SOS_Fatigue_Article.pdf

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Human Fatigue in Aviation Operations

Basics of Fatigue

Fatigue is defined as a non-pathologic state resulting in a decreased ability to

maintain function or workload due to mental or physical stress . Fatigue, by itself, is not thedanger. The threat to safe aviation operations arises from the impairment to alertness and

degradation of performance. Todays global aviation system demands a constant 2!houroperational structure. "ilots, cabin cre#, maintenance personnel, and AT$ staff must #or% incon&unction #ith this around!the!cloc% schedule. This re'uirement introduces stressfulphysiological challenges. These challenges affect productivity, performance, and safety. Byac%no#ledging these challenges, an aviation organi(ation can promote safe and efficientoperations. )f organi(ational procedures and policies ignore these challenges, the potential forcostly incidents and accidents becomes very real.

Humans have an inherent biological need for sleep. *e are genetically

programmed #ith a circadian pacema%er that promotes us to sleep at night and be a#a%eduring the day on a 2!hour schedule. Around!the!cloc% operations pose a challenge to thesebasic physiological principles. +uch operational concerns as shift#or%, changing #or%schedules, multiple time (one transitions, etended periods of #a%efulness, and sleep loss cancause sleep and circadian disruptions that greatly enhance the opportunity for an incident or

accident. The resulting degradation in performance can erode the critical safety margin inaviation operational systems.


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-esearch has found that sleep is a comple and active physiological

state. *hen deprived of sleep, the brain generates the response of sleepiness. This signalprompts the individual to obtain sleep, as the physiological need has not been met. )f deprivedof sleep for long enough, the brain can spontaneously shift from #a%efulness to sleep, in anuncontrolled fashion. The more fatigued the person is, the more rapid and fre'uent theintrusions into #a%efulness these sleep episodes #ill be. These intrusions can be very shorti.e. microsleeps, lasting only seconds/ in duration, or they may be as long as several minutes.+pontaneous sleep episodes severely degrade performance, perhaps even at critical timesapproach and landing after an etended flight segment, AT$ surge at a busy airport, aircraftmaintenance during night shift, etc./.

"erformance degradation induced by fatigue results in negative effects to vigilance, reactiontime, memory recall, psychomotor coordination s%ills, information processing capabilities, anddecision!ma%ing s%ills. As fatigue levels increase, even despite increased effort, poorerperformance is still demonstrated. )f fatigue is not countered, uncontrolled sleep episodes maybe eperienced by affected #or%ers. These events can result in the total loss of capability toperform. +ome recent sleep research has related performance degradation by e'uating it toBlood Alcohol $oncentration BA$/. After 01 hours of

sustained #a%efulness, cognitive performance decreases to a level e'uivalent to theperformance impairment observed at a blood alcohol concentration of .34. This is theproscribed level of alcohol intoication in many #estern industriali(ed countries. After 2 hoursof sustained #a%efulness, cognitive performance decreases to a level e'uivalent to theperformance deficit observed at a blood alcohol concentration of roughly .04. FAAregulations prohibit operation of an aircraft #ith a BA$ of .4 or higher. This vie#pointclearly illustrates the severe ha(ards associated #ith fatigued personnel conductingoperations.


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*e are a nation of sleep deprived #or%ers. 5stimates suggest that many adult Americans aregetting from 0. to 0.3 hours less sleep per night than needed. *ee%ly sleep debtaccumulations of 3. to 1.3 hours are therefore possible. *e attempt to recover from this sleepdebt by 6sleeping in7 on #ee%ends or other off!duty days. Here again, recent researchindicates that countering this sleep deficit is not as easy as simply etending our sleep periods.

After attempted sleep deficit replenishment, the bodys circadian rhythm allo#s sustainedperformance until &ust after the period bet#een 8 p.m. and 3 p.m. "ast that time frame, thelevel of performance severely degrades. $ancellation of a sleep debt re'uires obtaining adeeper sleep for one to t#o nights along #ith an increase in sleep duration.

Fatigue and Aviation Accidents

Human fatigue has been indicated as a causal factor in some significant aircraft accidents. )thas been estimated that fatigue contributes to 2!84 of transport accidents. )n commercialaviation operations, about 14 of fatal accidents are related to human error, therefore the ris%of cre# fatigue contributes to about 03!24 of the overall accident rate. The follo#ing list notessome aircraft accidents that #ere found to involve fatigue9

0::8 ;alitta )nternational, 0F at ?uantanamo Bay, $uba

0::1 ;orean Air, 11!8 at ?uam

0::: American Airlines, @

2 @; Airlines, 11!2F at Halifa, ova +cotia 2 $orporate Airlines, BA5 Cetstream80 at ;ir%sville, D+A

2 @ed Air, ear&et83A at +an Bernadino, $A

23 oganair, B! )slander at @achrihanish, D;

2>, 21th Aug, $omair, $-C0 at eington, ;E

21, 23th Cune, $athay "acific 11F at +toc%holm, +#eden

21, 2=th Oct, Cet, 181!=TF!CF ;eflavi% airport, )celand


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The 0::8 crash of a

;alitta )nternational 0F at ?uantanamo Bay, $uba in 0::8 is generally accepted as thefirst accident in history for #hich pilot fatigue #as cited as one of the primary causes. The pilotstalled a perfectly serviceable aircraft into the ground on approach. His inability to monitor theaircrafts safe flight #as found to be as the direct result of fatigue. The T+B stated thefollo#ing as the primary cause for the crash9 6The impaired &udgment, decision!ma%ing, andflying abilities of the captain and flight cre# due to the effects of fatigueG the captains failure to

properly assess the conditions for landing and maintaining vigilant situational a#areness of theairplane #hile maneuvering onto final approachG his failure to prevent the loss of airspeed andavoid a stall #hile in the steep ban% turnG and his failure to eecute immediate action to recoverfrom the stall.7 The cre# had been on duty for 0= hours, flo#n for nine hours, and #as sufferingfrom circadian rhythm desynchroni(ation. )n 0:::, an American Airlines @

After touchdo#n, the aircraft overran the run#ay and bro%e up, resulting in the deaths of the

captain and ten passengers. These events are &ust t#o of the many aircraft accidents in #hichinvestigators determined fatigue to be causal.

Fatigue @anagement and $ountermeasures

@anagement of fatigue re'uires an integrated program that addresses the re'uirements of allinvolved in an operational environment. @anagement commitment, education and training, andprogram implementationImanagement constitute some of the components of a successfulfatigue management program. As #ith any safety management program, the initiative toaddress fatigue must have un#avering and visible support from the highest levels of

management. +ufficient resource allocation must be dedicated to ensure the success of aprogram. +enior eecutives need to be involved #ith the formulation and management of theirorgani(ations fatigue program. 5ducation and training provide the %no#ledge to support andenable an effective program at all levels of the organi(ation. The education for all personnellevels must encompass fatigue basics, clear recommendations for countermeasures, andprovide industry!specific information. All personnel need to understand ho# their function in theorgani(ation interfaces #ith the countermeasures program. Fatigue management programsre'uire periodic evaluation and refinement. "rogram effectiveness metrics should be analy(ed


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process inputs such as duty schedules, personnel rest periods, and other factors and thenproduce output that indicates personnel effectiveness. This output is then used to develop dutyschedules that minimi(e fatigue!induced safety events. The Fatigue -esources section belo#provides lin%s to t#o of these companies the lin%s to the soft#are providers belo# in no #ayconstitute an endorsementG the references are strictly for informational purposes only/. *iththe current accumulated body of fatigue research and an F-@+ program, safety managementpersonnel of airlines, flight training units, AT$, and maintenance can no# establish effectivefatigue countermeasure programs.

Fatigue -esources

FAA Fatigue $onference "roceedingshttp9II###.faa.govIaboutIofficeJorgIhead'uartersJofficesIavsIofficesIafsIafs2ImediaIaviation

JfatigueJsymposiumIaviationJfatigueJsymposium.pdf5A+A!+ponsored -eporthttp9II###.easa.europa.euI#sJprodIrIdocIresearchIFT42+tudy42Final42-eport.pdf-ebuttal to the 5A+A -eport

http9II###.ryanair.comIdocIne#sI2:Imar:>1.pdfTransport $anada Fatigue -is% @anagementhttp9II###.tc.gc.caIcivilaviationIsmsIfrmsImenu.htmA+A K Teamhttp9IIhuman!factors.arc.nasa.govI(teamI

Alertness +olutions )nc.http9II###.alertness!solutions.comIinde.html

F-@+ +oft#are these firms offer F-@+ soft#are, some on a free on a trial basis/http9II###.flya#a%e.orgI

http9II###.novasci.comIindeJfilesIpage8.htmFAA Fatigue A-$ and *ithdra#al of FAA Fatigue "-@http9II###.faa.govIaboutIofficeJorgIhead'uartersJofficesIavsIofficesIafsIafs2ImediaIflightJandJrestJarc.pdf

http9II###.faa.govIaboutIofficeJorgIhead'uartersJofficesIavsIofficesIafsIafs2ImediaIfati'ueJarcJmembers.pdf

http9II###.faa.govIne#sIfactJsheetsIne#sJstory.cfmLne#s)dM>1>2http9IIedoc%et.access.gpo.govI2:IpdfI5:!2=3.pdf

A"A FTI


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A"A Fatigue -esourceshttp9IIcf.alpa.orgIinternetIpro&ectsIftdtIbac%grI

A"A Fatigue Homehttp9II###.alpa.orgIportalsIalpaIFT

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SOS_Fatigue_Article.pdf