Comparison of in-flight measures with predictions of a bio-mathematical fatigue model.

INTRODUCTION: Bio-mathematical models are increasingly used for predicting fatigue in airline operations, and have been proposed as a possible component of fatigue risk management systems (FRMS). There is a need to continue to evaluate fatigue models against data collected from crews conducting commercial flight operations.

METHODS: A comparison was made between several in-flight studies of pilot fatigue, conducted over a 10-yr period on a variety of operations, and the predictions of a widely used bio-mathematical model, the System for Aircrew Fatigue Evaluation (SAFE). The in-flight studies collected a variety of subjective ratings as well as reaction time on a performance task.

RESULTS: Overall correlation between observed and predicted fatigue was stronger for subjective fatigue than reaction time. More detailed analysis on selected studies shows discrepancies between predicted and observed fatigue, which may be explained by a variety of confounders. Closer analysis of the duty time, time of day, and schedule length show discrepancies of up to 15% between observed and predicted fatigue.

DISCUSSION: This study provides comparison between the predictions of one bio-mathematical model, SAFE, and observed fatigue measures across a number of operations. Possible causes of discrepancies are discussed. There is potential for more comparison studies of this type with the various available models.