Accident Analysis and Prevention 45S (2012) 27–31 Contents lists available at SciVerse ScienceDirect Accident Analysis and Prevention j ournal homepage: www.elsevier.com/locate/aap Sleep and sleepiness during an ultra long-range flight operation between the Middle East and United States a,∗ b a a,c Alexandra Holmes , Soha Al-Bayat , Cassie Hilditch , Samira Bourgeois-Bougrine a Clockwork Research, 21 Southwick Mews, London W2 1JG, United Kingdom b Qatar Airways Medical Centre, P.O. Box 22550, Doha, Qatar c LATI – Laboratoire Adaptation Travail Individu, Université Paris Descartes, 71, Avenue Edouard Vaillant, 92774 Boulogne Billancourt, France a r t i c l e i n f o a b s t r a c t Article history: This study provides a practical example of fatigue risk management in aviation. The sleep and sleepiness Received 3 May 2011 × of 44 pilots (11 trips 4 pilot crew) working an ultra long-range (ULR; flight time >16 h) round-trip Received in revised form 3 August 2011 operation between Doha and Houston was assessed. Sleep was assessed using activity monitors and self- Accepted 11 August 2011 reported sleep diaries. Mean Karolinska Sleepiness Scores (KSS) for climb and descent did not exceed 5 (“neither alert nor sleepy”). Mean daily sleep duration was maintained above 6.3 h throughout the Keywords: operation. During in-flight rest periods, 98% of pilots obtained sleep and sleepiness was subsequently Sleepiness reduced. On layover (49.5 h) crew were advised to sleep on Doha or Universal Co-ordinated Time (UTC), Ultra long-range but 64% slept during the local (social) night time. Pilots originating from regions with a siesta culture In-flight rest Siesta were more likely to nap and made particularly effective use of their daytime in-flight rest periods. The Sleep results indicate that the operation is well designed from a fatigue management perspective. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction between being at the controls and resting (usually) in a bunk facil- ity that enabled crew to sleep in a horizontal position in a quiet, An ultra-long range (ULR) flight operation is defined as “an oper- temperature-controlled, dark environment. Crew were encouraged ation involving any sector between a specific city pair (A–B–A) in to structure their in-flight work and rest schedule so that both the which the planned flight time exceeds 16 h, taking into account operating and relief crew each took two rest periods per ULR flight. mean wind conditions and seasonal changes” (ULR Crew Alertness The Task Force found that on ULR flights where crew used the Steering Committee, 2005). The world’s first commercial ULR oper- proposed in-flight rest structure and the bunk facilities, alertness ation was commenced by Singapore Airlines in 2004 and involves and performance levels were comparable to existing long-haul trans-polar flights between Singapore and Los Angeles (ULR Crew operations (12–16 h flight duration; ULR Crew Alertness Steering Alertness Steering Committee, 2005). Today, other airlines operate Committee, 2005). Taking two rest periods effectively limited ULR routes and many are between the Middle East and the United fatigue by restricting the amount of time pilots were continuously States. at the controls and providing rest periods to alleviate the fatigue From a safety perspective, ULR flights pose a number of poten- caused by time-on-task (Neri et al., 2002). The provision of two rest tial challenges, including the potential for elevated levels of pilot periods per crew has the added advantage of reducing the likeli- fatigue. Before the ULR operation out of Singapore was approved, hood of a pilot obtaining no sleep during a flight. If one rest period a large fatigue management research programme was conducted is disturbed, for example by turbulence, pilots still have another by a ULR Task Force consisting of researchers and representatives period in which to obtain some sleep. from the airline, the local regulator and the pilots’ union (ULR Crew The ULR Task Force stipulated that the research they undertook Alertness Steering Committee, 2005). All ULR routes were oper- was specific to the Singapore operation and every ULR opera- ated by four-pilot crews, each consisting of an operating crew (two tion requires individual validation (ULR Crew Alertness Steering pilots) and a relief crew (two pilots). The crew alternated in-flight Committee, 2005). The aim of the current study was therefore to assess crew sleep and sleepiness during a new ULR operation between Doha (DOH), Qatar, and Houston (IAH), United States. ∗ To assist crew to cope with the ULR operation they were pro- Corresponding author. Tel.: +44 20 7402 6233. vided with detailed guidance on when ideally to sleep, wake, E-mail addresses: [email protected] (A. Holmes), avoid/consume caffeine, avoid/seek light exposure and when to [email protected] (S. Al-Bayat), [email protected] (C. Hilditch), [email protected] (S. Bourgeois-Bougrine). exercise. In previous ULR studies crew have not been provided 0001-4575/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.aap.2011.09.021 28 A. Holmes et al. / Accident Analysis and Prevention 45S (2012) 27–31 with such comprehensive advice. The guidance instructed crew to training or management responsibilities, a significant medical his- arrange in-flight rest such that both crew had two rest periods per tory, or been scheduled to be on leave during the study period. flight. Additionally, in an attempt to promote sleep during layover, Individual pilots were invited to participate and those that con- the guidance encouraged crew to sleep and wake on Doha time or sented were arranged into four-pilot crews that then collected data Coordinated Universal Time (UTC) rather than on Houston time as as full crews. Participants attended a training session at which they was expected. were briefed on the design, nature and purpose of the study and Several studies have shown that on layover, although there is were instructed in how to use the study materials. considerable inter-individual variation, the majority of crew tend to have a main sleep period during the local night, supplemented with 2.2. Study design a nap or multiple naps during their base night time (Darwent et al., 2010; Kandelaars et al., 2006; Lowden and Åkerstedt, 1998, 1999). The study was designed according to the recommendations of Most crew usually coordinate their main sleep period with the local the ULR Crew Alertness Steering Committee (which includes the night because this is when the social and environmental drivers ULR Task Force) published in the Flight Safety Foundation’s Flight for sleep are strongest. This strategy is beneficial during extended Safety Digest (ULR Crew Alertness Steering Committee, 2005). layovers of multiple days because it assists crew to rapidly adapt to the new zone. However, sleeping during the local night has the 2.2.1. Data collection period disadvantage of being counter to the underlying circadian rhythms Data were collected on 11 ULR trips (4 study participants crewed in sleep and alertness. each trip) from July to September 2009. Crews collected data across From a purely circadian perspective, there are multiple reasons the same 9-day roster pattern (flight times are scheduled, not why it may not be ideal for crew to sleep and wake on local time actual): when on layover in Houston: (1) many time-zones (eight time- • ≥ zones to the west) are crossed, thereby involving a large shift in the two local nights off ( 48 h off); • timing of sleep and wake; (2) any successful change in sleep and outbound daytime flight (Doha time): • wake timing must be reversed upon return to Doha; (3) the layover depart Doha 09:50 h – arrive Houston 02:10 h (16.3 h flight is too short (49.5 h) to enable pilots’ underlying circadian rhythms duration); • to adapt to the Houston light and dark cycle; and (4) the outbound layover in Houston (49.5 h); • flight departs at 20:30 h (Houston time) and operates through the return night flight (Houston time): • Houston night. depart Houston 20:30 h – arrive Doha 11:40 h (15.2 h flight This study therefore explored the possibility that providing crew duration); • with guidance on how to sleep and wake on Doha or UTC time could three local nights off. assist crew to maximise sleep during their layover in Houston. Sleep on UTC was advised as it was predicted that maintaining Doha time During the study, the time-zone in Doha was UTC +3 h and Hous- would be difficult for crew. Therefore a slight shift to UTC, rather ton was UTC −5 h, thus the flights crossed eight time-zones. than a full shift to Houston time, was the next preferred option. In addition, the study also explored the possibility that sleep and 2.2.2. Aircraft and rest environment sleepiness differed between pilots originating from regions with Flights were conducted on two Boeing 777-200LR aircraft a ‘siesta culture’ (a lifestyle likely to incorporate the taking of a equipped with pilot bunk facilities above the cockpit. The bunk nap in the afternoon to supplement night time sleep) and those facility includes two horizontal beds, longitudinally oriented fore from regions where siesta is less widely practised. The tendency and aft, separated by a wall; and two business class seats. Pilots to take a siesta is thought to be greatest in equatorial regions such are provided with blankets and pillows. Temperature, light and as Southern Europe, Central America, North Africa and the Mid- ventilation can be controlled and the seats include access to the dle East. Research undertaken in Europe has confirmed that siesta onboard entertainment system.