In-flight sleep as a pilot fatigue mitigation on long range and ultra-long range flights : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Sleep/Wake Research Centre, Wellington, New Zealand

Abstract

Objectives: Long range flights operate around the clock with long duty periods for pilots. To mitigate the effects of fatigue, these flights are operated by augmented crews, providing each pilot with the opportunity for sleep in on-board rest facilities. This thesis used a mixed methods approach to investigate the use of in-flight sleep and the factors that influence it. Methods: Retrospective survey data (291 pilots, five studies) were analysed to provide an overview of pilots’ sleep at home and investigate potential relationships with in-flight sleep. A second project monitored the sleep, fatigue and performance of 35 pilots operating a B767 flight route between Atlanta and Lagos. These projects were supplemented by thematic analysis of pilots’ logbook comments on in-flight sleep (N=123) and on the way they manage their fatigue (N=629). Results: Pilots viewed in-flight sleep as an important fatigue management strategy and actigraphic sleep monitoring confirmed that the B767 pilots made good use of their in-flight breaks for obtaining sleep. Self-ratings of in-flight sleep quality reflected ratings at home, but were usually poorer. Pilots indicated that the type, location and design of rest facilities affected sleep quality and duration, and identified strategies for minimizing sleep disturbances and improving alertness. Comments indicated that prior knowledge of inflight break allocations can influence the planning of pre-trip sleep, use of naps, and in-flight sleep. Actigraphic measures of sleep indicated that the B767 pilots obtained more sleep in the 24 hours prior to departure than during baseline days regardless of their subsequent pattern of in-flight breaks, but it is unclear when they were advised about their break pattern. Ratings of sleepiness and fatigue increased across the B767 flights, but psychomotor vigilance task performance at the start of duty and at top of descent was not associated with prior wakefulness, prior sleep duration or in-flight sleep duration. Conclusions: In-flight sleep is a well-utilized and effective fatigue mitigation strategy that may be supplemented by other strategies such as flight preparation techniques. To further reduce pilot fatigue risk on long range flights, additional research is warranted into the effects of flight preparation techniques and in-flight break patterns.