submission - Independent Pilots Association

The effecr of tinp srncc the last slccp is e\en greater rIa sleep debt aJreadl eriscs. An NTSB
hcavy trucks accident analysis (NTSB. 199ó)clearly shous that "back of the clock" driv'ing wir}
a slecp debr ca¡rics a very' high nsk Of 107 single-rehicle rruck a,.'cidents. l- dnvers exceeded
rhc hou¡s of dury. l.íincry-two pcrccot t2ó) of ¡hese had farigue-related acc¡dents. Tle NTSB
report also shows tha¡ 67 pcrccnt of tn¡ck drivers with irregular dury or slecp panerns had fatigue.
rctacd accidcns compared to 38 pcrcent i¡ drivers with rcgular duty or sleep panerns.
Lrrcgulariry resultcd in a decreasc oi I ó houn on average in slccp with a total of only ó.1 hor¡¡s
compared ¡o7.7 hours in rcgular parcrn drivers. Thc f,iTSB report indicatcd that they could not
daerminc wbcrbcr irrcgula¡ dury/slccp pa¡tcrns pcr sc led to fatiguc but sonp experinrcntal dara
s¡pport this notioo. Tbc ñnrl¡ngs of fu NTSB not only for¡¡d shifted slccp pancrus but this shift
was couplcd with slccp loss. Tar¡b ad Bcrgcr (1974), whilc rnai¡taining slæp leogth, shif¡cd
slccp tirm and found thu pcrformacc oo vigilancc, calculatioo t"sks, and rnood werc
significantly irnpaked. funbcrmc, Nicbolson et al. (1983) showcd thu irregular slec/work
resultcd in increasing pcrforrnancc iryairmcots which nas fr¡¡thcr incre¿scd by tinre on task.
cumulative slccp loss. and working through thc ci¡cadia¡ nadi¡.
Performancc cån also bc afTecfcd b1'cumuluive fatigue buildup across multiple days. Gundel
( 1995) found rhat pilots flying rwo coosccutive nighs wit! 24 hor¡¡s bctwecn fligba slept about
rwo and a half bours less during tbcir daytirnc layovcn (8.6ó hours versus ó.15 hours), and
cxpcrienccd a signiñcant dccline i¡ alcrmss on thc sccood night flight. Alerbcss during tbc fint
si¡ hou¡s in both fligbts appcaren o bc thc sarrE. Tbe laucr part of the sccood flight showed
i¡creascd dcsyochroniz¿tion of EEG dpha wave activir.v, i-odicating lo'*'er levels of alertness.
Spontaneous dozrng indicared an i¡crea-d susceptibilrry sleep. Subjectrvely. pilos felt grearer
farigue on the sccood night. Tbercfore. wrth ti¡rrc since auake berng the sarnc. slerp qualir.v and
quantiry during tbc da¡ime layover rcsultcd in i¡cre¿scd fatrgue.
Samel et al. (1997) monitored I I rugbt flight rotations from Frankfon to Ifa}e/Seychelles
crossing th¡ec ti¡nc zones. Piloa slept on average eight hwrs on base l-lne nighu. On lavover.
sleep *as reduccd to ó.3 bou¡s. Pil..ts amved at SEZ after ll hor.¡¡s of beLng ar*ake (except for
approximaæ 1.5 hou¡ nap pnor todepamrre.t Fatigue scores increased orerboth outbound a¡d
i¡bound flighs *'ith ll.-l mrcro-slecps pcr pilot outbouod and2a.7 on rerurn. Prior to the
outbound FRA-SEZ flight 85 pcrccnt of piJos felt rcsted *hereas on rÊturn onJy 30 percent
reported feeling so. Thesc srudlcs docurncnt t-hu night fìrgbs a¡e associated r*ith reduced sleep
quantity and qualiry, and arÊ accompanied by cumuluire sleep debt.
Borowsþ a¡ld WaIl (1983) found t-hat flight-related accidents in \ar'¡ aucraft xere significantly
higher in flighs originating bct*'ec¡ 2400 and 0600 hou¡s. The hrgher nushap incidence was felt
ro be the result of ci¡cadian desyncbronizaúon and disrupted sleep-u'ake *'cle. Sharppell and
Nen ( 1993) divided the operational day of nary pilos in Desert Shield and Dese rt Storm
operations in to fou¡ quartiles bep-oning al 060l-1200 uitì 0001 to 06O0 beine the fourtl¡
quartile. They found that therc tras a progr€ssive incre¿se in pilots' subjectrre need for rest
tre rween flighs as flights originated later a¡d later in the da¡ from quartile I to quartile 4. In
Uterature Reyiev' Page ?6