Jonathan French

SUBJECTIVE FATIGUE OF C-141 AIRCREWS DURING OPERATION DESERT STORM

Airlift crews were exposed to extended work periods, reduced sleep periods, night work, and circadian dysrhythmia caused by shift work and time-zone crossings during Operations Desert Shield and Desert Storm. This research reveals the extent to which severe subjective fatigue was experienced by the crews during Operation Desert Storm. In addition, through the evaluation of long-term and short-term work and sleep histories, this research shows that recent sleep and flight histories are correlated with high fatigue levels. Furthermore, we found a tendency for fatigue to correspond with pilot error. We recommend that the training of personnel involved in long-duration operations include fatigue management strategies and, further, that work policies and environments be designed to take into account the importance of regular and restorative sleep when unusual duty hours are required.

The Sleepiness-Induced Lapsing and Cognitive Slowing (SILCS) Model: Predicting Fatigue Effects on Warfighter Performance

The Sleepiness-Induced Lapsing and Cognitive Slowing (SILCS) model is designed to improve the credibility and accuracy of synthetic warfighters used in high fidelity simulation systems. The empirically derived SILCS model describes sleep deprivation and time-of-day effects on performance in terms of the influence of two phenomena - general response slowing and lapsing. The former produces small increases in response time while the latter causes significant increases and errors.

The Prediction of Cognitive Performance Degradations during Sustained Operations

Opportunities for fatigue related accidents are greatest when extended duty cycles must be maintained. A means to plan for the influence of fatigue would be useful to best utilize crew resources. Equations were derived to predict performance degradations associated with fatigued cognitive abilities. During a 30-hour sleep deprivation study, nine male subjects were required to perform a 45-minute cognitive performance battery every 120 minutes. Plasma melatonin levels also were obtained. Cognitive performance measures sensitive to fatigue were determined and used to derive composite response time and accuracy scores. The equations that best described the composite scores included a linear component (hours awake weighting) and a circadian component (melatonin weighting). The respective prediction equations accounted for 33% of the variance in response time performance (p < .0001) and 18% of the variance in accuracy performance (p < .0005). Tests on the beta weights indicated that accuracy predictions were more enhanced by the circadian component than were those for response time. This work represents a mathematical description of fatigued performance that is sensitive to circadian cycles and requires minimal input data. The results might be used to recommend the best crew rest times and when additional crew should be employed as individual performance falls below critical thresholds during sustained operations.

A Study of the Effects of Repeated 36-Hour Simulated Missions on B-1B Aircrew Members

The military goal of Global Reach - Global Power entails an unprecedented dependence on immediate and sustained long range bombing campaigns. This research effort was initiated to evaluate the feasibility of this type of long range operation by studying the effects of multiple long duration missions on bomber aircrews. Measures of cognitive performance, mood, fatigue, and sleep management suggest that crews learned to adapt to the missions. However, cognitive performance deteriorated during the early morning hours of each mission and expert ratings of flight deck performance suggest that some components of performance may have been negatively impacted by the repeated missions. This research contributes to the base of information that may be used to make operational risk decisions and suggests ways to reduce schedule-related risks. It also explores the effects of sustained operations on complex tasks, as well as on simple tasks, and explores the use of multiple data collection techniques in a non-laboratory setting.

Sleep and Flight Duration Effects on the Subjective Fatigue of Pilots during Operation Desert Storm

Subjective fatigue of 11 C-141 pilots serving in the United States Air Force Military Airlift Command (MAC) during the Desert Storm campaign was assessed in a 30-day field study. Subjective fatigue measures were obtained from pilots at the beginning and end of each duty day using the Profile of Mood States (POMS) fatigue dimension. Also, a 7-point fatigue rating was recorded every 4 hours. The two fatigue measures were each evaluated with respect to (1) 48-hr cumulative flight time, (2) 48-hr cumulative sleep time and (3) 30-day cumulative flight time. The data indicate that at least 15 hours of sleep per 48-hr time period is needed to avoid pilot fatigue. Recent flight time was also found to be related to subjective fatigue, but this relationship seems rooted loss of sleep during long flights. Cumulative 30-day flight time, which is the measure currently used to regulate flight hours, was not related to increases in subjective fatigue.