Fatigue-is-a-risk-factor-for-flight-performance.docx

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1、Fatigueisariskfactorforflightperformanceandsafetyincommercialaviation.InUScommercialavi-ation,tohelptocurbfatigue,themaximumdurationofflightdutyperiodsisregulatedbasedonthescheduledstarttimeandthenumberofflightsegmentstobeflown.Thereisscientificsupportforregu-latingmaximumdutydurationbasedonschedule

2、dstarttime;fatigueiswellestablishedtobemodulatedbycircadianrhythms.However,ithasnotbeenestablishedscientificallywhetherthenumberofflightsegments,perse,affectsfatigue.Toaddressthissciencegap.weconductedarandomized,counterbalanced,cross-overstudywith24active-dutyregionalairlinepilots.Objectiveandsubje

3、ctivefatiguewascomparedbetweena9-hordutydaywithmultipletake-offsandlandingsversusadutydayofequaldurationwithasingletake-offandlanding.Tostandardizeexperimentalconditionsandisolatethefatiguingeffectofthenumberofsegmentsflown,theentiredutyscheduleswerecarriedoutinahigh-fidelity,moving-base,full-flight

4、,regionaljetflightsimulator.Stepsweretakentomaintainoperationalrealism,includingsimulatedair-planeinspectionsandacceptancechecks,useofrealisticdispatchreleasesandairportcharts,real-worldairtrafficcontrolinteractions,etc.Duringeachofthetwodutydays,10fatiguetestboutswereadmiis-tered,whichincludeda10-m

5、inutePsychomotorVigilanceTest(PVT)assessmentofobjectivefatigueandSamn-Perelli(SP)andKarolinskaSleepinessScale(KSS)assessmentsofsubjectivesleepiness-fatigue.Resultsshowedagreaterbuild-upofobjectiveandsubjectivefatigueinthemulti-segmentdutydaythaninthesingle-segmentdutyday.Withdutystarttimeandduration

6、andothervariablesthatcouldimpactfatiguelevelsheld11stant.thegreaterbuild-upoffatigueinthemulti-segmentdutydaywasattributablespecificallytothedifferenceinthenumberofflightsegmentsflown.Comparedtofindingsinpreviouslypublishedlaboratorystudiesofsimulatednightshiftsandnighttimesleepdeprivation,themagnit

7、udeofthefatiguingeffectofthemultipletake-offsandlandingswasmodest.Ratingsofflightperformancewerenotsignificantlyreducedforthesimulatedmulti-segmentdutyday.TheUSdutyandflighttimeregulationsforcommercialaviationshortenthemaximumdutydurationinmulti-segmentoperationsbyupto25%dependingfunctionoftimeawake

8、(Daanetal.,1984;Dijketal.,1992).Thecircadianandhomeostaticprocessesinteracttogeneratepredictabledielpat-ternsoffatigue(DijkandCzeisler,1994;GabehartandVanDongen,inpress),wherethetermfatiguereferstosleepinessandperfor-manceimpairment(asiscommonpracticeinoperationalsettings;seeSatterfieldandVanDongen,

9、2013).Inthiscontext,regulatingmaximumdutydurationsasafunctionofstarttimetohelpmitigatefatigueandimprovesafetymakessense(VanDongenandHursh12010),especiallyindaytime-orientedoperations(additionalcom-plexitieslimittheeffectivenessofsuchregulationsinnighttimeoperations;e.g.,seeRanganetal.,2013).Thefatig

10、uesciencepertainingtonumberofsegmentsflownisnotaswelldeveloped.Mostoftheliteratureonaviationandfatiguehasfocusedonlong-rangeandultra-long-rangeflights(Holmesetal.,2012;Ganderetal.,2014)ratherthanshort-range,multi-segmentoperations.1.imitedevidencepertainingtoshort-rangeflightoperationscomesfromfield

11、studies,inwhichpilotssub-jectiveratingsoffatiguewerefoundtoincreasewiththenumberofsegmentsflowninthedutyperiod(Powelletal.,2007,2008).Inthesestudies,dutyschedulesandoperationalconditionswerenotstandardized,leavingtoomanypotentialconfoundstobeabletodrawconclusionsregardingthefatiguingeffectofflyingmu

12、l-tiplesegmentsperse.Noobjectivedatapertainingtofatigueinmulti-segment,short-rangeoperationshavebeenpublished.Still,itstandstoreasonthattheremaybeafatiguingeffectofflyingmultiplesegmentsinadutyday-inparticular,afatiguingeffectofmultipletake-offsandlandings.Thesecriticalphasesofflightarearguablythemo

13、stsafety-sensitive,andtheytypicallyhavethehighesttaskload(Hoermannetal.,2015).Asystemsbiologyviewofthebrainmechanismsunderlyingcognitiveimpairmentduetofatigue(VanDongenetal.,2011a)positsthattheeffectoffatigueonalertnessandperformanceiseuroalcircuituse-dependent,andisthuspredictedtobeafunc-tionoftask

14、load.Thispredictionhasbeenconfirmedinlaboratorystudies,whichhaveshownthatincreasedtaskloadacceleratesthedegradationofsubjectivealertnessandcognitiveperformanceduetocircadianrhythmandsleeploss(VanDongenandDinges,2007;Goeletal.,2014).Yet,theeffectofincreasedtaskloadonalertnessandperformanceinthelabora

15、toryappearstobemodestinmag-nitde.anditisaprioriuncleartowhatextentittranslatestoasignificanteffectofmultipletake-offsandlandingsinreal-worldoperations.Theobjectiveofthepresentstudywastohelpfillthissciencegap.Inactive-dutyregionalairlinepilots,wecomparedtheeffectoffatigueonalertnessandperformancebetw

16、eenadutyschedulecontainingmultiplesegmentsandadutyschedulentainingonlyasinglesegment.Dutystarttimeanddurationwereheldconstant,andtheorderofconditionswasrandomizedandcounterbalanced,withpilotsservingastheirowncontrols.Thedutyperiodswerecarriedoutusingahigh-fidelity,moving-base,full-flightsimla-tor.Thisenabledustostandardizeandaccountforotherfatiguefactorscommonlyencounteredinreal-worldcommercialaviation(e.g.,airtrafficdensity,weather,scheduledelays),whileretainingahighdegreeo