Rosekind, M. R., Gregory, K. B., Miller, D. L., Oyung, R. L., Neri, D. F., Dinges, D.F., (1997). Sleep Quantity and Quality of Augmented Long Haul Flight Crews in On-Board Crew Rest Facilities. Sleep Research, 26, 41.
Introduction. Modern long-haul aircraft have the capability to fly more than 14 continuous hours aloft. Federal flight/duty/rest regulations require that extra (augmented) flight crew be on board for extended flight lengths beyond 12 hr. The primary flight crew rotate with the augmented crew to manage flight responsibilities and to utilize on-board crew rest facilities (bunks) inflight. An initial survey study was conducted to examine the self-reported quantity and quality of sleep obtained in on-board crew rest facilities, factors that promoted or interfered with sleep, and the effectiveness of the sleep opportunity to promote performance and alertness (ref. 1). Following this initial survey study, a field study was conducted to obtain inflight physiological measures of sleep quantity and quality in the rest facility and to examine subsequent alertness and performance.
Methods. This field study involved thirty-eight long-haul flight crewmembers (mean age = 46.5 yr) monitored during two different regularly scheduled international trip patterns with flights (average duration 13 hr) crossing 4-8 time zones. Pattern I involved trans-pacific flights from San Francisco to Hong Kong or Sydney; Pattern II involved north-south flights from Taipei (Taiwan) to Auckland or Christchurch (New Zealand). Rest periods were scheduled on a rotating basis during the low-workload cruise portion of flight.
There were three types of aircraft used in these operations: Boeing 747-200, 747-400, and 767-200/300. Each of the aircraft have a different crew rest facility configuration. In the 747 aircraft a permanent rest facility is located aft of the flight deck with both an upper and lower bunk. In the 767 aircraft a convertible semi-permanent rest facility is situated between the business and economy class cabin. In all bunk facilities, pillows and wool blankets are available. The 747-400 operations had two crew members sharing use of the rest facility at the same time.
A comprehensive range of physiological, performance, behavioral, self-report, and environmental measures was employed in the field study. Background questionnaires distributed prior to the trip gathered information such as basic demographics and sleep history. Using an AIRLOG, an electronic sleep/wake diary (ref. 2), flight crews collected self-report data prior to the trip, throughout their duty period, and post-trip. During this same time period, actigraphy was used to provide an estimate of the 24-hour sleep/wake pattern. Continuous ambulatory physiological recordings (Medilog 9000-II), using standardized polysomnographic procedures, were obtained to determine flight crew sleep quantity and quality in the rest facilities. To assess vigilance and performance, a test battery (ref. 3) that consisted of a simple reaction time test (psychomotor vigilance task) and probed recall memory was performed at selected points during the duty period. Environmental measures were obtained in the rest facility during the bunk periods, including sound pressure levels and temperature/humidity.
Results. The average flight duration between the operations differed
by only about 30 min, however, due to rostering strategies the bunk and
sleep periods were significantly different in duration (p<.001). In Pattern
I, the crew consisted of two primary and two augment flight crew. Two bunks
were available that allowed two bunk periods. In Pattern II, the
crew consisted of two primary flight crew and a single augment crewmember.
The aircraft was configured with one bunk and each crew member was allowed
one bunk period. Data were collected for a total of 55 bunk periods. A partial
summary of results is presented in Table 1.
Table 1: Partial Summary of Results
| Pattern I | Pattern II | |
| Age (yr) | 48.4 | 44.8 |
| Flight experience (hr) | 13,597 | 11,538 |
| Flight duration (hr:min) | 13:12 | 12:44 |
| TBT (min) | 258 | 108 |
| TSP (min) | 192 | 84 |
| TST (min) | 155 | 70 |
| Latency (min) | 22.6 | 17.2 |
| Awakenings/period | 12.7 | 5.2 |
| Sleep efficiency (%) | 78 | 84 |
| Stage 1 (% TST) | 17.5 | 12.2 |
| SWS (% TST) | 10.8 | 7.4 |
| REM (% TST) | 6.9 | 4.2 |
There were differences in total bunk time (TBT), total sleep period (TSP), and total sleep time (TST) durations between the two patterns. However, when compared as a percentage of total sleep time, there were no significant differences in sleep latency, sleep efficiency (TST/TSP), stage 1, slow wave, or REM sleep. The raw number of awakenings was significantly greater (p<.001) in Pattern I which appears to be related to the longer bunk periods. When the total number of awakenings is examined relative to bunk time available (awakenings/hr) there is no significant difference between the patterns. REM sleep occurred in 31 bunk periods. On 13 occasions, REM sleep began less than 90 min after sleep onset (in 2 cases TST was less than 90 min) but there were no sleep-onset REM periods. Initial analyses of other factors, such as time of day and environmental disruptions, have yielded no significant findings related to the sleep results.
Conclusions. These data demonstrated that long-haul flight crews were able to obtain a good quantity and quality of sleep in on-board crew rest facilities inflight. Further analyses are examining the relationship between on-board sleep and subsequent performance and alertness during long-haul flight operations. As global demand for air travel continues to increase and future aircraft technology permits even longer flight durations, issues related to flight crew sleep, circadian rhythms, and fatigue will be critical to maintain safety and performance.
1. Rosekind, M.R., Miller, D.L., Gregory, K.B., and Dinges, D.F. (1995). Flight Crew Sleep in Long-Haul Aircraft Bunk Facilities: Survey Results. Sleep Research, 524.
2. Rosekind, M.R., Smith, R.M., Gregory, K.B., and Miller, D.L. (1996). NASA AIRLOG: An Electronic Sleep/Wake Diary. Sleep Research, 525.
3. Rosekind, M.R., Graeber, R.C., Dinges, D.F., Connell, L.J., Rountree, M.S., and Gillen, K. (1994). Crew Factors in Flight Operations IX: Effects of Planned Cockpit Rest on Crew Performance and Alertness in Long-Haul Operations. (NASA Technical Memorandum No. 108839). Moffett Field, CA: NASA Ames Research Center.