUGrazIMasterthesis
EAppendix
E-6
airplanewilldescendatlessthan1700fpmwithalateralspeedequaltothevelocityofthesurface
wind.TheCAPSlandingtouchdownisequivalenttogroundimpactfromaheightofapproximately10
ft.While theairframe,seats,and landinggeararedesignedtoaccommodatethestress,occupants
must be prepared for the landing. The overriding consideration in all CAPS deployed landings is to
preparetheoccupantsforthetouchdowntoprotectthemfrominjuryasmuchaspossible
(rf.(POH-SR20,2015,p.10-4,10-5,10-6,10-7)).
RelevantAspects-SR20FlightOperationsManual(FOM)
ReissueAwastheactualrevisionnumber(revisedFebruary2011)atthetimeoftheaccidentandit
wasstillunrevisedandvalidatthetimeofpublicationofthisthesis:
FOM,Section1-IntroductiondescribesthatproceduresintheFOMarederivedfromproceduresin
the FAA-approved Airplane FlightManual (AFM). Cirrus Aircraft has attempted to ensure that the
data contained agreeswith the data in the AFM. If there is any disagreement, the Airplane Flight
Manualisthefinalauthority(rf.(FOM-SR20,2011,p.1-1)).
FOM,Section2-GeneralOperatingProceduresdescribesintheCurrencyRequirementssectionthat
it is recommendedthatallpilotsoperate inaccordancewiththepoliciesandproceduresprescribed
within the FOM. In no casedoes it relieve the PIC from the responsibility ofmaking safe decisions
regarding the operation of the aircraft. Regarding initial training, Cirrus pilots should satisfactorily
complete the Cirrus Transition Training Course, Advanced Transition Training Course, Avionics
Differences,AirframeandPowerPlantDifferences,or theCirrusStandardized InstructorPilot (CSIP)
CoursepriortoactingaspilotincommandofaCirrusaircraft.
In respectof recurrent training,Cirruspilotsshouldcomplete recurrent trainingataCirrusTraining
Center(CTC)orwithaCSIPundertheguidancefoundintheCirrusSyllabusSuite.Recurrenttraining
emphasizes aeronautical decision-making, risk management, and airmanship, which leads to
increased proficiency. The recurrent training program provides an opportunity to meet the
requirementsofabiennialflightrevieworinstrumentproficiencycheck.
Cirrus pilots should maintain VFR currency by completing each of the following items in a Cirrus
aircraft:CirrusTransitionTrainingcourse,threetakeoffsandthreelandingstoafullstopwithinthe
previous60days,and10hoursasthePICwithintheprevious60days.Cirruspilotsshouldflywitha
Training Center Instructor (TCI) or with a CSIP tomeet the flight currency requirement if currency
lapses.
TUGrazIMasterthesis
EAppendix
E-7
Regarding personal minimums and risk assessment, all Cirrus pilots should regularly assess their
personal risk factorsanduse them todeveloppersonalminimums forwind, ceilingandvisibility.A
matrix in the FOM is available to establish the risk category (Author’s note: refer to L Appendix).
Pilotsshouldre-evaluatetheirriskcategoryonaquarterlybasisoranytimethatamajormilestone
occurs. This category should be applied to the recommended personal minimums found in the
Envelope of Safety. Note that the “Envelope of Safety” Table describes recommended personal
minimums forwind, ceiling, and visibility based on the pilot’s risk category, time of day, and pilot
rating.TheseminimumsarefollowedbycompanypilotsatCirrusAircraft(rf.(FOM-SR20,2011,p.2-
2,2-3,2-8,2-4,2-5)).Regardingtakeoffandlandingwindproficiency,theFOMdescribesthataCirrus
pilot shouldnotattempt to takeoffor landwhenthewindspeedandcrosswindcomponentexceed
the individual's capabilities.Adecision shouldbemade topostpone the flight if theweather isnot
acceptable(rf.(FOM-SR20,2011,p.2-5,2-11)).
A sterile cabin should be observed during departure, arrival andabnormal/ emergency operations,
andduringsterilecabinoperationsalldistractionssuchassatelliteradio,non-flightrelatedactivities
and unnecessary communicationwith passengers should beminimized (rf. (FOM-SR20, 2011, p. 2-
19)).
FOM, Section 3 - Standard Operating Procedures describes the recommended procedures when
operatingaCirrusaircraft.CirruspilotsareencouragedtofollowtheproceduresoutlinedintheFOM,
use their best judgment, and adapt the procedures when handling non-standard situations. The
majorityofCirrusaircraftoperationsareconductedonasingle-pilotbasis.Theworkloadassociated
withflyingtheaircraft,configuringandmonitoringavionics,communicatingwithairtrafficcontrol,
anddecision-makingrequirespilotstoefficientlymanagealltaskswhilemaintainingpositiveaircraft
control at all times. The following SRM procedures have been adapted from cockpit procedures
commontodualpilottransportcategoryaircraft.Inordertoensurethehighestlevelsofsafety,itis
strongly recommended that these single-pilot operating procedures are incorporated into the
operationoftheaircraft:
Priorityof Tasks - Thenumberonepriorityof thepilot is tomaintainaircraft control. Pilots should
maintain a high level of vigilance during periods of high and lowworkload to ensure that aircraft
control isalwaysmaintained. Onceaircraft control isassured,pilots should setandverify that the
avionics are correctly configured for navigation. This includes creating andmodifying flight plans,
selectingpropernavigationsourcesand/ortuningnavigationfrequencies.Useoftheautopilotmay
assistthepilotwithaccomplishingthesetasks.Communicationisanimportanttaskintheaircraftbut
TUGrazIMasterthesis
EAppendix
E-8
itfollowsaircraftcontrolandnavigationasapriority.Thistaskincludessettingassignedfrequencies,
controllingcommunicationvolumeandrespondingtoATCinstructions.
Theuseofstandardoperatingprocedureswillallowforsingle-pilotoperationswithhigher levelsof
safety and efficiency. Following standard procedures during flight operations will develop habit
patterns through repetition that allow pilots to be most efficient while completing tasks and
configuringtheaircraftforvariousphasesofflight.
The use of all available resources during flight in single-pilot operations will allow pilots to make
betterandmoretimelydecisions.Manyresourcesareavailabletopilots,suchasATC,FlightWatchor
FlightServiceStations,on-boardweatherdisplays,on-boardchartdisplays,andevenpassengers.
When used properly, checklists enhance the safety of flight by confirming that the aircraft is
appropriatelyconfiguredfortheflightcondition.Atthesametime,checklistsexpeditethecompletion
ofproceduresthatarenecessarytotransitiontosubsequentphasesofflight.
Regarding to passenger flight briefing, the pilot should provide a safety briefing, referencing the
passengerbriefingcard, toallpassengerspriortoeachflight.Asaminimum,passengersshouldbe
briefedonthefollowingitems:CAPS,smoking,seatbelts,doors,emergencyexits/egresshammerand
the use of oxygen. The pilot should also discuss sterile cabin procedures and other information as
necessary(rf.(FOM-SR20,2011,p.3-1,3-2,3-3,3-21)).
Ago-aroundshouldbeexecutedany time thatanapproachdoesnotmeet thestabilizedapproach
criteria.Ago-aroundshouldbecompletedfrommemorysinceitisatime-criticalmaneuver.Thefirst
priority of executing a go-around is to stop the aircraft’s descent. It is necessary to smoothly and
promptlyapplyfullpower(increasepowerlevertothefullforwardposition,ensurefullpowerisused
anddonotstopatanydetentsalongpowerlevertravel)whilesimultaneouslylevelingthewingsand
pitchingtheaircrafttostopthedescent.Theflapsshouldberetractedto50%,butnotfullyretracted
atthispointinthego-aroundbecauseitmayleadtoexcessivealtitudeloss.
Regardingnormallandings,theFOMsaysthattheyshouldbemadewith100%flaps.Finalapproach
speeds should beadjusted to account for gusts exceeding10kts by addinghalf of the gust factor.
Referringto“crosswindlandings”,theyshouldbemadewith100%flaps(rf.(FOM-SR20,2011,p.3-
77,3-81)).
FOM,Section4,AbnormalandEmergencyProcedures-CAPSDeploymentdescribesthatemergency
situationsinanaircraftarealwaysstressfulandpilotsmayoverlookallavailableoptionsforsurviving
theemergency.PilotswhoregularlyconductCAPStrainingandthinkaboutusingCAPSwilloftenhave
a higher probability of deploying CAPSwhennecessary. PerformingCAPS training in a Cirrus flight
trainingdeviceorsimulatorishighlyrecommended.Itisalsorecommendedthatfrequentflying
TUGrazIMasterthesis
EAppendix
E-9
passengers complete CAPS training in a Cirrus simulator to develop the ability to properly activate
CAPS.Regarding“unusualattitudes”itisadvisedthattheyaremostlikelytobeencounteredbypilots
wholackinstrumentskills,VFRpilotswhohaveinadvertentlyenteredIMC,orpilotsexperiencingan
abnormallyhighworkload.Pilotswhohaveenteredanunusualattitudehavetemporarilylostaircraft
controlorfailedtomaintainaircraftcontrol.Atthemomentofrecognition,thepilotmustmakean
immediate decision regarding whether the aircraft can be recovered using traditional recovery
techniques such as amanual recovery, engaging the autopilot (if within limitations), or activating
CAPS. Immediateactionby thepilot is requiredto recover theaircraft regardlessofwhichrecovery
methodischosen.Itisimportanttonotethatpilotswhohavelostaircraftcontrolmaybedisoriented
beyond the pointwhere traditional, hand flown recovery techniques are effective. CAPS activation
maybethebestrecoveryoptionavailable.Preventingunusualattitudesisthebestcourseofaction.
Pilotsareencouragedtousetheautopilotduringperiodsofhighworkload,butshouldnotbecome
overly-dependentontheautopilotforaircraftcontrol(rf.(FOM-SR20,2011,p.4-2,4-40)).
TUGrazIMasterthesis
FAppendix
F-1
APPENDIXF
ResultsRaisedbytheNTSBFinalReport
This appendix describes the probable causes from the official Aviation Accident Final Report
publishedonDecember12,2017tobecomparedwiththefinalresultsofthisthesis:
• Thepilot’simpropergo-aroundprocedurethatdidnotensurethattheairplanewasatasafe
airspeed before raising the flaps, which resulted in an exceedance of the critical angle of
attackandanacceleratedaerodynamicstallandspinintoterrain.
• The initial local controller'sdecision to keep thepilot in the trafficpattern, and the second
local controller's issuance of an unnecessarily complex clearance during a critical phase of
flightcontributedtotheaccident.
• Thepilot’slackofassertivenesswasalsoacontributingfactor
(rf.(NTSB,AviationAccidentFinalReport,2017,p.2)).
In addition to the final report, fifteen documents36 related to the N4252G accident have been
publishedviatheDocketManagementSystem(DMS)ontheNTSBpublicwebsite37forunrestricted
download. For the purpose ofmodeling the prevailing accident with STAMP (Leveson, 2011), the
authorhasretrievedthesedocumentsandfurtheranalysedtheminmoredetail.
36AirTrafficControlFactualReport,HOUTowerAccidentPackage,OUNTowerAccidentPackage,HOUTowerOperatingProcedures,N4252GRadarTargetFile-HOUASRGoogleEarthKMLTargetFile,HoustonApproachControlRadarFile (Shelf Item),CockpitDisplays -Specialist’sFactualReport,Attachment1 -CockpitDisplaysFactualReport,PilotToxicology,StatementofPartyRepresentativestoNTSBInvestigation,WeatherSummary,WreckageDiagram(CourtesyofHoustonPD),CFIStatements,Photos,StallSpeeds37https://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=60618&CFID=2395938&CFTOKEN=81732fd00bba5423-5AB1BC7B-CB39-E91F-3732EB517FD2FBDB
TUGrazIMasterthesis
GAppendix
G-1
APPENDIXG
ChainofEvents
TheNTSB,AirTrafficControl,GroupChairman'sFactualReport(2016)desribesthechainofeventsas
follows:
N4252Gdeparted fromUniversityofOklahomaWestheimerairportat10:09CDTen route toHOU.
The pilot contacted Houston Approach at 12:27:48, reporting that she had received automated
terminalinformationservice(ATIS)informationHotelforHOU38.Thecontrollerinstructedthepilotto
descend to 5000 ft andmaintainVFR39. The flight received routineVFRhandlingand subsequently
descendedto1800ft.
At12:38:40, thecontroller toldthepilot toexpecta leftbasetothetrafficpatternforrunway4at
HOU.Vectoringandtrafficadvisoriescontinued,andat12:51:38,thecontrolleradvisedthepilot,“...
you’refollowingaBoeing737about1:00o’clockand5miles-onafourmilefinalat2000,cautionfor
waketurbulence”.Thepilotreportedtheotheraircraftinsight.
At12:52:20,thecontrollerinstructedthepilottoflyheading095tofollowthetraffic,issuedanother
waketurbulenceadvisory,andtransferredcommunicationstoHOUtower.Thepilotacknowledged.
ThepilotcontactedtheHOUtowerLCpositionat12:52:47andreportedat1600ft.Thepositionwas
beingworkedbyatrainee(LCT)andaninstructor(LCI).Thetraineemissedthesourceofthecalland
thought itwasaSouthwestAirlines(SWA)flight.Herespondedas if theSWApilothadcalled,then
realizedthatithadactuallybeenthepilotofN4252G.Afterresolvingtheconfusion,theLCTcontroller
transmitted,“Cirrus4252GHobbytower,you’renumber2followinga737ona3milefinal,caution
wake turbulence, runway 4 cleared to land”. The pilot read back the instructions correctly. The
controllerthenaskedwheretheaircraftwouldbeparking,andthepilotresponded,“We’llbeparking
atMillionAir,4252G”.
At12:53:51,theLCIcontrollertransmitted,“Cirrus4252Gproceeddirecttothenumbers,you’regoing
tobeinsidea737interceptinga10milefinal”.Thepilotasked,“OK,you’dlikemetoproceeddirect
tothenumbers,4252G?”TheLCIcontrollerresponded,“November52G,whatdidapproachtellyou
38InformationHotelwasbroadcastedafter11:53CDT,andreportedHOUweatherconditionsaswindwith100degreesat8kts,visibilityof10miles,scatteredcloudsat3,500feet,andabrokenceilingat18000feet(TheauthorofthisthesisrecalculatedthewindcomponentsconsideringFigure6-4Windcomponentdiagramasfollows:100°/8ktsequals2ktstailwindand8ktscrosswindforrunway35(356°runwaytrack)versus4ktsheadwindand7ktscrosswindforrunway4(041°runwaytrack)).39“MaintainVFR” isan instruction issued topilots to remain in flight conditions suitable for visual flight rules(VFR).
TUGrazIMasterthesis
GAppendix
G-2
before?” The pilot answered, “Um, to left base runway 4 and follow the Boeing, 4252G”. The LCI
controlleragaininstructedthepilotto,“...proceeddirectthenumbersforrunway4,directtoHobby”.
At 12:54:24, the Hobby Final controller called the LC controllers to ask that they have the Cirrus
proceeddirecttothenumbers,andtheLCIcontrollerrespondedthatthepilothadbeendirectedtodo
so.
At 12:54:39, the LCT controller asked the pilot tomaintainmaximum forward speed and proceed
directtothenumbers,advisingherthattherewasa737on9milefinalfollowingtheCirrusthatwas
overtakingitby80kts.Thepilotrespondedthatshewouldproceeddirecttothenumbersandkeep
herspeedup.
At12:55:49,theLCTcontrollerbroadcaststoallaircraftthatHOUATISinformationIndiawascurrent,
altimeter29.94.ThepilotwasnotrequiredtoacknowledgetheupdatedATISannouncementanddid
notdoso.
At12:55:59,SWA235contactedHOU,reportingthattheywereon5milefinalforrunway4.TheLCT
controllerrespondedthattheywerenumber2followingaCirruson2milefinal,clearedthepilotto
land,andinstructedhimtoslowtofinalapproachspeed.
At12:56:19,theLCTcontrollerbroadcastsawindcheck,080degreesat13ktsgustingto18kt.
At 12:56:58, the LCI controller called N4252G, and the pilot responded. The LCI controller then
continued, “Yeah, I’ve got traffic behind you, just go-around and fly runway heading for now,
maintainVFR,andI’mgoingtoputyoubackonthedownwindforrunway35.Thewindsare090at
13gusts18[kt].Canyouacceptrunway35?”Thepilotresponded,“We’retoandlineupforrunway
35downwind”. The LCI controller then told thepilot to fly runwayheading for runway4 “for right
now”.Thepilotresponded,“We’ll flyrunwayheadingfor4,4252G”.TheLCIcontrollerthencleared
SWA235toland.
At12:57:34,theLCIcontrollertransmitted,“N52Gwhenablegoaheadandmakearightdownwind
nowforrunway35andthenwe’lljustgoaheadandkeepthatrightturn,runway35clearedtoland”.
The pilot read back, “OK, make a right downwind for runway 35?” The LCI controller continued,
“N52Gyesandjustkeeptherightturnallthewayaround,you’rejustgoingtorollrightintothebase
forrunway35,clearedtoland.I’vegotanother737on5milefinaltorunway4andyou’regoingto
beinfrontofhim”.Thepilotacknowledgedwith,“...turningaroundforrunway35”
At 12:58:10, the LCI controller said, “... just enter the downwind for runway 35,” and the pilot
acknowledged.
At12:58:16,theLCIcontrollertoldthepilotthathewouldcalltherightbaseturn.
At12:58:48,theLCTcontrollerprovidedatrafficadvisorytothepilotofN4252Gaboutanother737
inboundtorunway4,andthepilotreportedthe737insight.TheLCTcontrollerinstructedthepilotto
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makearightbasetofollow[passbehind]the737,andagainclearedthepilottolandonrunway35.
Thepilotreadback,“we’regoingtomakearightbasefollowingthem...forrunway35,N4252G”.
At12:59:20,theLCTcontrollertoldthepilotto“turnleftheading30degrees”.Thiswastoresolvea
perceivedconflictbetweenN52GandSWA235.Thepilotreadback,“turnleftheading30degrees”.
At12:59:30,theLCIcontrolleraskedthepilotifshe,“...wantedtofollowthe737torunway4?”The
pilotresponded,“Yes,thatwouldbegreat”.Thecontrollerthentoldhertofollowthe737torunway4
and cleared her to land. The pilot then asked, “Am I turning a right base now, 4252G?” The LCI
controller continued, “N52G roger, justmaneuver back for the straight-in, I don’t knowwhichway
you’regoingnow,so just turnbackaroundtorunway35”.Thepilot replied,“Turningto35, I’mso
sorryfortheconfusion,4252G”.TheLCIcontrollerresponded,“That’sOK,we’llgetit”.
At 13:00:13, the LCI controller asked the pilot which direction she was turning. She responded, “I
thought Iwasturningarightbasefor35,4252G”.TheLCIcontrollercontinued,“... that’sfine52G,
uh,justmakeituh,yousayyou’reinarightturn,keepittight,Ineedyoutomakeittight”.Thepilot
answered,“Keepingturntight,4252G”.
At13:00:31,thecontrollerprovidedatrafficalertto“0GA”abouttraffic1mileawayat900ft,which
wasN4252G. That pilot reported that hewas “looking,” and the LCI controller continued, “N52G I
needyoutouhthereyougo,straightintorunway35,clearedtoland”.Thepilotreadback,“Straight
in to runway 35 and I don’t believe I’m lined up for that”. The LCI controller acknowledged and
instructed the pilot to, “... turn to the right and climb and maintain 1600, right turn”. The pilot
acknowledged,and the LCI controller continued, “Yes,ma’am,headingabout040,”which thepilot
readbackcorrectly.
At13:01:16,theLCIcontrollertransmitted,“OK52G,let’sdothis.Canyoudoarightturnbacktojoin
the straight-in to 35? Could you do it like that?” The pilot replied, “Yes, right turn back to 35,
N4252G”.TheLCIcontrollerinstructedthepilottomakearightturn,“allthewayaroundtorunway
35,”andagainclearedthepilottoland.Thepilotacknowledged.
At thesametime, theHobbyFinalcontrollerwascalling the tower toofferaspace toputN4252G
behindanotheraircraft,N4JJ, inboundon the runway4 final. The LCI controllerdidnot respond to
thatcall.
At13:01:44,N4JJcontactedthetoweronavisualapproachtorunway4.TheLCIcontrollertoldthe
pilottoreducetominimumspeed,andadvisedthathewouldbenumber2fortheairportfollowinga
Cirruson1milefinalforrunway35.ThepilotofN4JJacknowledgedtheinformation.
At13:02:02,theLCIcontrollertransmitted,“Cirrus52G,OK,you’relookinggoodjustcontinuearight
turnforrunway35.Doyouseerunway35still?”Thepilotresponded,“Yes,35,4252Ghaveitinsight,
continuingmyrollaround”.TheLCIcontrollercontinued,“Yes,ma’am,yeahyou’regoodsoyoucan
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startyourdescenttorunway35there,anduhclearedto landon35”.Thepilotreplied,“Clearedto
landon35,52G, thankyouverymuch”.Thecontroller thenprovidedawindcheck,“...winds40are
100at15guststo20”.Thepilotresponded,“OK,thankyou,tryingto losealtitude4252G”.TheLCI
controllercontinued,“Noproblem,littlebitofwindofftheright”.
At13:03:01, theLCIcontrollertransmitted,“N52Gifyoudon’twantto land– ifthat’stoohigh,we
canputyoubackaroundthedownwind,don’t force it ifyoucan’t”.Thepilotanswered,“OK-we’ll
see, thank you,4252G”.At1303:25, the LCI controller toldher, “OK, I think you’re toohigh,Cirrus
52G, you might be too high”. The pilot replied, “OK - we’ll go-around then, N4252G”. The LCI
controllertoldthepilottomakerighttrafficforrunway35.Thepilotreplied,“Soundsperfect,right
trafficrunway35,4252G”.
At13:04:38,theLCIcontrollerclearedN4252Gtoland,stating,“...makerightdownwindtorunway
35,andyouareclearedtoland-therewillbenoothertrafficforrunway4sothisonewillbeeasy”.
The pilot read back, “Making right traffic for downwind for runway 35, 4252G”. The controller
continued, “N52Gaffirmative, and cleared to landon runway35 via the rightdownwindand right
base”.Thepilotthenreadback,“Thankyou–rightdownwind,rightbase,4252G”.
At13:06:00, theLCIcontroller issuedatrafficadvisorytothepilotofN4252G,stating,“... there’sa
737onshortfinalrunway4touchingdownrightinfrontofyousojustcautionwaketurbulenceright
thereatthatintersection”.Thepilotresponded,“OK,I’vegotthatinsight,N4252G”.
At 13:07:03, the LCI controller asked if the pilot of N4252G had runway 35 in sight. The pilot
answered that shedid, and the controller providedawind check41, “090at 13gust 18, runway35
again, cleared to land”. The pilot replied, “35 cleared to land trying to get [laugh] down again,
4252G”.
At13:07:49,apositionreliefbriefingoccurredontheLCpositionandanewcontrollertookover.
At13:08:21, the pilot reported, “... going around, third timewill be a charm”. The new controller
responded, “OK, Cirrus 52G, just go ahead and make the left turn now to enter the downwind,
midfielddownwindforrunway4,ifyoucanjustkeepitinanicetightlowpattern,I’mgoingtohave
traffic 4 miles behind you so I need you to just kind of keep it in tight if you could”. The pilot
responded, “OK, this time will be runway 4, turning left, 4252G”. The controller continued, “And
actuallyImightendupsequencingyoubehindthattraffic,he’son4milesaminute,umitisgonnabe
40TheauthorofthisthesisrecalculatedthewindcomponentsconsideringFigure6-4Windcomponentdiagramasfollows:100°/15ktssteady(gustsupto20kts)equals4kts(gustsupto5kts)tailwindand14kts(gustsupto19kts)crosswindforrunway35(356°runwaytrack).41TheauthorofthisthesisrecalculatedthewindcomponentsconsideringFigure6-4Windcomponentdiagramasfollows:090°/13ktssteady(gustsupto18kts)equals1kt(nogusts)tailwindand13kts(gustsupto18kts)crosswindforrunway35(356°runwaytrack).
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abittightwiththeonebehinditsowhenyougetonthedownwind,stayonthedownwindandadvise
mewhenyouhave that737 in sight.We’ll eitherdo4orwemight swingyouaround to35uhuh
ma’am,ma’amuhstraightenupstraightenup!”
There were no further contacts with the pilot. N4252G crashed northwest of the airport in a
commercial parking lot, and the tower supervisor reported the accident to emergency services (rf.
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.4,5,6,7)).
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APPENDIXH
InterviewswithATCControllersheldbyNTSB
ThisappendixsummarizesrelevantfactsofpersonalinterviewsheldbytheNTSBwithinvolvedATC
controllersasdescribedintheNTSB,AirTrafficControl,GroupChairman'sFactualReport(2016).For
thisthesis,nameshavebeenerasedandreplacedbytheshortformoftheirpositionsbytheauthor.
HOULCI(OJTI)-Controller
TheATCgroupinterviewedtheLCIonJune15,2016.
HebeganworkingfortheFAAinDecember2002atLongviewATCT(GGG).InFebruary2012,theLCI
transferredtoHOU.HewascertifiedonallpositionsatHOUbyDecember2012,andheldacurrent
FAAmedicalcertificate.
On the day of the accident, the LCIwasworking his regular assigned shift of 05:30 to 13:30 CDT,
assignedtoprovideon-the-jobtraining(OJT)toatrainee(LCT)ontheLCposition.Onascaleof1to5,
the LCI described the traffic during period before the accident as “around a 3”. There were no
personaloroperationalissuesaffectinghisperformance,andhedidnotfeelfatiguedduringtheshift.
Duringtheprecedingmonth,hehadworked“acouple”ofovertimeshifts,andtypicallyworkedone
midnightshifteveryweek.
TheLCIdidnotfeelthatheneededtointervenemuchduringthetrainingsessionuntilN4252Gwas
inbound.Hesaidthatnormallyaircraftaresequencedbyapproachcontrolandthetowerjustclears
them to land. If the spacingwere to diminish unacceptably, then hewould either send one of the
aircraftaroundorsendthembacktoapproachtobere-sequenced.Hestatedthatapproachnormally
givesa“goodfeed”totheairportanditisnotcommonforthetowertohavetopullsomeoneoffthe
approachorswitchthemtoadifferentrunway.Hedescribedtherelationshipbetweenthetowerand
approachcontrolasgood.
TheLCIrecalledfirstseeingN4252Ginboundfromthewestonamodifiedbasetorunway4.When
thepilotcheckedin,histraineethoughtthecallwasfromaSouthwestB737onfinal.Theycorrected
the confusion and cleared the pilot of N4252G to land on runway 4. The LCI asked the pilot if
approachhadissuedanyrestrictionsandthentoldhertoproceeddirecttotherunwaynumbers.He
sawN4252Gjointhefinalandthenslowdown.
HenoticedthespacingdecreasingbetweenN4252Gandthefollowing737,sohetoldN4252Gtogo-
around.Hemadethatdecisionduetothe“flow”inuseattheairportandtheknowledgethatrunway
35wasalsoavailableforlanding.Thiswasacommon“out”thathehadusedmanytimestoresolvea
spacingissueratherthansendingtheaircraftbacktoapproachforresequencing.Hestatedthatifthe
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approachcontrollercalledtotakeanaircraftbackforsequencing,hewouldnotquestionitandwould
sendtheaircraftbacktoapproach.
TheLCItoldthepilottoenterrightdownwindforrunway35.N4252Govershotthefinalandwasnot
properlylinedupforrunway35.Theovershootstartedtolooklikeaproblemwiththeaircraftonthe
runway4 final, so theLCT issueda30-degree left turn for traffic.Thepilotseemedconfusedabout
whattodo,sotheLCItookoverthefrequencyandbeganworkingLConhisown.AfterN4252Gwas
linedupforrunway35,theaircraftlookedhigh(“acouplehundredftabovetherunwayatmidfield”),
soheagaininstructedthepilottogo-aroundandentertherightdownwind.Headdedthattherewas
no further traffic on the runway4 final, so thenext try “shouldbe easy”.He subsequently cleared
N4252G to landon runway35. Theaircraft endedup toohighagain, and thepilot reportedgoing
around.
TheFLMhadbeenmonitoringthelocalfrequenciesandcoordinatingonthelandlines.
TheLCIdidnotrecallhearinganyspecificlandlinecoordinationbetweentheFLMandapproach,but
generallywhen LC became busy the FLMhandled the coordinationwith approach control. The LCI
knewthat theFLMwasawareofN4252G’smultiplego-arounds.TheFLMdidnot interveneatany
timeduringtheincidentanddidnotaskquestionsabouttheeventafterwards.
TheLCI’s shiftwasalmostover, soanother LCcontroller (LCC)hadcome toLC to completea relief
briefingandtakeovertheposition.TheLCCmovedtothemonitorpositionfortherequired2-minute
positionoverlapperiod.HesawN4252Gturnleftcrosswindoffrunway35andthen“nosetheaircraft
straight down”. Based on radar and visual observation, the LCI estimated that N4252G was
approximately500ftabovegroundjustbeforetheaccident.HesawtheFLMpickupthecrashphone,
butwasnotawarewhichemergencyservicesrespondedtothescene.TheLCCcontinuedworkingthe
LCposition,butdeparturesatHOUwerestoppedduetotheaccident.
While he was dealing with the spacing issue between N4252G and the trailing SWA flight, the
approachcontrollercalledandtheLCIrepliedthathewouldtakecareof[thespacing].Hestatedthat
spacingissuesrequiringago-aroundorarunwaychangeonlyoccurredaboutonceaweek.
Afacilitybriefingitemprovidedtothegroupstatedthatitwasa“bestpractice”tohandlego-arounds
by transferring them back to the approach control for resequencing, while the I90/ HOU letter of
agreement stated that go-arounds should be handled as a satellite airport departure42 that is
transferredbacktoI90.Askedaboutthedisagreement,theLCIsaidthatkeepinggo-aroundaircraftin
the pattern was frequently coordinated with I90 and was a very standard alternate plan. It was
42Title 14 CFR part 91.129(c)(2)(ii) states that departing flight from a satelliteairportwithout an operatingcontrol tower must establish and maintain two-way radio communications with theATCfacility havingjurisdictionovertheClassDairspaceareaassoonaspracticableafterdeparting.
TUGrazIMasterthesis
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common for FLMs to coordinatewith I90onbehalf of LC,but thatwouldnotnecessarily lead toa
conversationbetweenLCandtheFLMaboutwhathadbeendiscussed.
IntheLCI’sexperience,havinganaircraftmisstherunwaytwicewasunusual,andthiswasthefirst
timethathehadseensuchanoccurrence.AstheaircraftwasVFR,keepingitinthepatternwasthe
“normal”response.
TherewereaboutfivedevelopmentalsatHOU,andtheyweregenerallywellpreparedforOJTafter
completingtheirclassroomtraining.TheLCIsaidthathewouldnothavedoneanythingdifferentlyin
thissituation,andthatifalocalassistpositionhadbeenopenitwouldnothavechangedanything.
Overall,theLCIfeltthatHOUdoesaverygoodjobandusesgoodprocedures,butnotedthatthere
wasalwaysroomforimprovement.
TheLCIhadbeenonadministrativeleaveuntilWednesday,June15,2016,andhadnotparticipatedin
any discussionswith facilitymanagement about the accident. He has not participated in any crew
briefingssincehecametoHOU,andsaidtherewasnopracticeofdiscussingincidentsandaccidents
aslearningexperiences.Hewasnotawareofthespecificmembershipofthefacilitysafetycouncil(rf.
(NTSB,AirTrafficControl,GroupChairman'sFactualReport,CEN16FA211,2016,p.20,21,22)).
HOUFLM-Controller
TheATCgroupinterviewedtheFLMonJune15,2016.
He began working for the FAA in February 1991 at the FAA Academy, and was first assigned to
Burbank ATCT. He later transferred to Chicago Center, Rockford ATCT, ChicagoMidway ATCT, Las
VegasATCT,DaytonATCT, andDallas FortWorth InternationalATCTbefore coming toHOUas an
FLMinJune2015.HewascertifiedonallpositionsatHOUandheldacurrentmedicalcertificate.He
typicallyworked12to16hoursamonthontheLCandgroundcontrol(GC)positions,andotherwise
spentalmost40hoursaweekinthecabsupervisingtheoperation.
Onthedateoftheaccident,theFLMwasworkinghisregularassignedshiftof06:30to14:30CDTand
performinghisregularFLMduties.Thedaystartedwithsevencontrollers,includingonetrainee,but
around noon hewas notified that one of the controllers assigned to the shift had beenmedically
disqualified.Anothercontrollerhadalreadybeenapprovedforannual leave,soonlyfivecontrollers
wereavailable.Therewerenounusualequipment issuesaffectingtheoperation.Thewindsstarted
outvariablefrom050to110degrees,andincreasedinstrengthasthedaywenton.Therewereno
reports of wind shear or other wind issues during the shift. The FLMwas unsure where the wind
sensorwaslocatedontheairport,butnotedthattherewassoontobeachangeinthesystem.
Intheperiodleadinguptotheaccident,HOUwaslandingrunways4/35,anddepartingrunways4,
12L/R,and35.Mostofthetrafficwaslandingonrunway4anddepartingfromrunway12R.There
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wastraininginprogressontheLCposition,whichhewasmonitoringtothemaximumextentpossible
alongwithhisotherdutiesatthesupervisorypositioninthebackofthecab.
TheFLMfirstbecameawareofN4252Gwhenhesawtheaircraftonradaronaleftbaseforrunway
4,withotherjettrafficinboundonfinal.ThetrainingteamonLCdecidedtoturnN4252Gdirecttothe
runway.At thesametime,heheardapproachcallandask the tower to turnN4252Gdirect to the
runway.When the LCT controller issued the instruction,N4252Gmade a slow turn and proceeded
directlytotheendofrunway4.
TheFLMnoticedthattheB737trafficbehindN4252Gwasslowingbutstillovertakingtheaircraft.LC
toldthepilotofN4252Gtogo-aroundandflyrunwayheading.N4252Goverflewabout3⁄4ofrunway
4 before LC instructed the pilot to enter right downwind for runway 35. After N4252G turned
downwind,itstarteddriftingtowardstheothertrafficonfinalforrunway4.TheFLMheardtheLCT
controllertellN4252Gtoturnleft20degrees43,andthentheLCIcontrollertookovertheposition.
TheLCItoldthepilotofN4252Gtomakeagradual270degreeturnaroundtorunway35.Theplan
wastoputtheCirrusonrunway35throughagapbetweentherunway4arrivals.TheCirruswasnot
descendingverymuch.TheLCIthentoldthepilotthattheaircraftlookedtoohighandtogo-around.
TheLCIthensequencedN4252Gontoanotherdownwindforrunway35andclearedthepilottoland.
WhileN4252Gwas on downwind to runway35 for the second time, the FLM called approachand
askedthemtoslowtheirnextarrivaldowntobuildinalittlemorespacefortheCirrus.Theapproach
controllertoldtheFLMthathewouldtakeN4252Gback,buttheFLMsawthatN4252Gwasalready
turning base, so he told approach that the tower would just work the aircraft. The FLM did not
coordinate with LC about the call. Although the spacing between the runway 4 arrivals looked
adequate,theFLMsawN4252Gcominginhighonfinalagain(aroundtheheightofthetower),and
thepilotreportedthattheyweregoingaround.
TheLCI’sshiftwasending,sotheFLMhadtheLCTmovetoGCandsendacontroller(LCC)fromGCto
LCtorelievetheLCI.Afterthereliefbriefingwascompleted,theFLMheardtheLCCcalmlytalkingto
thepilot,whobythenwasontheupwindfollowingthego-around.TheFLMwasonthephone,sohe
didnothearexactlywhatwas said,althoughboth the controllerandpilot soundedcalm.TheFLM
then heard LCC saying “straighten it out, straighten it out!” and realized that there had been an
accident.Heputtheregularphonedownandactivatedthecrashphone,reportingthatthecrashwas
abouthalfamileupAirfieldRoad.Emergencyvehiclesresponded.
43Author’snote:TheofficialNTSBreportandATCtranscriptdescribes30degrees,thereforeitisconsideredtobeanambiguityerror.
TUGrazIMasterthesis
HAppendix
H-5
TheFLMalso told the flightdata/ clearancedelivery controller to call theother controllerup from
lunchimmediately.Theairtrafficmanagercameuptothecabtoassistwithemergencynotifications.
TheFLMgottheLCCofftheLCpositionaboutfiveminutesaftertheaccident.Hewasunabletoget
theothercontrollersoffposition forabout15minutesdue tostaffing.TheFLMspent thenext two
hoursupinthetowercab.
Hedidnotdiscusstheeventsoftheaccidentwiththecontrollersinvolved.Hewasmostlyconcerned
for the controller’s well-being and did not want to talk to about the accident with them. The
controllersweregivensomeadministrativeleaveinadditiontotheirregulardaysofftodecompress
andparticipateinstresscounseling.TheFLMcontactedthemovertheweekendtoensurethatthey
werecopingaftertheaccident.
WhenaskedabouttheLCC’sinstructiontoN4252Gto“keepturnintight”,theFLMsaidthatitwas
notstandardphraseology.
TheFLMsaid that the speedsof theaircraft coming inon finalarea “hit ormiss”. Sometimes the
aircraft come in fast and other times slower. HOU does not normally put restrictions on the final
unlessunusualconditionsat theairportareaffectingrunwayoccupancytimesorotheroperational
issues.Onoccasions,HOUhastobreakanaircraftoutonfinal,butitwasnotasystemicissue.Ifan
aircraftgoesaround,therearetwochoices:toeithergobacktoapproachorcomeintorunway35.
About90percentofthetimeifasmallVFRaircrafthadtobere-sequencedoffrunway4,thetower
wouldkeep theaircraftandnothand itoff toapproach.Thiswasnormalhandling followingago-
around.TheFLMsaidthathedidnotgiveanyinstructionstoLCbecausetheyhadthesituationunder
control. As far as the FLM could tell, both approaches to runway 35 were good and should have
worked:theaircraftsimplydidnotdescend.Thefirstapproachtorunway4wouldnothaveworked
andsendingN4252Garoundwasthebestoption.IftheyhadnotpulledN4252Gout,theywouldhave
potentiallyhadtosendtwootheraircraftaround.
TheFLMhastriedtogetcrewbriefingstogethersincehegottoHOU,butstaffinghasbeenshortand
briefingshavebeendifficult toaccommodate.He tries tomeetwithhiscrewwhenhecan,but the
priorityistheoperationovercrewbriefs.TheFLMorganisedtwoall-handsbriefingsscheduledforthe
following week. The supervisors and training specialist were to cover the operation so all the
controllerscouldmeetwiththeATMandthefacilityNATCArepresentative.
TheFLMhadnotcompletedmanyPerformanceRecordsofConference(PRCs)todocumentcontroller
performance,andadmitted that itwasanerroronhispart.With the recentevents that theyhave
had, PRCs have become more common. The FLM stated that he has undertaken performance
management fromdayonebuthis documentationwaspoor. The FLM said that thenewATMhas
addressed performance management with the FLMs and has stressed documentation within the
TUGrazIMasterthesis
HAppendix
H-6
allowabletimeconstraints.Hesaidthatitwasdifficultdocumentingthisduetohisworkloadwiththe
schedule. He attended FLM training at the end of 2015, which helped him to better understand
performancemanagement.HehadnotcompletedanyPRCsrelatedtothisaccidentasofthedateof
thisinterview.HewillbediscussingtheaccidentandATCcommunicationswiththeATMtoseehow
he wants to handle it. The FLM reported receiving no specific personal training on performance
managementorquality control in thepastmonth,althoughhe received some trainingon resource
management.
TheFLMcouldnotexplainwhyHOUhadtheirrecentissues,buthasfoundthatsomepeoplewerenot
engaged like they should have been. Some controllers have never seen certain situations and that
openedupopportunitiestocoachthem.Ifhehadtograde44thefacilitymanagementeffortstobrief
employeesabout issuesandevents,hewouldgivethema“CtoCminus”.Hefelt that thevalueof
theseexperiencesarenottaughtsufficientlywell.Hehasnotbeen involved intheAirTrafficSafety
ActionProgram (ATSAP45) event reviewand skill enhancement trainingprocess yetasa supervisor,
andhedidnotfileanATSAPreportforthisaccident.Hewasunsurewhetheranyofthecontrollersdid
so.The local safety councilhadnotbeenveryactiveprior toa recentvisit from thecentral service
area Quality Control Group.While their activity level had recently increased, he had still not seen
muchinformationcomingoutofthegroup.
If the FLM had the opportunity to do anything at HOU, he would improve the communication
throughouttheentirefacility.Controllersmaybebriefedaboutanoccurrence,butthereistoolittle
timeavailabletoensurethatunderstandingandlearningoccurs.Whenhetalkstohiscrew,ifthereis
aspecifictopictoaddress,allsevenofhiscontrollersreceivethesamebriefing.Ifitisaweekduring
whichamoregenericdiscussionispossible,hehassessionsthataremoreofacoachingnature.
Management staffing at HOU was one ATM, three supervisors, and one training specialist. The
activitylevelplacedthefacilityrightinthemiddleoftheATC8levels.
Thetowerwasnotprimarilyusingrunway12forarrivalsbecausethewindhadnotpickedupuntil
theafternoonarrivalpushwasinprogress,anditwasnotagoodtimetochangerunways.Landing
onthe12swhilealsolandingonrunway4wasdifficultduetotheairportlayout.
Theapproachcontrolwasusuallycooperativeaboutrestrictionsrequestedbythetower.
44Author’snote:commongradesinUSschoolsarescalingfromA(excellent)viaB(good),C(average),D(belowaverage)toE(insufficient).45Author’snote:FAAmodeledATSAPasavoluntarysafetyreportingprogramthathelpstoresolvesafetyissuesthatotherwisemightnothavebeenidentifiedorresolved.Nopunitiveordisciplinaryactionswillbetakenasaresult, provided those errors are not the result of gross negligence or illegal activity (rf. (retrieved fromhttps://www.natca.org/index.php/insider-articles/2183-atsap-what-you-need-to-know)).
TUGrazIMasterthesis
HAppendix
H-7
When asked if he had ever participated in a System Service Review process, the FLM said he had
temporarilyfilledaslotonthelocalsafetycouncil foranevent involvingarunwaycrossingwithout
usingvisualaids.Thewholeprocesstook60to90minutes.Healsoparticipatedinthelasthalfofthe
“servicesrenderedteleconference”forthisevent.
WhenaskedaboutthedecisiontoputtheCirrusonrunway35withtheexistingcrosswind,FLMsaid
thatthetowerhadbeenusingrunway35alldayforavarietyofaircraftwithnoissues.Hethought
that the controllers were making good decisions and the sequencing with the runway 4 arrivals
lookedgoodbothtimes.Heneverfeltaneedtointervene.Theproblemseemedtobethatthepilot
never descended sufficiently to reach the runway (rf. (NTSB, Air Traffic Control, Group Chairman's
FactualReport,CEN16FA211,2016,p.22,23,24,25)).
HOULC-Controller
TheATCgroupinterviewedtheLCcontroller(hereincalledLCC)onJune16,2016.
TheLCCbeganworking for theFAA inNovember1988at theFAAAcademy.Heworkedat various
facilitiesincludingSantaMariaATCT,SanJoseATCT,andHOUsincethen,arrivingatHOUin1998.He
alsoworkedseventemporarydetailsatOshkoshATCTduringtheannualEAAevent.Hewascertified
onallpositionsatHOU.HeheldacurrentATCmedicalcertificate.
Onthedateoftheaccident,theLCCwasworkinghisregularly-assignedshiftof05:30to15:30CDT.
Therewerenounusualpersonalorequipmentissuesaffectinghisperformance.
TheLCCwasworkingGCwhenhebecameawareofN4252GinboundtoHOU.Herecalledseeingthe
aircraft on radar about five miles out and again on short final to runway 4. He did not observe
anythingunusualuptothatpoint.HeheardoneoftheLCcontrollerssendN4252Garound,butwas
unsurewhether itwas thedevelopmental (LCT)or the trainer (LCI)who issued the instructions.He
thenheardthelocalcontrolcontrollersequenceN4252Gtorunway35.Hewasgenerallyawarethat
theCirruswasinthepattern,butwasmainlyoccupiedwithhisGCduties.TheLCCwasrelievedfrom
GC by the developmental controller who had been training on LC. He observed N4252G high and
southofrunway35.WhentheLCCwenttoLCtorelievetheLCI,henoticedN4252Govertherunway
andstillhigh.Hecouldnotreallyestimatethealtitudeoftheaircraft,butitjustseemedhigh.Hewas
hoping that the pilot was not going to try to land because the aircraft was at leastmidfield and
lookedlikeitwasgoingtotouchdownatthefarendoftherunway.
TheLCCheardthepilotofN4252Greportthatshewasgoingaround.Shecommented:“thirdtime’sa
charm”.Hefeltconfidentthatshewascomfortablebasedonthatcomment.TheLCCtoldthepilotto
makea“close-inpattern”torunway4andthentoldherthathemighthavetoamendthatorperhaps
taketheaircrafttorunway35basedonothertraffic.
TUGrazIMasterthesis
HAppendix
H-8
The LCC then saw the aircraft “winging ... over” and “going steep”. He estimated N4252G was
probablyclosetoa90-degreebankbeforetheaircraftstartedto fall.Hetransmitted“Straighten it
out,straightenitout,”wantingthepilottolevelthewings,althoughtheairplanecrashed.Afterthe
accident,theLCCrecalledsomeonecallingonthefrequencyaskingaboutdeparture.TheLCCadvised
theFLMofwhathadhappenedwithN4252Gbutdidnotrecallthespecificsoftheconversation.
When asked about the “low and tight” instruction that he gave the pilot, he said he had given
instructions like that tootherpilotsbutdidnot recall the specifics.Hisplanwas tohave theCirrus
followa737ontherunway4final,soheaskedthepilottoreportthe737 insightandthenadded
thathemighthavetoputtheCirrusbackonrunway35.
TheLCCsaidapproachdoesaprettygoodjobonfinalandtheydon’t“jamthemuptoooften”. Ifa
generalaviationaircraftwentaround,hewouldprobablykeeptheaircraftratherthangiveitbackto
approach,anddependingontrafficwouldtaketheaircrafttorunway4orrunway35.Theflowinthis
case was to runways 4 and 35, so that was where he would have kept the Cirrus even with the
existingcrosswind.Theaircraftlookedhighduringbothapproachestorunway35.
TheFLMishissupervisor.TheLCCstatedthathehasnotbeentomanycrewbriefingsinthepastfew
years,andtheywerenotregularevents.Hedidrecallreceivingsometrainingonincidentsoccurring
atotherfacilities,butnotthespecificcontent(rf.(NTSB,AirTrafficControl,GroupChairman'sFactual
Report,CEN16FA211,2016,p.25,26)).
HOULCT-Controller
TheATCgroupinterviewedtheLCTonJune17,2016.
He began working for the FAA in December 2010 at the FAA Academy. After completing initial
training, he reported toDavidWayneHooks airport (DWH) inMarch 2010. The LCT transferred to
HOUinJanuary2016.HewasqualifiedontheFD/CDandGCpositions,andwastrainingontheLC,
helicopter,and localassistpositions.TheLCThasreceivedapproximately19hoursofOJTontheLC
position. He held an ATCmedical certificate. He had Saturday and Sunday off. On the day of the
accident,hewasworkinghisregularly-assignedshiftof07:00to15:00CDTandreceivingtrainingon
theLCpositionfromhissecondaryOJTI,hereincalledtheLCI.Hewasunsurehowlonghehadbeenon
positionbeforetheaccident.
TheLCTfirstbecameawareofN4252Gwhentheaircraftwaseightmileswestoftheairport.When
thepilotcalled,hewastalkingtohisinstructorandmissedthecallsign.Hethoughtthetransmission
wasfromaninboundSouthwestflight,soheclearedtheSouthwestjettolandbeforerealizingthat
N4252Ghadcheckedin.HethenclearedthepilotofN4252Gtoland.HenoticedthattheSouthwest
flight was overtaking N4252Gwhen the SWA flight was on approximately a 9mile final. The LCT
TUGrazIMasterthesis
HAppendix
H-9
instructedN4252G to flydirectly to thenumbersandkeep their speedup. Theapproach controller
calledataboutthesametimeandaskedthetowertohaveN4252Gflydirectlytotheairport.TheLCT
statedthataircraftspeedsonfinalcouldbeadjustedwithoutcoordinationwiththeI90Hobbyfinal
controller.HestatedthatN4252GandthefollowingSWAjetwereadvisedoftheovertakesituation.
TheLCTandhisOJTI (LCI)hadbeendiscussingwhether the spacingbetween the jetand theCirrus
wouldwork.WhenN4252Gwasbetweenoneandtwomilesfromrunway4,theOJTItookoverthe
frequency and instructed the pilot to go-around. Hewas unsurewhy the OJTI had taken over the
frequency insteadof simplyhavinghim issue the clearance.TheOJTI told thepilot toentera right
downwindforrunway35.TheLCTthentookthefrequencyback.HenoticedthatN4252Ghadgone
pasttherunway35finalandwasapproachingtherunway4final.Heinstructedthepilottoturnleft
heading030 tostayaway fromtraffic landingon runway4.Theheadingwasbasedonboth radar
andvisualobservationoftheaircraft’strack.
TheOJTItookthefrequencybackandissuedinstructionstothepilotinanattempttogettheaircraft
linedupwithrunway35.TheLCTstatedthattheOJTIadvisedN4252Gthattheyappearedtobetoo
highand issuedgo-around instructions.Onthenextapproachtorunway35,theaircraftwasagain
toohighandthepilotinitiatedago-around.Theaircraftappearedtobeaboutthesamealtitudeon
bothapproachestorunway35,anddefinitelytoohightoland.
TheFLMtoldtheLCTtorelievethegroundcontroller,sohemovedtotheGCposition,andtheLCC
tookover theLCposition.HeheardtheLCCsequenceN4252Gtorunway4.Hisattentionwasthen
divertedbyGCduties.HedidnotobserveN4252Gturn leftcrosswind,butsawtheaircraftwhen it
wasbetween50and75ftabovetheground.
TheFLMactivatedthecrashphone.Departureswerestoppedduetotheaccident,althougharrivals
continued to land. One of the airport fire trucks requested control of the discrete emergency
frequency.
TheLCTwasrelieved fromthegroundcontrolpositionabout15minutesafter theaccident.Aftera
ten-minutebreak,hereturnedtothetowertoworkgroundcontrol.
The LCT stated that he had not had any discussionswith anyone following the event. He had not
spokentotheeventcrisisteambutplannedtodoso.
OJTdebriefstookplaceaftereachtrainingsessionifwarranted,andwerenormallycompletedbythe
endofeachday.
The LCT stated the new procedural changes being implemented by the facility are good, such as
requiringadherencetostandardproceduresandminimizingrunwaychanges.
TheLCThadnotseenverymanygo-aroundsintraining.Theusualprocedurewasforjetstoproceed
straight down the runway, then turn to heading 160,maintain 3000 ft, and contact departure. In
TUGrazIMasterthesis
HAppendix
H-10
classroominstruction,controllersaretaughttotreatgo-aroundsasasatelliteairportdeparture.He
had not yet received any simulator training, although a simulator is available at Houston
Intercontinental. He noted that simulator training was not provided for the LC position, but was
providedaspartofGCtraining.Radartrainingwasprovidedviaonlinelearningmodules.
Based on his experience at DWH, the LCT was asked how he would characterize the handling of
N4252G’s arrival. Having the Cirrusmixed in with the jetsmeant that the situation needed to be
watched, but itwas not amajor issue. The pilot never sounded flustered or disoriented. After the
accident,theairportfirecrewsaskedtousefrequency120.2andrespondedtothefarNWcornerof
theairport.
TheLCTwasuncertainabout the typeof separationbeingappliedbetweentheSWAflightand the
Cirrusonfinal.Herealizedthatitwasnotgoingtoworkwhenhistrainertookovertheposition.The
intentwastopreventaflyoverontherunway(rf.(NTSB,AirTrafficControl,GroupChairman'sFactual
Report,CEN16FA211,2016,p.27,28)).
I90-ApproachController
TheATCgroupinterviewedtheI90–ApproachControllerviatelephoneonJune17,2016.
TheI90–ApproachControllerbeganworkingfortheFAAinOctober1989.HisfirstfacilitywasSan
Juancenter/approachcontrolinPuertoRico.BeforebeingassignedtoI90in2008,heworkedatIsla
GrandeATCT,SanJuanATCT,andSanJuanCenter.HeheldanATCmedicalcertificate.
Onthedateoftheaccident,hewasworkinghisregularly-assignedshiftof07:00to15:00CDT.
TheI90–ApproachControllerhadbeenworkingtheHobbyFinalpositionforabout45minuteswhen
he first became aware of N4252G. He recalled taking a handoff from the “Lakeside” sector when
N4252Gwasapproximately20mileswestofHOU.N4252Gcameinonabaselegtorunway4.The
aircraft’sgroundspeedwasabout130ktswithaheadwind.ThepilotofN4252Gsoundedconfident.
SomeofthearrivalsintoHOUwerebeingvectoredaroundheavyweathersouth-westoftheairport.
HesequencedN4252GbehindaBoeing737andgavethepilotawaketurbulenceadvisory.Atthat
point,thepilotseemedfine.TheI90–ApproachControllerhadothertrafficbehindN4252Gonfinal,
soheissuedtheaircraftaheadingtoshortentheapproachandswitchedtheaircrafttoHOUtower.
HeadvisedtheaircraftsequencedbehindN4252Gtoreducespeedto150ktsorlessandswitchedthe
aircrafttoHOUtower.AfterbothaircraftwereonHOUtowerfrequency,thespacingappearedtobe
diminishingbetweenN4252GandthetrailingB737.Theapproachcontrollerwasrequiredtocontinue
tomonitorspacingonfinalevenafteraircraftwereswitchedtothetower.Hewasworkingfiveorsix
otheraircraft,andnoticed thatN4252Gstill seemed tobeheaded toward theoutermarker, sohe
called the tower to have them turn the aircraft direct to the runway. N4252G showed a 120kts
TUGrazIMasterthesis
HAppendix
H-11
groundspeedtoabout3milefinal,thenstartedreducingspeed.Hetoldthenextjetarrivaltoreduce
speedto150kts,andtoldthepilottocontactthetower.
After N4252Gwent around on runway 4, the I90 – Approach Controller received a call fromHOU
toweraskinghimtoslowthenextarrivaltorunway4duetoN4252Glanding.Thefinalwasfairlyfull
out toabout20NM.The I90–ApproachControlleradvised theHOUcontroller thathewouldwork
N4252G,butHOUsaidtheywouldkeeptheaircraft.
TheI90–ApproachControllertoldthetowerhecouldnot issuethereduction,anddidnotslowthe
nextarrivalbecausetheaircraftwasalreadyatthefinalapproachfixandhedidnotthinkthatHOU
towercouldsequenceN4252Ginsideofthetraffic.HeswitchedthenextarrivaltoHOUtower.Hefirst
recognized that N4252G was landing runway 35 when he saw the aircraft turning final for that
runway,priortowhichhethoughtthetowerwasgoingtohaveN4252Glandonrunway4.
The I90 – Approach Controller said that HOU tower has control for speed changes of aircraft on
contact,withnorequirementforHOUtowertocoordinatethespeedchangeswithapproachcontrol.
Itisnormalpracticetorestrictarrivalsto170ktsonfinal.
Intheeventofago-aroundbyanaircraftoperatingunder instrumentflightrules,mostofthetime
thetowerwouldswitchtheaircraftbacktoapproach.IftheaircraftwasoperatingVFR,HOUtower
wouldusuallyworktheaircraftbackinforlanding.Iftheycouldnotdothat,thenI90wouldtakethe
go-aroundaircraftbackandre-sequenceitforanotherapproach.
TheI90–ApproachControllerwasfirstinformedabouttheaccidentbyanothercontrollerwhoheard
about it while on a break (rf. (NTSB, Air Traffic Control, Group Chairman's Factual Report,
CEN16FA211,2016,p.29,30)).
TUGrazIMasterthesis
IAppendix
I-1
APPENDIXI
SummaryofCFIStatements
ReferringtothepublisheddocumentintheNTSBDMScalled“CFIStatements”(2016),thecontentof
the informationfromtwoCFIs thathadflownwiththepilotofN4252G inthepast (in thiscontext
solelycalledthepilot)wassummarizedbytheauthorasfollows:
CFI-1:
Recentflightswiththepilot:September15,23and28,2015
These three flightswereconsidered the first flightsofher instrument training.Theyhadapre-and
post-flightdiscussionwithevery lesson.Specifically,before the lessononSeptember15,2015, they
talked about checklists, pre-flight, basic instrument control and reviewed the PAVE and IMSAFE
checklists.OnSeptember15,2015 theydidclimbs, turns,descents, instrumentscan,pre-andpost-
flightanddiscussedcollisionavoidanceandrunwayincursions.OnSeptember23,2015,theydidmore
of the sameandadded compass turns, timed turnsand introducedVORs.OnSeptember28, 2015,
theydidVORinterceptingandtracking.
NTSBaskedtheCFI-1whetherthesethreeflightscouldbeconsideredabiennialflightreview,which
wasansweredasno.
WhenaskedabouttheexperienceofCFI-1 intheCirrus, itwasansweredthattheCFI-1hadbeena
CirrusTrainedInstructorandhadover1100hoursofdualgiven,80hoursofwhichwasinaCirrus.
ThefinalquestionaskedwaswhethertheCFI-1hadseenthepilot inastressfulsituation.TheCFI-1
answeredthateverysituationinwhichtheyhadbeenwashandledbythepilotwithcomposureand
thecontrolof theairplanewasmaintained,comparablewithanystudentwithwhomtheCFI-1has
worked.
CFI-2:
Recentflightswiththepilot:onceonAugust4,2014andonceonSeptember24,2014
TheCFI-2flewwiththepilotonlytwiceafterbeingcertificated.Bothflightswererecurrenttraining
flights, but neither flight would complete the requirements of Title 14 CFR part 61.56 for a flight
review.
Regardingthepilot’sabilitytohandlestressfulenvironments,theCFI-2onlyflewahandfuloftimes,
and the few times when a stressful situation was observed the pilot handled it within acceptable
levelsandretainedcomposureandtheabilitytoflytheairplane.
TUGrazIMasterthesis
IAppendix
I-2
In terms of qualifications, the CFI-2 has been a Chief Instructor for a Cirrus Training Center, and a
qualifiedCirrusStandardizedInstructorPilot.TheexperienceoftheCFI-2is400hoursindualgivenin
Cirrus aircraft, 500 hours Cirrus total hours and 2900 hours overall (rf. (retrieved from
https://dms.ntsb.gov/pubdms/search/hitlist.cfm?docketID=60618&CFID=2395938&CFTOKEN=81732
fd00bba5423-5AB1BC7B-CB39-E91F-3732EB517FD2FBDB,CFIStatements,2016,p.1,2)).
TUGrazIMasterthesis
JAppendix
J-1
APPENDIXJ
RecordedFlightData
ReferringtotheNTSB,CockpitDisplay(s)–RecordedFlightData(2017)document,theGarminG1000
Integrated Flight Deck in N4252G included a data-logging feature. The SD memory card was
recoveredandingoodconditionandthedatarecordswereextracted.Itcontained820logfiles.The
accident flight recording was the last file recorded and it contained approximately 3hours and
10minutesofdatarecords.Additionally,aHeads-UpTechnologiesRDMdatarecorderwasmounted
in the tailof theaircraft,which isa lightweight impactand fire-hardened recorder. It is capableof
recordingapproximately150hoursofaircraftdataata rateofone recordper second.Each record
includesapproximately105positional,aircraftflightandengineparameters.Anexteriorexamination
revealed that the unit had not sustained any impact or heat/ fire damage. The unit powered up
normally and the recorded information was extracted using themanufacturer’s software, without
difficulty.
“The data extracted included 522220 total data records. The accident flight was the last session
recorded(approximately12000totaldatarecords(seconds))(rf.(NTSB,CockpitDisplay(s)-Recorded
FlightData,2017,p.2,3)).
For the STAMP (Leveson, 2011) modeling of this accident, the availability of flight data in an
electronic coded format supported the author in the analysis. For this reason, the data was
downloadedviatheDMSoftheNTSBwebsiteandanalysedindetail,inboththerawdatatablesand
subsequentlygraphicallyintheformofdiagrams.FordetailsrefertotheChapter2.2.
TUGrazIMasterthesis
KAppendix(SystemComponents)
K-1
APPENDIX(SYSTEMCOMPONENTS)KThis appendix provides basic descriptions of each individual system component, which was
consideredinmodelingoftheN4252Gaccident:
TrainingOrganisation
“Pilot training is availableon-site atmost airports in theUSA, either throughan FAA-certificated46
(approved) pilot school or through other47 training providers. […] Enrollment in an FAA-approved
pilot school usually ensures a high quality of training. Approved schools must meet prescribed
standardswith respect toequipment, facilities,personnel,andcurricula.However, individual flight
instructorsand trainingcompanies thatarenotcertificatedby theFAAas“pilot schools”mayalso
offerhighqualitytraining,butfindit impracticaltoqualifyforFAAcertification.Anotherdifference
between training provided by FAA-approved pilot schools and other providers is that fewer flight
hours are required to be eligible for a pilot certificate when the training is received through an
approvedschool”
(FAA.gov,retrievedfromhttps://www.faa.gov/training_testing/training/pilot_schools/,2019).
ATCControlService
“Air traffic control service is a service provided for the purpose of preventing collisions between
aircraft and on the manoeuvring area between aircraft and obstructions and for the purpose of
expeditingandmaintaininganorderlyflowofairtraffic”(ICAO,Annex11,2016,p.1-3).
AircraftManufacturer(Cirrus)
“AsofApril2018,thecompanyhaddeliveredover7,000SR-aircraftinnearly19yearsofproduction,
and has been theworld's largest producer of piston-powered aircraft since 2013” (Wikipedia.org,
retrievedfromhttps://en.wikipedia.org/wiki/Cirrus_Aircraft,2019).
COPA
“CirrusOwnersandPilotsAssociation (COPA) isanorganisation thatwelcomes themembershipof
Cirrus owners, pilots, and enthusiasts with an interest in aviation and Cirrus aircraft issues and
events. Three main training and safety related events provided by COPA are the Cirrus Pilot
46Author’snote:fordetails,refertoTitle14CFRpart141-PilotSchools47Author’snote:fordetails,refertoTitle14CFRpart61-CertificationPilots,FlightInstructors[…]
TUGrazIMasterthesis
KAppendix(SystemComponents)
K-2
Proficiency Program (CPPP), the Critical Decision Making (CDM) seminar, and the Partner in
Commandseminar.
TheCPPPisdesignedtoexposeCirruspilotstosituationstheymayencounterwhileoperatingtheir
aircraft. Topics such as weather, accident review, advanced avionics, emergency procedures, and
enginemanagementarediscussedandappliedduringaCPPP.
TheCDMseminar isafacilitatedinteractivehangar-flyingsessionwherethegrouplooksatgeneral
aviationandCirrusaccidentstatistics,reviewscasestudiesofCirrusaccidents,andparticipatesinthe
reenactmentofanactualaccident.
The Partner in Command seminar has been designed to give frequent Cirrus passengers more
knowledgeregardingsafetysystemoperationsintheunlikelyeventthatthepilotincommandshould
become incapacitated. Procedures include using basic radio communication and CAPS activation”
(FOM-SR20,2011,p.2-3,2-4).
HOUAirport
“William P. Hobby Airport […]HOU is an international airport in Houston. […]Hobby is Houston's
oldest commercial airport and was its primary commercial airport until Houston Intercontinental
Airport[…]opened”
(Wikipedia.org,retrievedfromhttps://en.wikipedia.org/wiki/William_P._Hobby_Airport,2019).
Operator/AircraftOwner
Itcouldnotbeverifiedunderwhichpre-requisitestheoperator/aircraftownerpermittedthepilot
tooperatetheaircraft.
Pilot
Forpersonaldetailsregardingthepilotoftheaccidentaircraft,refertoDAppendix.
Passengers
TheofficialNTSB accident report provided no details about the passengers on board the accident
aircraft.Recherches48by theauthorof this thesis revealedthat thepassengers (twomales,age52
and 27) were family members of the pilot, with the purpose of visiting a close relative who was
48Retrievedfromhttp://www.kathrynsreport.com/2016/06/cirrus-sr20-n4252g-safe-aviation-llc.htmlandhttps://www.dailymail.co.uk/news/article-3636188/Ma-ma-straighten-straighten-Tragic-words-woman-piloting-plane-husband-brother-filmed-crashing-killing-three.html
TUGrazIMasterthesis
KAppendix(SystemComponents)
K-3
receivingcancertreatmentinHouston(rf.(PassengerRecherches,2019)).Itcouldnotbeascertained
whetheranyofthepassengershadbeenalicensedpilotorpossessedpilot-relatedknowledge.
AircraftSR20
“TheCirrusSR20isanAmericanpiston-enginefour-or-five-seat,compositemonoplanebuiltbyCirrus
AircraftofDuluth,Minnesotasince1999.TheSR20wasthefirstproductiongeneralaviationaircraft
equipped with a parachute to lower the airplane safely to the ground after a loss of control,
structural failure or mid-air collision. It was also the first manufactured light aircraft with all-
composite construction and flat-panel avionics” (Wikipedia.org, retrieved from
https://en.wikipedia.org/wiki/Cirrus_SR20,2019).
TUGrazIMasterthesis
LAppendix(Illustrations)
L-1
APPENDIX(ILLUSTRATIONS)LFigure6-1illustratesaschematicoftheHOUAirport.
(HOU-ATCT-0064,2018,p.40)
Figure6-1HOUairportdiagram
TUGrazIMasterthesis
LAppendix(Illustrations)
L-2
Figure 6-2 illustrates the Guidance for establishing personal weather minimums for Cirrus Pilots,
whichwasretrievedfromSR20FlightOperationsManual(2011).
(FOM-SR20,2011,p.2-6)
Figure6-2GuidanceforestablishingPersonalWeatherMinimums
TUGrazIMasterthesis
LAppendix(Illustrations)
L-3
Figure6-3 illustrates theEnvelopeofSafety forCirrusPilots,whichwas retrieved fromSR20Flight
OperationsManual(2011).
(FOM-SR20,2011,p.2-7)
Figure6-3EnvelopeofSafety
TUGrazIMasterthesis
LAppendix(Illustrations)
L-4
Figure6-4 illustratesadiagram to calculate thewindcomponents,whichwas retrieved fromSR20
Pilot’sOperatingHandbook(2015).
(POH-SR20,2015,p.5-13)
Figure6-4Windcomponentdiagram
TUGrazIMasterthesis
MAppendix(ATCTranscript)
M-1
APPENDIX(ATCTRANSCRIPT)MThefollowingTable6-1summarizestheATCtransmissionsfromthefirstgo-arounduntiltheaccident
asretrievedfromHOUTowerAccidentPackageN4252G(2018).
CDT COM ATCTransmission/Note RY12:57:02 LCI “justgo-aroundandflyrunwayheadingfornow,maintainVFR,andI’mgoingtoputyouback
onthedownwindforrunway35.Thewindsare090at13gusts18.Canyouacceptrunway35?”4
12:57:15 52G “We’retogo-aroundandlineupforrunway35downwind” 35
12:57:20 LCI “N4252G,flyrunwayheadingforrunway4forrightnow” 35
12:57:23 52G “We'llflyrunwayheadingfor4,4252G” 35
12:57:34 LCI “N52Gwhenablegoaheadandmakearightdownwindnowforrunway35andthenwe’lljustgoaheadandkeepthatrightturn,runway35clearedtoland”
35
12:57:46 52G “OK,makearightdownwindforrunway35?” 35
12:57:50 LCI “N52Gyesandjustkeeptherightturnallthewayaround,you’rejustgoingtorollrightintothebaseforrunway35,clearedtoland.I’vegotanother737on5milefinaltorunway4andyou’regoingtobeinfrontofhim”
35
12:58:06 52G “...turningaroundforrunway35” 35
12:58:10 LCI “...justenterthedownwindforrunway35,”andthepilotacknowledged 35
12:58:16 LCI “I'llcallyourrightbasenow” 35
12:58:48 LCT “Cirrus52G737atyour2:00o’clockand3milesat900ftinboundforrunway4advisethattrafficinsight”
35
12:58:56 52G “Ihavetrafficsight,4252G” 35
12:58:58 LCT “52Gmakearightbasebehindthattrafficrunway35clearedtolandyou'regoingtobelandingthecrossingrunwaypriortoyourarrival”
35
12:59:07 52G “We'llmakearightbasefollowingthem4252Gfor35” 35
12:59:20 LCT “Cirrus52Gmakeaturnleftheading30degrees” 35
12:59:26 52G “Leftheading30degrees4252G” 35
12:59:30 LCIasksthepilotifshe,“...wantedtofollowthe737torunway4?” 35
12:59:35 52G “yesthatwouldbegreat,4252G” 35
12:59:38 LCI “Followthe737andtorunway4clearedtoland” 412:59:45 52G “AmIturningarightbasenow,4252G?” 4
12:59:48 LCI “N52Groger,justmaneuverbackforthestraight-in,Idon’tknowwhichwayyou’regoingnow,sojustturnbackaroundtorunway35”.
35
12:59:56 52G “Turningto35,I’msosorryfortheconfusion,4252G”. 35
13:00:00 LCI “That’sOK,we’llgetit” 35
13:00:13 LCI “Cirrus52Gwhichwayareyouturningnow?” 35
13:00:18 52G “IthoughtIwasturningarightbasefor35,4252G” 35
13:00:22 LCI “...that’sfine52G,uh,justmakeituh,yousayyou’reinarightturn,keepittight,Ineedyoutomakeittight”
35
13:00:29 52G “Keepingturntight,4252G” 35
13:00:31 LCI LCIprovidedatrafficalertto“0GA”abouttraffic1mileawayat900ft,whichwasN4252G.Thatpilotreportedthatshewas“looking”
35
13:00:37 LCI “N52GIneedyoutouhthereyougo,straightintorunway35,clearedtoland” 35
13:00:43 52G “Straightintorunway35andIdon’tbelieveI’mlinedupforthat” 35
13:00:49 LCI “Okay52Grogerturntotherightandclimbandmaintain1600,rightturn” 35
13:00:57 52G “1600rightturn4252G” 35
13:01:00 LCI “Yes,ma’am,headingabout040,which52Greadbackcorrectly 35
13:01:16 LCI “OK52G,let’sdothis.Canyoudoarightturnbacktojointhestraight-into35?Couldyoudoitlikethat?”
35
TUGrazIMasterthesis
MAppendix(ATCTranscript)
M-2
CDT COM ATCTransmission/Note RY13:01:25 52G “Yes,rightturnbackto35,N4252G” 35
13:01:29 LCI Thecontrollerinstructedthepilottomakearightturn,“allthewayaroundtorunway35,”andagainclearedthepilottoland.Thepilotacknowledged.
35
13:01:37 52G “35clearedtoland4252G”,repliedby52Gwith“thankyou”.Atthesametime,theHobbyFinalcontrollerwascallingthetowertoofferaspacetoputN4252Gbehindanotheraircraft,N4JJ,inboundontherunway4final.TheLCIcontrollerdidnotrespondtothatcall.
35
13:01:44 LCI N4JJcontactedthetoweronavisualapproachtorunway4.TheLCIcontrollertoldthepilottoreducetominimumspeed,andadvisedthathewouldbenumber2fortheairportfollowingaCirruson1milefinalforrunway35.ThepilotofN4JJacknowledgedtheinformation.
35
13:02:02 LCI “Cirrus52G,OK,you’relookinggoodjustcontinuearightturnforrunway35.Doyouseerunway35still?”
35
13:02:10 52G “Yes,35,4252Ghaveitinsight,continuingmyrollaround” 35
13:02:14 LCI “Yes,ma’am,yeahyou’regoodsoyoucanstartyourdescenttorunway35there,anduhclearedtolandon35”
35
13:02:21 52G “Clearedtolandon35,52G,thankyouverymuch” 35
13:02:25 LCI “Noproblemswindsareonezerozeroatonezero,I'msorrywindsareonezerozeroatonefiveguststotwozero”
35
13:02:30 52G “OKthankyou,tryingtolosealtitude,4252G” 35
13:02:38 LCI “Noproblem,littlebitofwindofftheright” 35
13:03:01 LCI “N52Gifyoudon’twanttoland–ifthat’stoohigh,wecanputyoubackaroundthedownwind,don’tforceitifyoucan’t”
35
13:03:08 52G “OK–we’llsee,thankyou,4252G” 35
13:03:28 LCI “OK,Ithinkyou’retoohigh,Cirrus52G,youmightbetoohigh” 35
13:03:32 52G “OK–we’llgo-aroundthen,N4252G” 35
13:03:44 LCI “Cirrus52G,roger,justuhokaymakeyou'rejustgoingtomakearighttrafficnowforrunway35we'llcomebackaroundandwegotitthistime”
35
13:03:53 52G “Soundsperfect,righttrafficforrunway35,4252G” 35
13:04:38 LCI thecontrollerclearedN4252Gtoland,stating,“...makerightdownwindtorunway35,andyouareclearedtoland–therewillbenoothertrafficforrunway4sothisonewillbeeasy”
35
13:04:48 52G “Makingrighttrafficfordownwindforrunway35,4252G” 35
13:04:53 LCI “...affirmative,andclearedtolandonrunway35viatherightdownwindandrightbase” 35
13:05:02 52G “Thankyou–rightdownwind,rightbase,runway35,4252G” 35
13:06:00 LCI “...there’sa737onshortfinalrunway4touchingdownrightinfrontofyousojustcautionwaketurbulencerightthereatthatintersection”
35
13:06:08 52G “OK,Igotthatinsight,N4252G” 35
13:07:01 ApositionreliefbriefingoccurredontheLCpositionandanewcontroller(LC)tookover. 35
13:07:03 LCI ThecontrolleraskedifthepilotofN4252Ghadrunway35insight. 35
13:07:07 52G “Runway35insight,4252G” 35
13:07:10 LCI “winds090at13gust18,runway35again,clearedtoland” 35
13:07:18 52G “35clearedtolandtryingtoget[laugh]downagain,4252G” 35
13:07:22 LCI “noproblem” 35
13:08:20 52G “4252G,goingaroundagain,thirdtimewillbeacharm” 35
13:08:25 LCC “OK,Cirrus52G,justgoaheadandmaketheleftturnnowtoenterthedownwind,midfielddownwindforrunway4,ifyoucanjustkeepitinanicetightlowpattern,I’mgoingtohavetraffic4milesbehindyousoIneedyoutojustkindofkeepitintightifyoucould”
35
13:08:41 52G “OK,thistimeI'llberunway4,turningleft,4252G” 4
13:08:45 LCC “YeahandactuallyImightendupsequencingyoubehindthattraffic,he’son4milesaminute,umitisgonnabeabittightwiththeonebehinditso,uh,whenyougetonthedownwind,stayonthedownwindandadvisemewhenyouhavethat737insight.We’lleitherdo4orwemightswingyouaroundto35uhuhma’am,ma’amuhstraightenupstraightenup!”
4
(HOU-ATCT-0064,2018,p.44-49)
Table6-1SummaryofATCtransmissions,12:57:02-13:08:45CDT