8. frms implementation guide ~ draft

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1stEdition:2011

Fatigue Risk Management

Systems (FRMS)

Implementation Guide


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NOTE

DISCLAIMER. The information contained in this publication is subject to constant review in the light

of changing government requirements and regulations. No subscriber or other reader should act on the

basis of any such information without referring to applicable laws and regulations and without taking

appropriate professional advice. Although every effort has been made to ensure accuracy, the

International Air Transport Association (IATA), and the International Civil Aviation Organization

(ICAO) shall not be held responsible for any loss or damage caused by errors, omissions, misprints or

misinterpretation of the contents hereof. Furthermore, the International Air Transport Association and

the International Civil Aviation Organization expressly disclaim any and all liability to any person or

entity, whether a purchaser of this publication or not, in respect of anything done or omitted, and the

consequences of anything done or omitted, by any such person or entity in reliance on the contents of

this publication.

Opinions expressed in this publication do not necessarily reflect the opinion of the International AirTransport Association. The mention of specific companies, products in this publication does not imply

that they are endorsed or recommended by the International Air Transport Association in preference

to others of a similar nature which are not mentioned.

International Air Transport Association 2011. All Rights Reserved. No part of this publication may be

reproduced, recast, reformatted or transmitted in any form by any means, electronic or mechanical,

including photocopying, recording or any information storage and retrieval system, without the prior

written permission from:

Senior Vice President

Safety, Operations and Infrastructure

International Air Transport Association

800 Place Victoria, P.O. Box 113

Montral, Qubec


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IATA/ICAOFRMSImplementationGuideforOperators

NOTE:

ThisguideisajointdocumentcreatedthroughICAO/IATA collaboration

ThisdocumenthasbeenapprovedbyIATAbutisyettobeapprovedbyICAOCouncilandisthereforesubject

tochange.

Thisdocumentisstillindraftform(preproduction)~somefootnotes,numberingmaybeincorrect

Thisdocumentcontainscontentonly:prefaceandendorsementsarenotyetincluded

Thisdocument,oncecomplete,willbeavailableonlinefreeofcharge


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ContentsIATAFRMSImplementationGuide...........................................................................................................................1

ChapterOne:IntroductiontoFatigueRiskManagementSystems(FRMS) .............................................................7

1.1 WhatisaFatigueRiskManagementSystem?..........................................................................................7

1.2WhytheAviationIndustryisIntroducingFRMS.............................................................................................8

1.3 ICAORequirementsforFatigueRiskManagementSystems....................................................................9

1.4StructureofthisManual...............................................................................................................................12

ChapterTwo:ScienceforFRMS .............................................................................................................................15

2.1IntroductiontoScienceforFRMS.................................................................................................................15

2.2EssentialSleepScience.................................................................................................................................15

2.2.1WhatisHappeningintheBrainDuringSleep .......................................................................................15

2.2.2

The

Issue

of

Sleep

Quality .....................................................................................................................19

2.2.3ConsequencesofNotGettingEnoughSleep.........................................................................................21

2.3IntroductiontoCircadianRhythms ..............................................................................................................24

2.3.1ExamplesofCircadianRhythm..............................................................................................................24

2.3.2TheCircadianBodyClockandSleep......................................................................................................26

2.3.3SensitivityoftheCircadianBodyClocktoLight ....................................................................................28

2.3.4ShiftWork..............................................................................................................................................29

2.3.5JetLag ....................................................................................................................................................31

2.4SummaryofEssentialScienceforFRMS ......................................................................................................35

ChapterThree:FRMSPolicyandDocumentation..................................................................................................46

3.1IntroductiontoFRMSPolicyandDocumentation........................................................................................46

3.2FRMSPolicy ..................................................................................................................................................47

3.2.1ScopeoftheFRMS.................................................................................................................................47

3.3.2ThingsthattheFRMSPolicyMustCover ..............................................................................................48

3.3ExamplesofFRMSPolicyStatements ..........................................................................................................49

3.3.1FRMS

Policy

Statement

for

aMajor

Air

Carrier.....................................................................................50

3.3.2FRMSPolicyStatementforaSmallerOperatorProvidingMedicalEvacuationServices......................51

3.4 FRMSDocumentation.............................................................................................................................52

3.4.1ExampleofTermsofReferenceforaFatigueSafetyActionGroup......................................................53

ChapterFour:FatigueRiskManagement(FRM)Processes ...................................................................................55

4.1IntroductiontoFRMProcesses ....................................................................................................................55


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4.2FRMProcessesStep1:IdentifytheOperationsCovered.............................................................................59

4.3FRMProcessesStep2:GatherInformationandAdditionalDataifNeeded................................................59

4.4FRMProcessesStep3:HazardIdentification...............................................................................................62

4.4.1PredictiveHazardIdentificationProcesses ...........................................................................................62

4.4.2ProactiveHazardIdentificationProcesses ............................................................................................65

4.4.3ReactiveHazardIdentificationProcesses..............................................................................................71

4.5FRMProcessesStep4:RiskAssessment ......................................................................................................72

4.6FRMProcessesStep5:RiskMitigation.........................................................................................................74

4.7Example:SettingupFRMProcessesforANewULRRoute..........................................................................78

4.7.1:Step1IdentifytheOperation............................................................................................................78

4.7.2:Step2GatherandAnalyzeAvailableInformation ............................................................................78

4.7.3:Step3IdentifyHazards......................................................................................................................81

4.7.4:Step4AssessSafetyRisk ...................................................................................................................82

4.7.5:Step5SelectandImplementControlsandMitigations....................................................................82

4.7.5:Step6MonitorEffectivenessofControlsandMitigations ...............................................................83

4.7.6:LinkingtoFRMSSafetyAssuranceProcesses.......................................................................................83

ChapterFive:FRMSSafetyAssuranceProcesses ...................................................................................................85

5.1IntroductiontoFRMSSafetyAssuranceProcesses ......................................................................................85

5.2FRMSSafetyAssuranceProcessesStep1:CollectandReviewData ...........................................................89

5.3FRMSSafetyAssuranceProcessesStep2:EvaluateFRMSPerformance.....................................................91

5.4FRMSSafetyAssuranceProcessesStep3:IdentifyEmergingHazards ........................................................92

5.5FRMSSafetyAssuranceProcessesStep4:IdentifyChangesAffectingFRMS..............................................93

5.6FRMSSafetyAssuranceProcessesStep5:ImproveEffectivenessofFRMS ................................................94

5.7AssigningResponsibilityforFRMSSafetyAssuranceProcesses ..................................................................94

5.8ExamplesofFRMSSafetyAssuranceProcessesInteractingWithFRMProcesses.......................................95

ChapterSix:FRMSPromotionProcesses .............................................................................................................104

6.1 IntroductiontoFRMSPromotionProcesses ........................................................................................104

6.2 FRMSTrainingPrograms ......................................................................................................................106

6.2.1 WhoNeedstobeTrained.............................................................................................................106

6.2.2 Curriculum ....................................................................................................................................106

6.2.3FRMSTrainingFormatsandFrequency...............................................................................................110

6.2.3 FRMSTrainingEvaluation.............................................................................................................110

6.2.5 FRMSTrainingDocumentation.....................................................................................................111


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6.3 FRMSCommunicationsPlan.................................................................................................................111

ChapterSeven:FRMSImplementation ................................................................................................................1 13

7.1 IntroductiontoFRMSImplementation ................................................................................................113

7.2 PhaseI:Planning...................................................................................................................................114

7.3 PhaseII:ImplementReactiveFRMProcesses......................................................................................115

7.4 PhaseIII:ImplementProactiveandPredictiveFRMProcesses ...........................................................115

7.5 PhaseIV:ImplementFRMSSafetyAssuranceProcesses .....................................................................116

7.6 OperationalExampleofStagedFRMSImplementation.......................................................................116

AppendixA:Glossary............................................................................................................................................119

AppendixB:MeasuringCrewmemberFatigue ....................................................................................................124

B1 CrewmembersRecallofFatigue..........................................................................................................125

B1.1 FatigueReportingForms ..................................................................................................................125

B1.2 RetrospectiveSurveys ......................................................................................................................127

B2 MonitoringCrewmemberFatigueDuringFlightOperations ...............................................................128

B2.1 SubjectiveFatigueandSleepinessRatings.......................................................................................128

B2.2 ObjectivePerformanceMeasurement.............................................................................................132

B2.3 MonitoringSleep ..............................................................................................................................133

B2.4 MonitoringtheCircadianBodyClockCycle .....................................................................................140

B3 EvaluatingtheContributionofFatiguetoSafetyEvents .....................................................................142

AppendixC:ProceduresforControlledRestontheFlightDeck..........................................................................148


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ChapterOne:IntroductiontoFatigueRiskManagementSystems(FRMS)

The

purpose

of

this

FRMS

Implementation

Guide

is

to

provide

air

operators

with

information

for

implementing

anFRMSthatisconsistentwithICAOStandardsandRecommendedPractices(SARPs).AstheICAOprovisionsforFRMSevolve,everyeffortwillbemadetokeepthismanualuptodate.However,itisrecommendedthatoperators check the current SARPs to find out if anything important has changed since this version of themanualwasdeveloped.OperatorsalsoneedtoensurethattheirFRMSmeetstherequirementsoftheirStatesregulatoryauthority.

AvarietyofoptionstoaddresstheICAOStandardsforanFRMSarepresentedthroughoutthisguide.Thesecanbeadaptedtotheneedsofdifferentsizesandtypesofoperators (international,domestic,passenger,cargo,etc)andtospecificoperations(UltraLongRange(ULR),longhaul,shorthauldomestic,oncall/charter,etc). Itis not necessary to implement all of these options to have an effective FRMS that meets regulatoryrequirements.

1.1WhatisaFatigueRiskManagementSystem?Crewmemberfatiguecanbedefinedas:

Aphysiological state of reducedmental orphysicalperformance capability resultingfrom sleep loss or

extendedwakefulness, circadianphase, orworkload (mental and/orphysical activity) that can impair a

crewmembersalertnessandabilitytosafelyoperateanaircraftorperformsafetyrelatedduties.

Fatigueisamajorhumanfactorshazardbecauseitaffectsmostaspectsofacrewmembersabilitytodotheirjob.ICAOdefinesaFatigueRiskManagementSystem(FRMS)as:

Adatadrivenmeansof continuouslymonitoringandmanagingfatiguerelated safety risks,basedupon

scientific principles and knowledge as well as operational experience that aims to ensure relevant

personnelareperformingatadequatelevelsofalertness.

AnFRMSaims to ensure that flight andcabincrew members aresufficientlyalertso theycan operate toasatisfactorylevelofperformance. ItappliesprinciplesandprocessesfromSafetyManagementSystems(SMS)1tomanagethespecificrisksassociatedwithcrewmemberfatigue. LikeSMS,FRMSseekstoachievearealisticbalance between safety, productivity, and costs. It seeks to proactively identify opportunities to improveoperationalprocessesandreducerisk,aswellasidentifyingdeficienciesafteradverseevents.ThestructureofanFRMSasdescribedhereismodelledontheSMSframework.Thecoreactivitiesaresafetyriskmanagement(described in the SARPS as FRM processes) and safety assurance (described in the SARPs as FRMS safetyassuranceprocesses).ThesecoreactivitiesaregovernedbyanFRMSpolicyandsupportedbyFRMSpromotionprocesses,andthesystemmustbedocumented.

BothSMSandFRMSrelyontheconceptofaneffectivesafetyreportingculture1,wherepersonnelhavebeentrainedandareconstantlyencouragedtoreporthazardswheneverobservedintheoperatingenvironment.To

1 SeeICAOSafetyManagementManual(Doc9859)andIATAIntroductiontoSafetyManagementSystems(SMS),2nd

Edition.


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encourage the reporting of fatigue hazards by all personnel involved in an FRMS, an operator must clearlydistinguishbetween:

unintentionalhumanerrors,whichareacceptedasanormalpartofhumanbehaviorandarerecognizedandmanagedwithintheFRMS;and

deliberateviolationsofrulesandestablishedprocedures.AnoperatorshouldhaveprocessesindependentoftheFRMStodealwithintentionalnoncompliance.

Toencourageanongoingcommitmentbypersonneltoreportingfatiguehazards,theorganizationmusttakeappropriate action in response to those reports. When an effective safety reporting system exists, a largepercentageofsafetyreportsfromoperationalpersonnelrelateto identifiedorperceivedhazards, insteadoferrorsoradverseevents.

1.2WhytheAviationIndustryisIntroducingFRMSThe traditional regulatory approach to managing crewmember fatigue has been to prescribe limits onmaximumdaily,monthly,andyearlyflightanddutyhours,andrequireminimumbreakswithinandbetween

dutyperiods.Thisapproachcomesfromalonghistoryoflimitsonworkinghoursdatingbacktotheindustrialrevolution.Itenteredthetransportationsectorintheearly20thcenturyinaseriesofregulationsthatlimitedworking hours in rail, road and aviation operations2. The approach reflects early understanding that longunbrokenperiodsofworkcouldproducefatigue(nowknownastimeontaskfatigue),andthatsufficienttimeisneededtorecoverfromworkdemandsandtoattendtononworkaspectsoflife.

Inthesecondhalfofthe20thcentury,scientificevidencebeganaccumulatingthatimplicatedothercausesoffatigue in addition to timeontask, particularly in 24/7 operations. The most significant new understandingconcerns:

thevital importanceofadequatesleep (notjustrest)forrestoringandmaintainingallaspectsofwaking

function;and

dailyrhythmsintheabilitytoperformmentalandphysicalwork,andinsleeppropensity(theabilitytofallasleepandstayasleep),thataredrivenbythedailycycleofthecircadianbiologicalclockinthebrain.

This new knowledge is particularly relevant in the aviation industry which is unique in combining 24/7operationswithtransmeridianflight.

Inparallel,understandingofhumanerroranditsroleinaccidentcausationhasincreased.Typically,accidentsand incidents result from interactionsbetweenorganizationalprocesses (i.e. workplaceconditions that leadcrewmemberstocommitactivefailures),andlatentconditionsthatcanpenetratecurrentdefensesandhaveadverseeffectsonsafety1.TheFRMSapproachisdesignedtoapplythisnewknowledgefromfatiguescienceand safetyscience. It is intended to providean equivalent, or enhanced, level of safety, while alsoofferinggreateroperationalflexibility.

Prescriptiveflightanddutytimelimitsrepresentasomewhatsimplisticviewofsafetybeinginsidethelimitsissafewhilebeingoutsidethelimitsisunsafeandtheyrepresentasingledefensivestrategy.Whiletheyare

2GanderPH,HartleyL,PowellD,CabonP,HitchcockE,MillsA.PopkinS(2010).FatigueriskmanagementI:organizational

factors.AccidentAnalysisandPrevention(inpress).


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Prescriptiveflightand

dutytimelimitations

Addressestransientandcumulativefatigue Sharedoperatorindividualresponsibility

SMS

Effectivesafetyreporting Seniormanagementcommitment Continuousmonitoringprocess Investigationofsafetyoccurrences Sharingofinformation Integratedtraining EffectiveimplementationofSOPs Continuousimprovement

However,anFRMS,asamanagementsystem focusedon fatigue,alsohasadded requirementsbeyond thatwhich would be expected of an operator complying with prescriptive flight and duty time limitations andmanaging their fatiguerisks through theirSMS. InmeetingtheseadditionalFRMSspecificrequirements,anoperatorwithanapprovedFRMSmaymoveoutsidetheprescribedlimits. Therefore,thefatiguemanagementSARPs in Section 4.10, Annex 6, Part I, include particular Standards that enable the effective regulation ofFRMS.

The following text box contains the SARPs in Annex 6 Part I that relate to Fatigue Management. States arerequiredtohaveregulationsforprescriptiveflightanddutytimelimitations,buttheyalsohavetheoptiontoestablishFRMSregulations. Inaddition,there isarequirementthatwhenFRMS isused,operationsmanualsreflecttheFRMSoption(Annex6,PartI,Appendix2).

Appendix8hasbeenaddedtoAnnex6,PartItogivedetailedrequirementsforanFRMSwhichmustinclude,ataminimum,thefollowingcomponents.

1. FRMSpolicyanddocumentation;2. Fatigueriskmanagementprocesses;3. FRMSsafetyassuranceprocesses;and4. FRMSpromotionprocesses.

Table1.1showshowthesecomponentsmaptotherequirementsofSMS. Annex6,PartI,recommendsthat,whereanoperatorhasanFRMS,itisintegratedwiththeoperatorsSMS.


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Annex6PartI

4.10FatigueManagement

4.10.1 TheStateoftheOperatorshallestablishregulationsforthepurposeofmanagingfatigue.Theseregulationsshallbebaseduponscientificprinciplesandknowledge,withtheaimofensuringthatflightandcabincrewmembersareperformingatanadequatelevelofalertness.Accordingly,theStateoftheOperatorshallestablish:

a) regulationsforflighttime,flightdutyperiod,dutyperiodandrestperiodlimitations;andb) whereauthorizinganoperatortouseaFatigueRiskManagementSystem(FRMS)tomanagefatigue,FRMS

regulations.

4.10.2 TheStateoftheOperatorshallrequirethattheoperator,incompliancewith4.10.1andforthepurposesofmanagingitsfatiguerelatedsafetyrisks,establisheither:

a) flighttime,flightdutyperiod,dutyperiodandrestperiodlimitationthatarewithintheprescriptivefatiguemanagementregulationsestablishedbytheStateoftheOperator;or

b) aFatigueRiskManagementSystem(FRMS)incompliancewith4.10.6foralloperations;orc) anFRMSincompliancewith4.10.6forpartofitsoperationsandtherequirementsof4.10.2a)fortheremainderof

itsoperations.

4.10.3 Wheretheoperatoradoptsprescriptivefatiguemanagementregulationsforpartorallofitsoperations,theStateoftheOperatormayapprove,inexceptionalcircumstances,variationstotheseregulationsonthebasisofariskassessmentprovidedbytheoperator.Approvedvariationsshallprovidealevelofsafetyequivalentto,orbetterthan,thatachievedthroughtheprescriptivefatiguemanagementregulations.

4.10.4 TheStateoftheOperatorshallapproveanoperatorsFRMSbeforeitmaytaketheplaceofanyoralloftheprescriptivefatiguemanagementregulations.AnapprovedFRMSshallprovidealevelofsafetyequivalentto,orbetterthan,theprescriptivefatiguemanagementregulations.

4.10.5 StatesthatapproveanoperatorsFRMSshallestablishaprocesstoensurethatanFRMSprovidesalevelofsafetyequivalentto,orbetterthan,theprescriptivefatiguemanagementregulations.Aspartofthisprocess,theStateoftheOperatorshall:

a) requirethattheoperatorestablishmaximumvaluesforflighttimesand/orflightdutyperiods(s)andduty

period(s),andminimumvaluesforrestperiods.Thesevaluesshallbebaseduponscientificprinciplesandknowledge,subjecttosafetyassuranceprocesses,andacceptabletotheStateoftheOperator;

b)mandateadecreaseinmaximumvaluesandanincreaseinminimumvaluesintheeventthattheoperatorsdataindicatesthesevaluesaretoohighortoolow,respectively;and

c) approveanyincreaseinmaximumvaluesordecreaseinminimumvaluesonlyafterevaluatingtheoperatorsjustificationforsuchchanges,basedonaccumulatedFRMSexperienceandfatiguerelateddata.

4.10.6 WhereanoperatorimplementsanFRMStomanagefatiguerelatedsafetyrisks,theoperatorshall,asaminimum:a) incorporatescientificprinciplesandknowledgewithintheFRMS;b) identifyfatiguerelatedsafetyhazardsandtheresultingrisksonanongoingbasis;c) ensurethatremedialactions,necessarytoeffectivelymitigatetherisksassociatedwiththehazards,are

implementedpromptly;d) provideforcontinuousmonitoringandregularassessmentofthemitigationoffatiguerisksachievedbysuch

actions;ande) provideforcontinuousimprovementtotheoverallperformanceoftheFRMS.

4.10.7 Recommendation.Statesshouldrequirethat,whereanoperatorhasanFRMS,itisintegratedwiththeoperatorsSMS.

4.10.8 Anoperatorshallmaintainrecordsforallitsflightandcabincrewmembersofflighttime,flightdutyperiods,dutyperiods,andrestperiodsforaperiodoftimespecifiedbytheStateoftheOperator.


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Table1.1ComparingSMSandFRMSComponents

SMSFramework FRMS

1. Safetypolicyandobjectives 1. FRMSpolicyanddocumentation

2. Safetyriskmanagement 2. FRMprocesses Identificationofhazards Riskassessment Riskmitigation

3. Safetyassurance 3. FRMSsafetyassuranceprocesses FRMSperformancemonitoring Managementofoperationalandorganisational

change ContinuousFRMSimprovement

4. Safetypromotion 4. FRMSpromotionprocesses Trainingprograms FRMScommunicationplan

ThecoreoperationalactivitiesoftheFRMSaretheFRMprocessesandtheFRMSsafetyassuranceprocesses.TheyaresupportedbyorganizationalarrangementsdefinedintheFRMSpolicyanddocumentation,andbytheFRMSpromotionprocesses.

1.4StructureofthisManualFigure 1.1 shows a basic framework linking the required components of an FRMS. For ease of explanation,Figure 1.1 presents a single, central, functional group, designated as the Fatigue Safety Action Group,

responsibleforalloftheseFRMScomponents. TheFatigueSafetyActionGroupincludesrepresentativesofallstakeholdergroups (management,scheduling,andcrewmembers)andother individualsasneededtoensurethat ithasappropriateaccesstoscientificandmedicalexpertise. However,dependingontheorganizationalstructure,someoftheFatigueSafetyActionGroupfunctionsasdescribedinthismanualmaybeundertakenbyothergroupswithintheorganization(discussedfurtherinChapter3). Theimportantthingisthat,irrespectiveofwhodoesthem,allofthecomponentfunctionsrequiredunderanFRMSbeperformed.


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Figure1.1:LinkingtherequiredcomponentsofanFRMS

The Fatigue Safety Action Group coordinates the FRM processes (the daytoday fatigue risk managementactivities). The FRMS safety assurance processes monitor how well the FRMS is functioning from a systemperspective.TheyalsoprovideinputforadaptingtheFRMStomeetchangingoperationaldemandsandforitscontinuousimprovement.

Communicationbetween theFRMSprocessesand theSMS (inbothdirections) isnecessary to integrate themanagementofthefatiguerisksintothebroaderriskmanagementactivitiesoftheSMS.

The detailed structure of an FRMS, and the specific ways in which it links to an operators SMS, will varyaccordingto:

thesizeoftheorganization; thetypeandcomplexityoftheoperationsbeingmanaged; therelativematurityoftheFRMSandtheSMS;and therelativeimportanceofthefatiguehazards.

TheFRMS

approach

isbased

onapplying

scientific

principles

and

knowledge

to

manage

crewmember

fatigue.

ChapterTwointroducestheessentialscientificconceptsthatareneededtodevelopandimplementanFRMS.

ChaptersThree,Four,Five,andSixeachdealwithoneoftherequiredFRMScomponents.ChapterSevensteps

thoughastagedapproachforimplementinganFRMS.

AppendicesA,BandCprovideextrainformationtosupportthatprovidedintheprecedingchapters. Forease

ofreference,AppendixAprovidesaglossaryoftermsusedinthismanual. AppendixBprovidesmoredetailed

information on methods of measuring fatigue as part of the FRM processes presented in Chapter Three.


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AppendixCalsosupportsChapterThreebyprovidingfurtherinformationontheuseofcontrolledrestonthe

flightdeckasamitigatoroffatiguerisk.


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ChapterTwo:ScienceforFRMS

2.1IntroductiontoScienceforFRMSThe FRMS approach represents an opportunity for operators to use advances in scientific knowledge toimprove safety and increase operational flexibility. This chapter reviews the scientific principles needed todevelopandimplementaneffectiveFRMS.

InChapterOne,theICAOdefinitionofcrewmemberfatiguewasgivenas:

Aphysiological state of reducedmental orphysicalperformance capability resultingfrom sleep loss or

extendedwakefulness, circadianphase, orworkload (mental and/orphysical activity) that can impair a

crewmembersalertnessandabilitytosafelyoperateanaircraftorperformsafetyrelatedduties.

Inflightoperations,fatiguecanbemeasuredeithersubjectivelybyhavingcrewmembersratehowtheyfeel,orobjectivelybymeasuringcrewmembersperformance(ChapterFourandAppendixB).

Anotherwayofthinkingaboutthisisthatfatigueisastatethatresultsfromanimbalancebetween:

thephysicalandmentalexertionofallwakingactivities(notonlydutydemands);and recoveryfromthatexertion,which(exceptforrecoveryfrommusclefatigue)requiressleep.

Following this line of thinking, to reduce crewmember fatigue requires reducing the exertion of wakingactivitiesand/orimprovingsleep.TwoareasofsciencearecentraltothisandarethefocusofthisChapter.

1. Sleepscienceparticularlytheeffectsofnotgettingenoughsleep(ononenightoracrossmultiplenights),andhowtorecoverfromthem;and

2. Circadianrhythmsthestudyofinnaterhythmsdrivenbythedailycycleofthecircadianbiologicalclock(apacemakerinthebrain).Theseinclude: rhythmsinsubjectivefeelingsoffatigueandsleepiness;and rhythms intheabilitytoperformmentalandphysicalwork,whichaffecttheeffortrequiredtoreach

anacceptablelevelofperformance(exertion);and rhythmsinsleeppropensity(theabilitytofallasleepandstayasleep),whichaffectrecovery.

2.2EssentialSleepScienceThere isawidespreadbelief thatsleep timecanbe tradedoff to increase theamountof timeavailable forwakingactivitiesinabusylifestyle.Sleepsciencemakesitveryclearthatsleepisnotatradablecommodity.

2.2.1WhatisHappeningintheBrainDuringSleepThereareavarietyofwaysoflookingatwhatishappeninginthesleepingbrain,fromreflectingondreamstousing advanced medical imaging techniques. Currently, the most common research method is known aspolysomnography (see Appendix B for details). This involves sticking removable electrodes to the scalp and


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face and connecting them to a recording device, to measure three different types of electrical activity: 1)brainwaves(electroencephalogramorEEG);2)eyemovements(electroculogramorEOG);and3)muscletone(electromyogramorEMG). Usingpolysomnography,itispossibletoidentifytwoverydifferentkindsofsleep.

NonRapidEyeMovementSleep

Comparedtowakingbrainactivity,nonRapidEyeMovementsleep(nonREMsleep)involvesgradualslowingofthebrainwaves.Theamplitude(height)ofthebrainwavesalsobecomeslargerastheelectricalactivityof

largenumbersofbraincells(neurons)becomessynchronizedsothattheyfireinunison.Heartrateandbreathingtendtobeslowandregular.

PeoplewokenfromnonREMsleepdonotusuallyrecallmuchmentalactivity.However,itisstillpossibleforthebodytomoveinresponsetoinstructionsfromthebrain. Becauseofthesefeatures,nonREMsleepissometimesdescribedasarelativelyinactivebraininamovablebody.

NonREMsleepisusuallydividedinto4stages,basedonthecharacteristicsofthebrainwaves.

Stages1and2representlightersleep(itisnotverydifficulttowakesomeoneup).ItisusualtoentersleepthroughStage1andthenStage2nonREM.

Stages 3 and 4 represent deeper sleep (it can be very hard to wake someone up). Stages 3 and 4 arecharacterizedbyhighamplitudeslowbrainwaves,andaretogetheroftendescribedasslowwavesleep(ordeepsleep).

Slowwavesleephasanumberofimportantproperties.Pressureforslowwavesleepbuildsupacrosswakinganddischargesacrosssleep.Inotherwords:

thelongeryouareawake,themoreslowwavesleepyouwillhaveinyournextsleepperiod;and acrossasleepperiod,theproportionoftimespentinslowwavesleepdecreases.

Thisrisingandfallingofpressureforslowwavesleepissometimescalledthesleephomeostaticprocess,andit

isacomponent

in

most

of

the

bio

mathematical

models

that

are

used

to

predict

crewmember

fatigue

levels

(seeChapterFour).

Eveninslowwavesleep,thebrainisstillabout80%activatedandcapableofactivecognitiveprocessing.Thereisgrowingevidencethatslowwavesleep isessential for theconsolidationofsometypesofmemory,and isthereforenecessaryforlearning.


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RapidEyeMovementSleep

DuringRapidEyeMovementsleep(REMsleep),brainactivitymeasuredbypolysomnography lookssimilartobrainactivityduringwaking.However inREMsleep,fromtimetotimetheeyesmovearoundundertheclosedeyelidsthesocalledrapideyemovementsandthisisoftenaccompaniedbymuscletwitchesandirregularheartrateandbreathing.

PeoplewokenfromREMsleepcantypicallyrecallvividdreaming.Atthesametime,thebodycannotmoveinresponsetosignalsfromthebrainsodreamscannotbeactedout.(Thesignalseffectivelygetblockedinthe

brainstemandcannotgetthroughtothespinalcord.)Peoplesometimesexperiencebriefparalysiswhentheywakeupoutofadream,whenreversalofthisREMblockisslightlydelayed.Becauseofthesefeatures,REMsleepissometimesdescribedasahighlyactivatedbraininaparalysedbody.

Dreams have always been a source of fascination, but are difficult to study using quantitative scientificmethods.Theyhavebeeninterpretedaseverythingfromspiritualvisitationstofulfillmentofinstinctualdrives,tobeingameaninglessbyproductofactivityinvariouspartsofthebrainduringREMsleep.Thecurrentneurocognitiveviewofdreamingarguesthatitresultsfrombriefmomentsofconsciousnesswhenwebecomeawareofalltheprocessingthatourbrainsnormallydooffline,i.e.whentheyarenotbusydealingwithinformation

OperationalNote:MitigationStrategiesforSleepInertia

Operationally, slowwave sleep may be important because the brain can havedifficultytransitioningoutofitwhensomeoneiswokenupsuddenly.Thisisknown

assleep

inertia

feelings

of

grogginess

and

disorientation,

with

impaired

short

term

memory and decisionmaking. Sleep inertia can occur coming out of lighter sleep,but it tends tobe longerandmoredisorientingwhensomeone iswokenabruptlyoutofslowwavesleep.

Thisissometimesusedasanargumentagainsttheuseofflightdecknappingorinflight sleep. It would not be desirable to have a crewmember who is woken upbecause of an emergency, but who is impaired by sleep inertia. This argument isbasedontheeffectsofsleepinertiaseeninlaboratorystudies.

However,studiesofnappingon the flight deck andofsleep in onboardcrew restfacilitiesshowthatsleep inflightcontainsvery littleslowwavesleep. (It is lighter

and more fragmented than sleep on the ground). This means that sleep inertia ismuch less likely to occur waking up from sleep in flight than would be predictedfromlaboratorysleepstudies.Theriskofsleepinertiacanalsobereducedbyhavingaprotocolforreturningtoactivedutythatallowstimeforsleepinertiatowearoff.

Overall,thedemonstratedbenefitsofcontrollednappingandinflightsleepgreatlyoutweigh the potential risks associated with sleep inertia. To reduce the risk ofsleep inertia after flight deck napping, the recommendation is to limit the timeavailableforthenapto40minutes.Giventhetimetakentofallasleep,a40minuteopportunity is too short for most people to enter slowwave sleep. Refer toAppendix C for suggested Flight Operations Manual procedures for controllednapping.


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cominginfromtheenvironmentthroughthesenses,andarenotbeingdirectedbyourconsciouscontrol.Thisofflineprocessingincludesreactivatingmemoriesandemotionsfrompreviousexperiences,and integratingthem with experiences from the latest period of waking. Dreams in this view are a glimpse into your brainreshapingitselfsothatyoucanwakeupinthemorningstillyourself,butaslightlyrevisedversionasaresultofyourexperiencesyesterday,andreadytostartinteractingwiththeworldagain.

People vary greatly in their ability to recall dreams, and we generally only recall them when we wake

spontaneouslyout of REM sleep (and then only fleetingly unless we write them down or talk about them).Nevertheless,mostadultsnormallyspendaboutaquarteroftheirsleeptimeinREMsleep.

NonREM/REMCycles

Acrossanormalnightofsleep,nonREMsleepandREMsleepalternateinacyclethatlastsroughly90minutes(butisveryvariableinlength,dependingonanumberoffactors).Figure2.1isadiagramdescribingthenonREM/REMcycleacrossthenight inahealthyyoungadult.Realsleep isnotas tidyas this it includesmorearousals(transitionstolightersleep)andbriefawakenings. Sleepstagesareindicatedontheverticalaxisandtimeisrepresentedacrosshorizontalaxis3.

Figure2.1:DiagramofthenonREM/REMcycleacrossthenightinayoungadult

SleepisenteredthroughStage1nonREMandthenprogressesdeeperanddeeperintononREM.About8090minutesintosleep,thereisashiftoutofslowwavesleep(nonREMstages3and4).Thisisoftenmarkedby

bodymovements,

as

the

sleeper

transitions

briefly

through

Stage

2non

REM

and

into

the

first

REM

period

of

thenight. (REMperiodsare indicatedasshadedboxes inFigure2.1).Aftera fairlyshortperiodofREM, thesleeperprogressesbackdownagainthroughlighternonREMsleepandintoslowwavesleep,andsothecyclerepeats.

3GanderPH(2003)Sleepinthe24HourSociety.Wellington,NewZealand:OpenMindPublishing.ISBN0909009597


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The amount of slowwave sleep in each nonREM/REM cycle decreases across the night, and there may benone at all in the later cycles. In contrast, the amount of REM sleep in each nonREM/REM cycle increasesacrossthenight.ThesleeperdepictedinFigure2.1wakesupdirectlyoutofthefinalREMperiodofthenight,andsowouldprobablyrecalldreaming.

Interestingly, slowwave sleep always predominates at the beginning of a sleep period, regardless of whensleep occurs in the day/night cycle or in the circadian body clock cycle. There seems to be a priority to

dischargethehomeostaticsleep

pressurefirst.Incontrast,thetimefromsleeponsettothefirstboutofREM

(theREM latency)andthedurationofeachREMboutvariesmarkedlyacrossthecircadianbodyclockcycle.ThecircadiandriveforREMsleepisstrongestafewhoursbeforenormalwakeuptime.Thesetwoprocessesthe homeostatic sleep process and the circadian body clock are the main components in most of the biomathematicalmodelsthatareusedtopredictcrewmemberfatiguelevels(seeChapterFour).

2.2.2TheIssueofSleepQualitySleepquality(itsrestorativevalue)dependsongoingthroughunbrokennonREM/REMcycles(whichsuggeststhat both types of sleep are necessary and one is not more important than the other). The more the nonREM/REMcycle is fragmented by wakingup, or by arousals that move the brain to a lighter stage of sleepwithoutactuallywakingup,thelessrestorativevaluesleephasintermsofhowyoufeelandfunctionthenextday.

OperationalNote:MitigationStrategiesforSleepLoss

RestorationofanormalnonREM/REMcycle isonemeasureof recovery from the

effects of sleep loss. Lost sleep is not recovered hourforhour, although recoverysleepmaybeslightlylongerthanusual.

On the first recoverynight, there ismoreslowwavesleep thanusual. Indeed,therecanbesomuchslowwavesleepthatthereisnotenoughtimetomakeupREMsleep.

Onthesecondrecoverynight,thereisoftenmoreREMsleepthanusual. Bythethirdrecoverynight,thenonREM/REMcycleisusuallybacktonormal.

Operationally,thismeansthatschedulesneedtoperiodicallyincludeanopportunityforatleasttwoconsecutivenightsofunrestrictedsleep,toenablecrewmemberstorecoverfromtheeffectsofsleeploss.

This does not equate to 48 hours off. For example, 48 hours off duty starting at02:00wouldonlygivemostpeopletheopportunityforonefullnightofunrestrictedsleep.Ontheotherhand,40hoursoffstartingat21:00wouldgivemostpeopletheopportunityfortwofullnightsofunrestrictedsleep.

Additional nights may be needed for recovery if a crewmembers circadian bodyclockisnotalreadyadaptedtothelocaltimezone(seeSection2.3).


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QualityofInFlightSleep

Asmentionedabove,polysomnographystudiesshowthatcrewmemberssleepinonboardcrewrestfacilitiesislighterandmorefragmentedthansleepontheground4.Sleepduringflightdecknapsisalsolighterandmorefragmented thanwouldbepredicted from laboratorystudies5.Nevertheless, there isgoodevidence that inflightsleepimprovessubsequentalertnessandreactionspeedandisavaluablemitigationstrategyinanFRMS.

Interestingly, studies of sleep in hypobaric chambers at pressures equivalent to cabin pressure at cruisingaltitudeindicatethatthefragmentedqualityofinflightsleepisnotduetoaltitude6.Severalstudieshaveaskedcrewmemberswhatdisturbs theirsleeponboard.The factorsmostcommonly identifiedare random noise,thoughts,notfeelingtired,turbulence,ambientaircraftnoise,inadequatebedding,lowhumidity,andgoingtothetoilet.

SleepQualityandAging

Acrossadulthood,theproportionofsleeptimespentinslowwavesleepdeclines,particularlyamongmen.Inaddition, sleep becomes more fragmented. For example, one study with 2,685 participants aged 3792 yrs

4Signal,T.L.,Gale,J.,andGander,P.H.(2005)SleepMeasurementinFlightCrew:ComparingActigraphicandSubjectiveEstimatesof

SleepwithPolysomnography.AviationSpaceandEnvironmentalMedicine76(11):105810635Rosekind,M.R.,Graeber,R.C.,Dinges,D.F.,etal.,(1994)CrewFactorsinFlightOperationsIX:Effectsofplannedcockpitrestoncrewperformanceandalertnessinlonghauloperations.NASATechnicalMemorandum108839,MoffettField:NASAAmesResearchCenter.6Mumm,J.M.,Signal,T.L.,Rock,P.B.,Jones,S.P.,OKeeffe,K.M.,Weaver,M.R.,Zhu,S.,Gander,P.H.,Belenky,G.(2009)Sleepat

simulated2438m:effectsonoxygenation,sleepquality,andpostsleepperformance.Aviation,Space,andEnvironmentalMedicine80(8):691697.

OperationalNote:MitigationStrategiestoMinimizeSleepInterruptions

Because uninterrupted nonREM/REM cycles are the key to good quality sleep,

operatorsshould

develop

procedures

that

minimize

interruptions

to

crewmembers

sleep.

Rest periods should include defined blocks of time (sleep opportunities) duringwhich crewmembers are not contacted except in emergencies. These protectedsleep opportunities need to be known to flight crews and all other relevantpersonnel.Forexample,calls fromcrewschedulingshouldnotoccurduringa restperiodastheycanbeextremelydisruptive.

Operatorsshouldalsodevelopprocedurestoprotectcrewmembersleepatlayoverand napping facilities. For example, if a rest period occurs during the day at alayover hotel, the operator could make arrangements with the hotel to restrict

accessto

the

section

of

the

hotel

where

crewmembers

are

trying

to

sleep

(such

as

nochildren,crewmembersonly)andinstructtheirstafftohonorthenecessaryquietperiods(forexample,nomaintenanceworkorroutinecleaning).


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foundthattheaveragenumberofarousals(transitionstolightersleepandawakenings)rosefrom16perhourofsleepfor3054yearoldsto20perhourofsleepfor6170yearolds7.

Theseagerelatedtrendsareseeninthesleepofflightcrewmembers,bothonthegroundandintheair2,8.AstudyofinflightsleepondeliveryflightsofB777aircraft(fromSeattletoSingaporeorKualaLumpur)foundthatagewasthefactorthatmostconsistentlypredictedthequalityanddurationofbunksleep.Olderpilotstooklongertofallasleep,obtainedlesssleepoverall,andhadmorefragmentedsleep.

It is not yet clear whether these agerelated changes in sleep reduce its effectiveness for restoring wakingfunction.Laboratorystudiesthatexperimentallyfragmentsleeparetypicallyconductedwithyoungadults.Ontheflightdeck,experience(bothintermsofflyingskillsandknowinghowtomanagesleepontrips)couldhelpreducepotentialfatigueriskassociatedwithagerelatedchangesinsleep.

SleepDisorders

Thequalityofsleepcanalsobedisruptedbyawidevarietyofsleepdisorders,whichmake it impossible toobtain restorative sleep, even when people spend enough time trying to sleep. Sleep disorders pose aparticularriskforflightcrewmembersbecause,inaddition,theyoftenhaverestrictedtimeavailableforsleep.It isrecommended thatFRMStraining (ChapterSix)should includebasic informationonsleepdisordersandtheirtreatment,wheretoseekhelpifneeded,andanyrequirementsrelatingtofitnesstofly.

2.2.3ConsequencesofNotGettingEnoughSleepEvenforpeoplewhohavegoodqualitysleep,theamountofsleeptheyobtainisveryimportantforrestoringtheirwakingfunction.Anincreasingnumberoflaboratorystudiesarelookingattheeffectsoftrimmingsleepatnightbyanhourortwo(knownassleeprestriction).ThereareseveralkeyfindingsfromthesestudiesthatareimportantforFRMS.

1. Theeffectsofrestrictingsleepnightafternightaccumulate,sothatpeoplebecomeprogressivelylessalertand less functional day after day. This is sometimes described as accumulating a sleep debt. This is acommon occurrence for crewmembers (see below), for example when minimum rest periods are

scheduledforseveraldaysinarow.

2. The shorter the time allowed for sleep each night, the faster alertness and performance decline. Forexample,onelaboratorystudyfoundthatspending7hoursinbedfor7consecutivenightswasnotenoughto prevent a progressive slowing down in reaction time9. The decline was more rapid for a group ofparticipantswhospentonly5hoursinbedeachnight,andevenmorerapidforagroupwhospentonly3hoursinbedeachnight.Thisisdescribedasadosedependenteffectofsleeprestriction.

3. The pressure for sleep increases progressively across successive days of sleep restriction. Eventually, itbecomesoverwhelmingandpeoplebeginfallingasleepuncontrollablyforbriefperiods,knownasmicrosleeps. During a microsleep, the brain disengages from the environment (it stops processing visualinformation and sounds). In the laboratory, this can result in missing a stimulus in a performance test.Drivingamotorvehicle,itcanresultinfailingtotakeacorner.Similareventshavebeenrecordedontheflightdeckduringdescentintomajorairports5.

7Redline,S.,Kirchner,H.L.,Quan,S.F.,Gottlieb,D.J.,Kapur,V.,Newman,A.(2004).Theeffectsofage,sex,ethnicity,andsleep

disorderedbreathingonsleeparchitecture.ArchivesofInternalMedicine164:406418.8Signal,T.L.,Gander,P.H.,vandenBerg,M.(2004)Sleepinflightduringlongrestopportunities.InternalMedicineJournal34(3):A38.

9Belenky,G.,Wesensten,N.J.,Thorne,D.R.,etal.(2003).Patternsofperformancedegradationandrestorationduringsleeprestrictionand

subsequentrecovery:asleepdoseresponsestudy.JournalofSleepResearch12:112.


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4. Fullrecoveryofwakingfunctionaftersleeprestrictioncantakelongerthantwonightsofrecoverysleep(i.e., longerthan ittakesthenonREM/REMcycletorecover). Indeed,chronicsleeprestrictionmayhaveeffectsonthebrainthatcanaffectalertnessandperformancedaystoweekslater10.

5. Forthefirstfewdaysofseveresleeprestriction(forexample,3hoursinbed),peopleareawarethattheyare getting progressively sleepier. However, after several days they no longer notice any difference inthemselves,evenalthoughtheiralertnessandperformancecontinuestodecline.Inotherwords,assleep

restrictioncontinues,peoplebecomeincreasinglyunreliableatassessingtheirownfunctionalstatus.Thisfindingraisesaquestionaboutthereliabilityofsubjectiveratingsoffatigueandsleepinessasmeasuresofacrewmembersleveloffatiguerelatedimpairment(seeAppendixB).

6. At least in the laboratory,somepeoplearemoreresilienttotheeffectsofsleeprestriction thanothers.Currently,thereisalotofresearcheffortaimedattryingtounderstandwhythisis,butitisstilltooearlyforthistobeappliedinanFRMS(forexample,byrecommendingdifferentpersonalmitigationstrategiesforpeoplewhoaremoreorlessaffectedbysleeprestriction).

Ingeneral,morecomplexmentaltaskssuchasdecisionmakingandcommunicationseemtobemoreseverelyaffectedbysleeplossthansimplertasks.Brainimagingstudiesalsosuggestthatthebrainregionsinvolvedin

morecomplex

mental

tasks

are

the

most

affected

by

sleep

deprivation

and

have

the

greatest

need

for

sleep

to

recovertheirnormalfunction.

Laboratory sleep restriction studies are currently the main source of information on the effects of sleeprestriction.However, they have some obvious limitations. The consequences of reduced alertnessandpoortask performance are quite different in the laboratory than for crewmembers on duty. Laboratory studiesusuallylookattheeffectsofrestrictingsleepatnightandparticipantssleepinadark,quietbedroom.Thismaymeanthatcurrentunderstandingisbasedonabestcasescenario.Moreresearchisneededontheeffectsofrestrictingsleepduringtheday,andonthecombinationofrestrictedsleepandpoorqualitysleep.Laboratorystudiesalsofocusontheperformanceofindividuals,notpeopleworkingtogetherasacrew.

One simulation study with 67 experienced B747400 crews has demonstrated that sleep loss increased thetotalnumberoferrorsmadeby thecrew11.Thestudydesignwassetupso that thepilot incommand wasalways the pilot flying. Paradoxically, greater sleep loss among first officers improved the rate of errordetection.Ontheotherhand,greatersleeplossamongpilotsincommandledtoahigherlikelihoodoffailureto resolve errors that had been detected. Greater sleep loss was also associated with changes in decisionmaking,includingatendencytochooselowerriskoptions,whichwouldhelpmitigatethepotentialfatiguerisk.Simulatorstudies like this areexpensiveand logisticallycomplex toconductproperly,but theyprovidevitalinsightsonthelinksbetweencrewmembersleepandoperationalfatiguerisk.

SleepRestrictioninFlightOperations

Theideaofsleeprestrictionimpliesthatthereisanoptimumamountofsleepthatpeopleneedtoobtaineachnight.Theconceptofindividualsleepneedisanareaofactivedebateinsleepresearch.Onewaytomeasure

sleeprestrictionthatavoidsthisproblemistolookathowmuchsleepcrewmembersobtainwhentheyareathomebetweentrips,comparedtohowmuchsleeptheyobtainduringtrips.

10Rupp,T.L.,Wesensten,N.J,Bliese,P.D.etal.(2009).Bankingsleep:realizationofbenefitsduringsubsequentsleeprestrictionand

recovery.Sleep32(3):31132111 Thomas, M.J.W., Petrilli, R.M., Lamond, N.A., et al. (2006). Australian Long Haul Fatigue Study. In: Enhancing SafetyWorldwide:

Proceedingsofthe59thAnnualInternationalAirSafetySeminar.Alexandria,USA,FlightSafetyFoundation.


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Table2.1summarizesdataonsleeprestrictionacrossdifferent flightoperationsthatweremonitoredbytheNASAFatiguePrograminthe1980s12.Inthesestudies,crewmemberscompletedsleepanddutydiariesbefore,during,andafterascheduledcommercialtrip.Foreachcrewmember,hisaveragesleepdurationper24hoursathomebeforethetripwascomparedwithhisaveragesleepdurationper24hoursonthestudytrip.Duringnightcargoandlonghaultrips,crewmembersoftenhadsplitsleep(sleptmorethanoncein24hours).

Scheduling has undoubtedly changed since these studies, so the data in Table 2.1 are likely to be

unrepresentativeofthecurrentsituation inmanycases.However,they indicatethatsleeprestriction isverycommonacrossdifferenttypesofflightoperations.

Table2.1:Sleeprestrictionduringcommercialflightoperations

ShortHaul NightCargo LongHaul

crewmembersaveragingatleast1hourofsleeprestrictionpertripday

67% 54% 43%

crewmembersaveragingatleast2

hoursofsleeprestrictionpertripday

30% 29% 21%

lengthoftrip 34days 8days 49days

timezonescrossedperday 01 01 08

numberofcrewmembersstudied 44 34 28Note:thenightcargotripsincludeda12nightbreakinthesequenceofnightshifts.Splittinglonghaultripsinto24hoursdaysisratherarbitrary,becausetheaveragedutydaylasted10.2hoursandtheaveragelayoverlasted24.3hours.

Agrowingamountofevidence,frombothlaboratorystudiesandfromepidemiologicalstudiesthattrackthe

sleepand

health

of

large

numbers

of

people

across

time,

indicates

that

chronic

short

sleep

may

have

negative

effectsonhealth inthe longterm.Thisresearchsuggeststhatshortsleepersareatgreaterriskofbecomingobeseanddevelopingtype2diabetesandcardiovasculardisease.Thereisstilldebateaboutwhetherhabitualshortsleepactuallycontributes to thesehealthproblems,or isjustassociatedwith them. Inaddition, flightcrewmembersasagroupareexceptionallyhealthycomparedtothegeneralpopulation.Whatisclearisthatgoodhealthdependsnotonlyongooddietandregularexercise,butalsoongettingenoughsleeponaregularbasis. Sleepisdefinitelynotatradablecommodity.

12Gander,P.H.,Rosekind,M.R.,andGregory,K.B.(1998)FlightcrewfatigueVI:anintegratedoverview.Aviation,Space,andEnvironmental

Medicine69:B49B60


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2.3IntroductiontoCircadianRhythmsSleepingatnight isnotjustasocialconvention. It isprogrammed intothebrainbythecircadianbodyclock,which is an ancient adaptation to life on our 24hour rotating planet. Even very ancient types of livingorganisms have something equivalent, which means that circadian biological clocks have been around forseveralbillionyears.

Afeatureofcircadianclocksisthattheyarelightsensitive.Thehumancircadianclockmonitorslightintensitythroughaspecialnetworkofcellsintheretinaoftheeye(thisspeciallightinputpathwaytothecircadianclockisnotinvolvedinvision).Theclockitselfresidesinafairlysmallclusterofcells(neurons)deeperinthebrain(inthe suprachiasmatic nuclei (SCN) of the hypothalamus). The cells that make up the clock are intrinsicallyrhythmic, generating electrical signals faster during the day than during the night. However, they have atendencytoproduceanoverallcyclethatisabitslowformostpeoplethebiologicaldaygeneratedbythe

circadianbodyclockisslightlylongerthan24hours.Thesensitivityofthecircadianbodyclocktolightenablesit to stay instepwith the day/nightcycle. However, thatsamesensitivity to lightalso createsproblems forcrewmemberswhohavetosleepoutofstepwiththeday/nightcycle (forexampleondomesticnightcargooperations),orwhohavetoflyacrosstimezonesandexperiencesuddenshiftsintheday/nightcycle.

2.3.1ExamplesofCircadianRhythmIt is not possible to directly measure the electrical activity of the circadian body clock in human beings.However, almost every aspect of human functioning (physical or mental) undergoes daily cycles that are

OperationalNote:MitigationStrategiesforManagingSleepDebt

Sleeprestrictioniscommonacrossdifferenttypesofflightoperations.Becausethe

effects

of

sleep

restriction

are

cumulative,

schedules

must

be

designed

to

allow

periodic opportunities for recovery. Recovery opportunities need to occur morefrequently when daily sleep restriction is greater, because of the more rapidaccumulationoffatigue.

The usual recommendation for a recovery opportunity is for a minimum of twoconsecutive nights of unrestricted sleep. Some recent laboratory studies of sleeprestrictionsuggestthat thismaynotbeenough tobringcrewmembersbackup totheiroptimal levelof functioning.There isevidence that thesleeprestrictedbraincanstabilizeatalowerleveloffunctioningforlongperiodsoftime(daystoweeks).

Especiallyinirregularoperations,proceduresthatallowacrewmembertocontinue

sleeping

until

needed

can

reduce

the

rate

of

accumulation

of

sleep

debt.

For

example, ifanaircraftwithananticipated repair timeof0730willnotactuallybeready until 11:30, then a reliable procedure that allows the crew member tocontinuesleepingwouldbebeneficial.Oneairlinehasasystemwheretheoperatorcontacts the layoverhotel toupdate the report time byslipping amessage underthecrewmembersdoor.Thehotelprovidesawakeupcallonehourbeforepickuptime.


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influencedbythecircadianbodyclock. Measuringovertrhythmsinphysiologyandbehaviourislikewatchingthehandsofan(analogue)wristwatch.Thehandsmovearoundthewatchfacebecausetheyaredrivenbythetimekeeping mechanism inside the watch, but they are not part of the timekeeping mechanism itself.Similarly,most circadian rhythms that canbemeasured,such as rhythms in core body temperatureor selfrated fatigue, are driven by the circadian body clock, but they are not part of the biological timekeepingmechanism.

Figure2.2showsanexampleofcircadianrhythmsincorebodytemperatureandselfratedfatigueofa46yearoldshorthaulcrewmembermonitoredbefore,during,andaftera3daypatternofflyingontheeastcoastoftheUSA(stayinginthesametimezone)13. Thecrewmemberhadhiscoretemperaturemonitoredcontinuouslyandkeptasleepanddutydiary,inwhichhenotedhissleeptimesandratedthequalityofhissleep,aswellasratinghisfatigueevery2hourswhilehewasawake(onascalefrom0=mostalertto100=mostdrowsy).

Corebodytemperaturetypicallyfluctuatesbyabout1 Cacrossthe24hourday.Notethatthecrewmember'scoretemperaturestartstoriseeachmorningbeforehewakesup. Ineffect,hisbody isbeginningtoprepareaheadoftimeforthegreaterenergydemandsofbeingmorephysicallyactive.(Ifbodytemperatureonlybegantoriseafterhestartedtobemorephysicallyactive,itwouldbealothardertogetupinthemorning).

Lookingat

his

self

rated

fatigue,

this

crewmember

did

not

feel

at

his

best

first

thing

in

the

morning.

He

tended

tofeelleastfatiguedabout24hoursafterhewokeup,afterwhichhisfatigueclimbedsteadilyacrosstheday.Thedashedlineacrossthesleepperiodindicatesthathewasnotaskedtowakeupevery2hourstoratehisfatigueacrossthistime.

Figure2.2:Circadianrhythmsofashorthaulpilot

13Gander,P.H.,Graeber,R.C.,Foushee,H.C.,Lauber,J.K.,Connell,L.J.(1994).CrewFactorsinFlightOperationsII:Psychophysiological

ResponsestoShortHaulAirTransportOperations.NASATechnicalMemorandum#108856.MoffettField:NASAAmesResearchCenter.


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Corebodytemperatureisoftenuseasamarkerrhythmtotrackthecycleofthecircadianbodyclockbecauseitisrelativelystableandeasytomonitor.However,nomeasurablerhythm isaperfectmarkerofthecircadianbodyclockcycle.Forexample,changesinthelevelofphysicalactivityalsocausechangesincoretemperature,whichexplainsthesmallpeaksanddipsintemperatureinFigure2.2.

Thedailyminimumincorebodytemperaturecorrespondstothetimeinthecircadianbodyclockcyclewhenpeoplegenerallyfeelmostsleepyandare leastabletoperformmentalandphysicaltasks.This issometimes

describedastheWindowof

Circadian

Low

(WOCL).

2.3.2TheCircadianBodyClockandSleepAsmentionedinSection2.2,thecircadianbodyclockinfluencessleepinanumberofways.(Ithasconnectionstocentersinthebrainthatpromotewakefulnessandtoopposingcentersthatpromotesleep,aswellastothesystemthatcontrolsREMsleep.) Figure2.3isadiagramthatsummarizestheeffectsofthecircadianclockonsleep.Itisbasedondatacollectedfrom18nightcargopilotsontheirdaysoff,i.e.,whentheyweresleepingatnight14.LikethecrewmemberinFigure2.2,theyalsohadtheircoretemperaturemonitoredcontinuously,andkeptsleepanddutydiaries.

Thecore

temperature

rhythm

issummarized

as

asimple

(continuous)

curve.

The

daily

time

of

the

minimum

in

temperature(shownbytheblackdot)istheaverageforallcrewmembersandisusedasareferencepointfordescribingtheotherrhythms.Notethatchangesintemperaturearenotthecauseoftheotherrhythms.Thecorebodytemperaturerhythmisbeingreadlikethehandsofananaloguewristwatch,asawayoffollowingtheunderlyingcycleofthecircadianbodyclock.

Figure2.3:Summaryoftheinfluencesofthecircadianbodyclockonsleepatnight

14Gander,P.H.,Rosekind,M.R.,andGregory,K.B.(1998)FlightcrewfatigueVI:anintegratedoverview.Aviation,

Space,andEnvironmentalMedicine69:B49B60


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Figure2.3summarizesthefollowingfeaturesofsleepatnight(whencrewmembersarefullyadaptedtothelocaltimezone).

Sleepnormallybeginsabout5hoursbeforetheminimumincorebodytemperature. Wakeupnormallyoccursabout3hoursaftertheminimumincorebodytemperature. REMsleep isentered fastest,andREMperiodsare longestandmost intense,justafter theminimum in

core body temperature. This is sometimes described as the peak of the circadian rhythm in REMpropensity(thedashedcurveinFigure2.3).

Avarietyoflaboratoryprotocolshavedemonstratedpeopleareextremelyunlikelytofallasleep68hoursbeforetheminimumincorebodytemperature.Thishasbecomeknownastheeveningwakemaintenancezone.

Laboratorystudiesalsoshow thatasbody temperaturebegins to rise,there isan increasingpressuretowakeup.Thispeaksabout6hoursafterthecircadiantemperatureminimum.Thisissometimesreferredtoas an internal alarm clock, because it is very hard to fall asleep or stay asleep during this part of thecircadianbodyclockcycle.

Theinteractionbetweenthehomeostaticpressureforsleepandthecircadianvariationinsleepinessdrivenby

thebodyclock resultsintwotimes

of

peak

sleepiness

in

24

hours;

apeakintheearlyhoursofthemorningthesocalledWindowofCircadianLow(WOCL),whichoccursaround35amformostpeople;and

a peak in the early afternoon sometimes called the afternoon nap window (around 35 pm for mostpeople). Restricted sleep at night, or disturbed sleep makes it harder to stay awake during the nextafternoonnapwindow.

The precise timing of the two peaks in sleepiness is different in people who are morning types (whosecircadian rhythms and preferred sleep times are earlier than average) and evening types (whose circadianrhythms and preferred sleep times are later than average). Across the teenage years, most people become

more eveningtype. Across adulthood, most people become more morningtype. This progressive changetowardsbecomingmoremorningtypehasbeendocumentedinflightcrewmembersacrosstheagerange2060years.

Thecombinedeffectsofthehomoeostaticpressureforsleepandthecircadianbiologicalclockcanbethoughtofasdefiningwindowswhensleepispromoted(theearlymorningandafternoontimesofpeaksleepiness)andwindowswhensleepisopposed(thetimeoftheinternalalarmclockinthelatemorning,andtheeveningwakemaintenancezone).


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2.3.3SensitivityoftheCircadianBodyClocktoLightAtthebeginningofthisChapter,therewasabriefdescriptionofhowthecircadianbodyclockisabletotracklightintensityintheenvironment.Thisenablesittostayinstepwiththeday/nightcycle,evenalthoughithasatendencytogenerateabiologicaldaythatisslightlylongerthan24hours.

Theeffect

of

light

on

the

circadian

body

clock

changes

according

to

when

in

the

clock

cycle

the

light

exposure

occurs.Foracrewmemberadaptedtolocaltimeandsleepingatnight:

light exposure in the morning (after the temperature minimum) causes the circadian clock to speed uptemporarily,resultinginaphaseadvance(equivalenttocrossingtimezonesinaneastwarddirection);

lightexposureinthemiddleofthedayhasverylittleeffect;and lightexposureintheevening(beforethetemperatureminimum)causesthecircadianclocktoslowdown

temporarily,resultinginaphasedelay(equivalenttocrossingtimezonesinawestwarddirection).

OperationalNote:TheCircadianBodyClock,Sleep,andFRMS

The daily minimum in core body temperature corresponds to the time in thecircadian body clock cycle when people feel most sleepy and are least able to

perform

mental

and

physical

tasks.

This

is

sometimes

called

the

Window

of

CircadianLow(WOCL)anditisatimeofhighriskforfatiguerelatederror.InFRMSincidentinvestigations,itisimportanttoestimatethetimethaterrorsoccurrelativetotheexpectedtimeoftheWOCL.

TheWOCLcanoccurinflightduringdomesticnightoperationsandduringlonghauland ULR operations when the duty/rest cycle is out of step with crewmemberscircadianbodyclockcycles.

Theeveningwakemaintenancezoneoccursinthefewhoursbeforeusualbedtime.Thismakesitverydifficulttofallasleepearlythenightbeforeanearlydutyreporttime.Thishasbeenidentifiedacauseofrestrictedsleepandincreasedfatiguerisk

inshorthauloperationsthatrequireearlystarts.

The increasing drive for wake that accompanies the increase in core bodytemperatureinthemorningmakesitdifficulttofallasleeporstayasleeplaterinthemorningandintheearlyafternoon.Thishasbeenidentifiedasacauseofrestrictedsleep and increased fatigue risk in night cargo operations, which requirecrewmemberstodelaytheirmainsleepperioduntilthemorning.

The internal alarm clock and the evening wake maintenance zone can alsointerfere with the inflight sleep and layover sleep of long haul and ULRcrewmemberswhentheduty/restcycleisoutofstepwithcrewmemberscircadian

bodyclockcycles.


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Bright lightcausesbiggershifts in thecircadianbodyclockcycle thandim light,and theclock isparticularlysensitivetobluelight.Intheory,thismeansthatjusttherightamountoflightexposureatthesametimeeverymorningwouldspeedupa24.5hourcircadianclockcyclejustenough tosynchronize it toexactly24hours. Inpractise,staying instepwiththeday/nightcycleismorecomplexthanthis. Inmodern industrialisedsocieties,peoplehaveveryhaphazardexposurestolight,particularlybrightoutdoorlight.Inaddition,thecircadianbodyclockissensitivetoothertimecuesfromtheenvironment,notablysocialcues,andcanalsobemovedbackwardsorforwardsin

itscyclebyboutsofphysicalactivity.

Theabilityofthecircadianclocktolockontothe24hourday/nightcycleisakeyfeatureofitsusefulnessformostspecies,enablingthemtobediurnalornocturnalasneededtoenhancetheirsurvival.However, ithasbecome a disadvantage in the 24/7 society because it causes the human circadian body clock to resistadaptationtoanypatternotherthansleepatnight.

2.3.4ShiftWorkFrom the perspective of human physiology, shift work can be defined as any duty pattern that requires acrewmembertobeawakeduringthetimeinthecircadianbodyclockcyclethattheywouldnormallybeasleep.

The furthersleep isdisplaced from theoptimumpartof thecircadianbodyclockcycle, themoredifficult itbecomesforcrewmemberstogetadequatesleep(i.e.,themorelikelytheyaretoexperiencesleeprestriction).Forexample,crewmembersflyingdomesticnightcargooperationsaretypicallyondutythroughmostoftheoptimum time forsleep in thecircadianbodyclockcycle. Thishappensbecause thecircadianbodyclock islocked on to the day/night cycle, and does not flip its orientation to promote sleep during the day whencrewmembersareflyingatnight.

Figure 2.4 summarises what happened to the circadian biological clock and sleep when the night cargocrewmembersinFigure2.3wereflyingatnightandtryingtosleepinthemorning.(Recallthattheyhadtheircoretemperaturemonitoredcontinuouslyacross8daytrippatterns,andkeptsleepanddutydairies.)

Thecoretemperaturerhythmissummarizedasasimple(continuous)curve.LookingbackatFigure2.3,whenthesecrewmemberswereoffdutyandsleepingatnight,theaveragetimeofthetemperatureminimumwas05:20. In Figure 2.4, when they were working through the night, the average time of the temperatureminimumshiftedto08:08(adelayof2hours48minutes).Thisconfirmsthatthecircadianbodyclockdidnotadaptfullytonightduty(whichwouldhaverequiredashiftofabout12hours).


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Figure2.4:Thecircadianbodyclockandsleepafternightduty

Theincompleteadaptationofthecircadianclockforcedcrewmemberstosleepinadifferentpartofthecircadianbodyclockcycleafternightduty.

Athomebeforethetrip(Figure2.3),theywenttosleepabout5hoursbeforethetemperatureminimumandwokeupabout3hoursafterthetemperatureminimum.

Afternightduty(Figure2.4),theywenttosleepclosetothecircadiantemperatureminimumandwokeupabout6hourslater.Theaveragetimeofwakingupaftermorningsleepperiodswas14:13.Thepredictedtimeoftheinternalalarmclock(6hoursafterthetemperatureminimum)was14:08.Crewmemberswerenotaskedwhatwokethemup,buttheyratedthemselvesasnotfeelingwellrestedaftertheserestrictedmorningsleepepisodes.

Another consequence of the incomplete adaptation of the circadian body clock to night duty was thatcrewmemberswereoftenoperatingthelastflightofthenightintheWindowofCircadianLow(WOCL)whentheywouldbeexpectedtobesleepyandhavingtomakeadditionalefforttomaintaintheirperformance.Nofatiguerelated incidents were observed on these flights (all crews were accompanied by a flight deckobserver).However,allflightswereroutine,i.e.,therewerenooperationaleventsthattestedthecapacityofthesecrewmemberstorespondtononroutinesituations.


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2.3.5JetLagFlyingacrosstimezonesexposesthecircadianbodyclocktosuddenshiftsintheday/nightcycle.Becauseofitssensitivitytolightand(toalesserextent)socialtimecues,thecircadianbodyclockwilleventuallyadapttoanewtimezone.Studieswithparticipantsflownaspassengershave identifiedanumberof factorsthataffecttherateofadaptationtoanewtimezone.Thesefactorsincludethefollowing.

Thenumberoftimezonescrossed adaptationgenerallytakeslongerwhenmoretimezonesarecrossed. Thedirectionoftravel adaptationisusuallyfasterafterwestwardtravelthanaftereastwardtravelacross

thesamenumberoftimezones.

Thisprobably

reflects

the

fact

that

most

people

have

acircadian

body

clock

that

has

an

innate

cycle slightly longer than 24 hours, which makes it easier to lengthen the cycle to adapt to awestwardshift(aphasedelay).

Aftereastwardflightsacross6ormoretimezones,thecircadianbodyclockmayadaptbyshiftingintheoppositedirection,forexampleshifting18timezoneswestratherthan6timezoneseast.When this happens some rhythms shift eastward and others westward (known asresynchronizationbypartition)andadaptationcanbeparticularlyslow.

Rhythmsindifferentfunctionscanadaptatdifferentrates,dependingonhowstronglytheyareinfluencedbythecircadianbodyclock.

OperationalNote:MitigationStrategiesforNightDuty

Night duty forces crewmembers to sleep later than normal in their circadian body clockcycle. This means that they have a limited amount of time to sleep before the circadianbody clock wakes them up. Consequently, they need to get to sleep as soon as possible

aftercomingoffduty.

Getting off duty earlier increases the time available for sleep in the morning, before thecircadianbodyclockmakesitdifficultforcrewmemberstostayasleep.

Napping before going on duty is beneficial to help maintain alertness and performancethroughtotheendofthenight

Nappingduringthedutyperiod(forexample,onthegroundwhileaircraftarebeingloadedandunloaded)isbeneficialtohelpmaintainalertnessandperformancethroughtotheendof the night. The napping opportunity should be limited to 4045 minutes, with an

additional1015minutesallowedtoensurethatsleepinertia(ifany)hasdissipated.

Insomeoperations, itmaybepossible toschedulea longersleepopportunityduring thenight, for example during loading and unloading of freight, or during continuous dutyovernightperiods.Providingasleepingroomawayfromtheaircraftandprotectedtimetosleepwouldincreasetheamountofsleepthatcrewmembersareabletoobtain.Onceagain1015minutesallowed,toensurethatsleepinertia(ifany)hasdissipated.


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Thismeansthatduringadaptationtothenewtimezone,rhythmsindifferentbodyfunctionscanbedisturbedfromtheirusualrelationshipstooneanother.

Adaptationisfasterwhenthecircadianbodyclockismoreexposedtothetimecuesthatitneedstolockonto inthenewtimezone.Thisrelatestotheextenttowhichpeopleadoptthepatternofsleep,eatingetc,inthenewtimezoneandtheamountoftimetheyspendoutdoorsinthefirstfewdays.

Beginningatripwithasleepdebtseemstoincreasethedurationandseverityofjetlagsymptoms.

Duringtheperiodofadaptationtothenewtimezone,commonsymptomsincludewantingtoeatandsleepattimesthatareoutofstepwiththelocalroutine,problemswithdigestion,degradedperformanceon mentalandphysicaltasks,andmoodchanges.

Thesituationforlonghaulandultralongrangeflightcrewisdifferenttothatforthepassengerwhoplanstospend longenoughat thedestination toadapt fullyto localtime.Typically, layovers ineachdestination lastonly 12 days, after which crewmembers are asked to operate a return flight or additional flights in thedestination region, followedby thereturn flight(s) to theircityoforigin.Thismeans thatthecircadianbodyclockdoesnothaveenoughtimetoadapttoanyofthedestinationtimezones.Inaddition,thecombinationofa longduty day followedby12day layoversgivesaduty/rest cycle thatdoesnot followa regular24hourpattern,sothecircadianbodyclockcannotlockontotheduty/restcycle.

Relatively few studies have tracked the circadian body clock across commercial longhaul trip patterns andnonehave tracked itacrossULRoperations.Figure 2.5depictsdata fromoneNASAstudyconducted in themid1980sonB747200/300operations (3personcrewsconsistingofapilot incommand , firstofficer,andflightengineer)15.Similartrippatternsarestillbeingflownbysomeoperatorsbutwithanadditionalpilot,nota flightengineer.Participantshad theircorebody temperaturemonitoredcontinuously andkeptsleepanddutydiariesbefore,during,andafterthistrip,whichincluded4transPacificflightsplusoneroundtripwithinAsia (NRTSINNRT). The dots on the graph indicate the time of the temperature minimum (averaged for 6crewmembersperday).

15Gander,P.H.,Gregory,K.B.,Miller,D.L.,Rosekind,M.R.,Connell,L.J.,andGraeber,R.C.(1998)FlightcrewfatigueV:long

haulairtransportoperations.Aviation,Space,andEnvironmentalMedicine69:B37B48


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Figure2.5:StudytrackingthecircadianbodyclockacrossmultipletransPacificflights

Bytheendofthistrippattern,thetemperatureminimumhaddelayedbyabout4.5hours,givinganaveragedriftrateofabout30minutesper24hours (oranaveragecycle lengthofthecircadianbodyclockofabout24.5hours).Thedriftpresumablywastheresultofthefactthatthecircadianbodyclockdidnothaveany24hourtimecuestolockonto,withthenon24hrduty/restcycleandeverylayoverinadifferenttimezone.

One consequence was that the temperature minimum (corresponding to the Window of Circadian Low orWOCL) sometimes occurred in flight, for example on the last flight from NRT to SFO. At these times,crewmembers would be expected to be sleepy and having to make additional effort to maintain theirperformance.Thiswouldbean idealtimetotakean inflightnap (crewmembersdidnothave inflightsleepopportunitiesonthistrip).

Another consequence was that when crewmembers returned home, their circadian body clocks were onaverage4.5hoursdelayedwithrespecttolocaltimeandtookseveraldaystoreadapt.

LayoverSleep

Patterns

on

Long

Haul

and

ULR

Trips

The fact that long haul and ULR crewmembers seldom stay long enough in any destination time zone tobecomeadaptedtolocaltimehaseffectsontheirlayoversleep.Often,crewmemberssplittheirsleep,havingone sleep period on local night and another corresponding to local night in their home time zone, whichoverlapsthepreferredpartofthecircadianbodyclockcycleforsleep(atleastforthefirst2448hoursinanewtimezone).


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Anotherfactoraffecting layoversleep,particularly forunaugmentedcrewswhodonothavetheopportunityfor inflight sleep, is that long haul duty days are often associated with extended periods of waking. Forexample, in a series of long haul trips studied by the NASA Fatigue Program the average period of wakingassociatedwithadutydaywas20.6hours(theaveragelengthofadutyperiodwas9.8hours)13. Acrosstheselongperiodsofwaking,thehomeostaticpressureforsleepbuildssothatcrewmemberstendtosleep,atleastforashorttime,soonafterarrivalatthedestinationlayoverhotel.Forexample,thisisacommonpatternaftereastward night flights across multiple time zones. A short sleep is taken soon after arrival, during the local

afternoon,andthenthemainsleepperiodisthentakenduringlocalnight.

FRMStrainingforlonghaulandULRcrewmembersneedstoincludediscussionoftheeffectsoftransmeridianflightsonthecircadianbodyclockandsleep.Onewaytoreducethecomplexityofthismaterialistodevelopspecificguidanceforsleepandtheuseofpersonalfatiguemitigationstrategiesondifferentroutes.

OperationalNote:EffectsofDifferentTypesofLongHaulTripPatterns

ontheCircadianBodyClock

Relativelyfewstudieshavetrackedthecircadianbodyclockacrosslonghaultrippatterns,andmanyareover20yearsold.Theavailablestudiessuggestthatdifferenttypesoftrippatternsaffectthecircadianbodyclockindifferentways.

Sequencesofbacktobacktransmeridian flights (separatedby24hour layovers)thatdonot return to the domicile time zone for long periods of time (such as the patternillustratedinFigure2.5)tendtocausethecircadianbodyclocktodriftonitsinnatecycle,whichistypicallyslightlylongerthan24hours.Thisisprobablybecausethesetripscontainnoregular24hourpatterntowhichthecircadianbodyclockcansynchronize.Whentheyarrivebackintheirhometimezone,crewmembersneedadditionaldaystoreadapttolocaltime.

Sequences of outandback transmeridan flights (separated by 24 hour layovers) thatreturn to the home time zone on alternate layovers seem to enable the circadian body

clocktoremainsynchronizedtothehometimezone.Forexample,atrippatternstudiedbytheNASAFatigueProgram involvedthreebacktobackreturn flightsbetweentheUSWest Coast and London (6 flights in total) with 24hour layovers between each flight.Returning to their home time zone on every second layover appeared to keepcrewmembers circadian body clocks (monitored by the core temperature rhythm)synchronizedtoWestCoasttime.Asaresult,crewmembersobtainedrelativelygoodsleepontheWestCoastlayoversanddidnotneedadditionaldaystoreadapttoWestCoasttimeattheendofthetrip.

Thereissomeevidencethatwhencrewmembersstaylongerinthedestinationregion,forexampledoingseveraldaysoflocalflyingwithminimaltimezonechangesbeforeflyingthe

longhaul

trip

home,

their

circadian

body

clocks

begin

to

adapt

to

the

destination

time

zone.Thismay improve layoversleep.Ontheotherhand,whentheyarriveback intheirhometimezone,theyneedadditionaldaystoreadapttolocaltime.

Thescarcityofdataonwhathappenstothecircadianbodyclockacrossdifferentlonghaultrippatterns is one reason most current biomathematical models do not have a validatedapproach for simulating what happens to the circadian clock across sequences of transmeridianflights(seeChapterFour).


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2.4SummaryofEssentialScienceforFRMSDiscoveriesinsleepscienceandcircadianrhythmsprovideastrongscientificbasisforFRMS.Thesciencedoesnotaddresseverydetailedoperationalquestionanditneverwill.Inotherwords,therewillalwaysbeaneedtocombineoperationalexperienceandscientificknowledgetocomeupwithworkablecontrolsandmitigationstomanagefatigueriskinanFRMS.

ThescientificbasisforFRMScanbecontinuouslyimprovedifdatathatareroutinelycollectedaspartofFRMprocesses(ChapterFour)andFRMSAssuranceprocesses(ChapterFive)canbesharedinappropriatewaysinthepublicdomain.


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OperationalNote:KeyFactsAboutSleep

Sleep isvitalforrecoveryfromfatigue.Twoaspectsofsleepare importanttheamountofsleepandthequalityofsleep.

AmountofSleep Sleeprestrictioniscommoninflightoperations.

Not

getting

enough

sleep

leads

to:

feeling

sleepier,

difficulty

staying

alert,

getting

irritable,

slower

reactions,poorercoordination,slowerthinking,gettingfixatedonpartofaproblemand losingthebigpicture(lossofsituationawareness), lesscreativeproblemsolving,andreducedmemoryconsolidation(impairedlearning).

Theeffectsofrestrictedsleepaccumulate: the rateofaccumulationof fatigue is related to the rateof sleep loss (lesssleepperday=more

rapidaccumulationoffatigue); sleep pressure eventually becomes uncontrollable, which results in unintentional sleep

(microsleepsorunintendednaps). Losthoursofsleepdonotneedtoberecoveredhourforhour. Atleasttwoconsecutivenightsofunrestrictedsleeparerequiredtorecoverfromthecumulativeeffects

ofmultiplenightsofrestrictedsleep.Unrestrictedsleepmeansbeingfreetofallasleepwhentiredandwakeupspontaneously,withsleepoccurringattheappropriatetimeinthecycleofthecircadianbody

clock.Insomecases,thisrecoveryperiodcanbebuilt intoschedules(forexamplewithshortdaytimedutyperiods).

Controlled napping can temporarily relieve the symptoms of sleep loss. It is a valuable personalmitigationstrategy,forexamplepriortoanightdutyperiodoronlonghaulflights. ANASAstudyof flightdecknappingshowed improvedalertnessattheendofunaugmented long

haulflights(89hrs)whenflightcrewmembersweregivena40minnapopportunityintheirflightdeckseat.

QualityofSleep Goodqualitysleep involvesregularcyclesthroughtwodifferenttypesofsleepRapidEyeMovement

sleep(REMsleep)andnonREMsleep.AfullnonREM/REMsleepcycletakesroughly90minutes. Sleepthatisfragmentedbymultipleawakenings,orarousalsinto lighterstagesofsleep,breaksupthe

nonREM/REMcycleandislessrestorativethancontinuoussleep. Sleepinonboardcrewrestfacilitiesislighterandmorefragmentedthansleepinhotelsorathome.

Thisdoesnotappeartobeaneffectofaltitude. Both flight decknaps and inflight sleep in crew rest facilities containvery littledeep nonREM sleep

(known as slowwave sleep), so sleep inertia is less likely after inflight sleep than is predicted bylaboratorystudies.

Twomainphysiologicalprocessesinteracttoregulatesleep The homeostatic sleep process is evident in the pressure for slowwave sleep that builds up across

wakinganddischargesacrosssleep.

The circadian body clock regulates the timing of REM sleep and dictates the preference for sleep atnight.

The

interaction

between

the

homeostatic

pressure

for

sleep

and

the

circadian

body

clock

results

in

two

timesofpeaksleepinessin24hours: a peak in the early afternoon (the afternoon nap window) that occurs around 35 pm for most

people;and apeakintheearlyhoursofthemorning(thewindowofcircadianloworWOCL)thatoccursaround

35amformostpeople.Note:thesetwoprocessesarethemaincomponentsinmostofthebiomathematicalmodelsthatareusedtopredictcrewmemberfatiguelevels(seeChapterFour).


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OperationalNote:KeyFactsAboutTheCircadianBodyClock

Thecircadianbodyclockisapacemakerinthebrainthatissensitivetolightthroughaspecializedinputpathwayfromtheeyes(separatefromvision).

Thecircadianbiologicalclockgeneratesaninnatebiologicaldaythatisslightlylongerthan24hoursformostpeople.Itssensitivitytolightenablesittostayinstepwiththe24hourday/nightcycle.

Almost

every

aspect

of

human

functioning

(physical

or

mental)

undergoes

daily

cycles

that

are

influencedbythecircadianbodyclock. Thedailyminimumincorebodytemperaturecorrespondstothetimeinthecircadianbodyclockcycle

whenpeoplefeelmostsleepyandareleastabletoperformmentalandphysicaltasks.ThisissometimescalledtheWindowofCircadianLow(WOCL)anditisatimeofhighriskforfatiguerelatederror.

ShiftWork

Shiftworkcanbedefinedasanydutypatternthatrequiresacrewmembertobeawakeduringthetimeinthecircadianbodyclockcyclethattheywouldnormallybeasleep.

Theabilityofthecircadianclocktolockontothe24hourday/nightcyclemakesitresistadaptationtoanypatternotherthansleepatnight.

Thefactthatthecircadianbodyclockdoesnotadaptfullytoalteredsleep/wakepatternshastwomainconsequences; dutydays thatoverlapcrewmembersusual sleep times (particularlyallnightoperations) tend to

causesleeprestriction;and crewmemberswhoareworkingthroughthewindowofcircadianlow(WOCL)canbeexpectedtobe

sleepyandhavetomakeadditionalefforttomaintaintheirperformance. Thefurthersleepisdisplacedfromtheoptimumpartofthecircadianbodyclockcycle,themoredifficult

itbecomesforcrewmemberstogetadequatesleep. Inscheduling,thefrequencyofrecoverybreaks(atleast2consecutivenightsofunrestrictedsleep)

needstoreflecttherateofaccumulationofsleepdebt.

JetLag Flying across time zones exposes the circadian body clock to sudden shifts in the day/night cycle.

Becauseof itssensitivityto lightand(toa lesserextent)socialtimecues,thecircadianbodyclockwill

eventuallyadapttoanewtimezone. Therateofadaptationdependsonthenumberoftimezonescrossed,thedirectionoftravel(fasterafter

westwardflights)andtheextenttowhichthecircadianbodyclockisexposedtothe24hourcuesinthenewtimezone(outdoorlight,sleepingandeatingonlocaltime,etc).

Layoversof2448hoursarenotlongenoughtoallowthecircadianbodyclocktoadapttolocaltime. Differenttypesoflonghaultrippatternsaffectthecircadianbodyclockindifferentways.

Sequencesofbacktobacktransmeridian flightsthatdonotreturnto thedomiciletimezone forlongperiodsoftimetendtocausethecircadianbodyclocktodriftonitsinnatecycle.Onreturntothehometimezone,additionaldaysareneededtoreadapttolocaltime.

Sequences of outandback transmeridan flights that return to the home time zone on alternatelayoversseemtoenablethecircadianbodyclocktoremainsynchronizedtothehometimezone.

Ontripsthatincludelongerperiodsinthedestinationregion,forexampleseveraldaysoflocalflying

before

the

return

flight

home,

the

circadian

body

clock

begins

to

adapt

to

the

destination

time

zone.

Thismay improve layoversleep.On theotherhand,on return tothehome timezone,additionaldaysareneededtoreadapttolocaltime.

On long haul layovers, sleep is affected by competition between physiological processes (thehomeostaticsleepdriveandthecircadianbiologicalclock)andapreferenceforsleepingduringthelocalnight.

Routespecific recommendations for personal fatigue mitigation strategies may be useful in FRMStrainingforlonghaulandULRcrewmembers.


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OperationalNote:HowMuchSleepin24hoursisEnough?

This common question is usually aimed at trying to get a magic number for the minimumamount of sleep that a crewmember needs, or the minimum rest period that needs to be

scheduled. From a sleep science perspecti

8. frms implementation guide ~ draft

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