Preliminary Analysis of Parameters for Pilot Fatigue Detection Based on Aircraft States Measurements

Tests were performed on a 6 degrees-of-freedom flight simulator with three different pilots at two extreme levels of alertness with the objective to identify parameters based on aircraft states measurements that can serve as pilot fatigue on-line detectors. A limited number of typical steady state flight conditions were analyzed. Parameters based on the statistics of the tracking errors were defined and their performance as fatigue detectors assessed. The Fourier transforms of the measurements were analyzed to put into evidence changes in the pilot+aircraft system as a result of fatigue. The parameters investigated showed promising capabilities to be used as pilot fatigue detectors within safety monitoring schemes and fault-tolerant control laws. measurements have been developed in the early 70's. Several other methods 7-9 emerged later based on composite indexes computed using quantitative performance parameters and self-assessments. More recently, significant efforts were directed towards the modeling and prediction of human operator error 10-13 in an attempt to reduce incidents by improving the infrastructure (e.g. runway markings and signs, cockpit instrument display and location). Based on the analysis and the statistics of aviation incidents as well as on advances in understanding the cognitive and decision making processes, aspects of the human operator behavior like memory access, situational awareness, and distributed attention were modeled and used in simulations. It has been recognized that all these factors and, implicitly, the performance and safety of piloted flight can be degraded by fatigue and reduced alertness. According to the definition 14 by the International Civil Aviation Organization (ICAO), "fatigue may be considered to be a condition reflecting inadequate rest, as well as a collection of symptoms associated with displaced or disturbed biological rhythms". A model has been developed by the QinetiQ Centre of Human Sciences 15 (CHS) that relates levels of alertness on a scale of 0 to 100 to time of day on waking and time since last main sleep. Such research efforts relied primarily on subjective assessments of alertness/fatigue and were directed towards identifying the factors that contribute to fatigue occurrence. The effects of fatigue on measurable aircraft control performance parameters have only been addressed 15 in a limited manner mainly due to the use of simple synthetic tasks and simplified test environments that only partially reflect the complexity of actual piloted flight. The real-time evaluation of fatigue levels attempted so far relies only on physiological measurements 15,16 (such as electrical activity of the brain, pulse, body temperature, etc) which imply direct and permanent connection of the pilot to the measurement system and exhibit large individual variability and high sensitivity to other factors than fatigue. If this approach were to be used for on-line monitoring, the issue of large and heavy additional hardware on-board becomes critical. Fatigue assessment from measurements of pilot/aircraft dynamic parameters has not yet been