The aviation industry works 24hrs x 7 days x 365 days. Humans need to sleep. Therefore, there is always a human being working in a period of the day where it should be sleeping and/or in a different time zone. Hence, it may occur that pilots might be fatigued when on duty. Fatigue is a human factor hazard, which affects human performance leading to error(s) that can impair the safety of the flight operation, contributing to an aircraft accident. Therefore, fatigue is a flight safety risk.
Fatigue has been cited as a contributing factor in 15 to 20% of worldwide fatal aviation accidents associated with pilot error; fatigue has played a role in the accident causation chain.
Aircraft operators are required to manage the fatigue risk through a Fatigue Risk Management System (FRMS), which aims to ensure that crew members are sufficiently alert so that they can operate to a satisfactory level of performance and safety.
ICAO defines the FRMS as a ‘A data driven means of continuously monitoring and managing fatigue-related safety risks, based upon scientific principles and knowledge as well as operational experience that aims to ensure relevant personnel are performing at adequate levels of alertness.’
There are currently several risk assessment methodologies (qualitative and quantitative) available in the aviation industry to risk assess safety issues and its potential accident scenarios. These methods consider the sequence of clear and objective safety barriers failing, such as aircraft equipment failure, non-compliance of procedures, etc.
There are bio-mathematical models available to predict the fatigue risks. These are based on sleep regulation models, duty start and duty end times, time zones and number of flights performed that output a predictive fatigue risk, using different fatigue and alertness scales. These models also output the expected percentage degradation of the pilot’s reaction, such as reaction time to warnings, acceptance to risk taking, etc. These errors can indeed contribute to an accident when aligned with other factors. But it is not known if having a 43% reduction time in response to a warning how will that contribute to increase the accident risk? What is the correlation between these two risks: fatigue risk vs. accident risk? How should the fatigue risk be factored in the aircraft accident risks models?
This is the current challenge that the aviation industry is experiencing as part of its FRMS and where efforts and focus is.