Significance of time awake for predicting pilots' fatigue on short‐haul flights: implications for flight duty time regulations

Jul 22, 2014Journal of sleep research

Time Awake and Its Role in Predicting Pilot Fatigue on Short Flights: Implications for Flight Duty Rules

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Abstract

Pilots finishing late at night reported higher fatigue levels despite having 1.1 hours more sleep than those starting early in the morning.

Fatigue levels were studied in 40 commercial short-haul pilots over 188 flight duty periods.
Pilots completing late flights (00:00-01:59 hour) experienced greater fatigue than those starting early (05:00-06:59 hour).
The average time awake before late duties was 5.5 hours longer than for early duties (6.6 hours versus 1.1 hours).
Linear mixed-model regression indicated that time awake is a significant predictor of fatigue.
Late-finishing flights coincide with reduced alertness from the circadian system, suggesting an underestimated fatigue risk.

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European regulations restrict the duration of the maximum daily flight duty period for pilots as a function of the duty start time and the number of scheduled flights. However, late duty end times that may include long times awake are not specifically regulated. In this study, fatigue levels in pilots finishing their duty late at night (00:00-01:59 hour) were analysed and compared with pilots starting their duty early (05:00-06:59 hour). Fatigue levels of 40 commercial short-haul pilots were studied during a total of 188 flight duty periods, of which 87 started early and 22 finished late. Pilots used a small handheld computer to maintain a duty and sleep log, and to indicate fatigue levels immediately after each flight. Sleep logs were checked with actigraphy. Pilots on late-finishing flight duty periods were more fatigued at the end of their duty than pilots on early-starting flight duty periods, despite the fact that preceding sleep duration was longer by 1.1 h. Linear mixed-model regression identified time awake as a preeminent factor predicting fatigue. Workload had a minor effect. Pilots on late-finishing flight duty periods were awake longer by an average of 5.5 h (6.6 versus 1.1 h) before commencing their duty than pilots who started early in the morning. Late-finishing flights were associated with long times awake at a time when the circadian system stops promoting alertness, and an increased, previously underestimated fatigue risk. Based on these findings, flight duty limitations should consider not only duty start time, but also the time of the final landing.

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Significance of time awake for predicting pilots' fatigue on short‐haul flights: implications for flight duty time regulations

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