The Effects of Sleep Deprivation on Flight Performance, Instrument Scanning, and Physiological Arousal in Pilots

Abstract

The effects of 34 hr of continuous wakefulness on flight performance, instrument scanning, subjective fatigue, and EEG activity were measured. Ten fixed-wing military pilots flew a series of 10 simulator profiles, and root mean squared error was calculated for various flight parameters. Ocular scan patterns were obtained by magnetic head tracking and infrared eye tracking. Flying errors peaked after about 24 to 28 hr of continuous wakefulness in line with peaks in subjective fatigue and EEG theta activity, and they were not directly attributable to degradation of instrument scanning, which was very consistent across pilots and largely unaffected by the sleep deprivation.

Notes

¹Three of our pilots had just completed undergraduate pilot training.

²One pilot misplaced his sleep log and failed to return it.

³In an additional segment, which was too variable to allow commanded parameters, the pilot was required to achieve and maintain a heading at 45° to intersect final approach.

⁴Dwell time refers to the amount of time spent continuously in one area of interest, whether in multiple fixations or not. The 2 sec criterion for long dwell times was based on the fact that, in preliminary data, less than 10% of all dwell times were greater than that value.

⁵Only one eye-movement record was salvageable from the tenth pilot, but it was not statistically analyzable because there were no other records from that pilot. Hence, all of that pilot's gaze data were discarded.

⁶Because the flight times were staggered by 1 hr for the two pilots, the session times in the data figures (next section) are listed as 1230, 1530, 1830, and so on.

⁷It is conceivable that greater flight performance decrements could have occurred in transitioning from one flight segment to another, as we only measured flight performance once the criteria (e.g., a certain bank angle, heading, or airspeed) for entering a maneuver had been met. Fatigue-induced degradation in pilot performance could have prolonged the time required for a pilot to achieve the proper parameters initially and thereby would have been reflected in the total of amount of in-flight data collection time relative to the total time of flight. However, the percentage of data collection time lost due to transitioning varied only slightly across the 10 sessions, from a high of 51.3% in Flight 1 to a low of 48.8% in Flight 2.

⁸Microsleeps were determined visually (e.g., prolonged eye closure) and were rare overall in that only six instances in three pilots were recorded during the course of the entire study.

⁹In total darkness, for example, baseline pupil diameter typically runs between 7.0 and 7.5 mm (Wilhelm et al., 1998; Yoss et al., 1979), which would have allowed more room for decrease.