Aviation is challenging and rewarding and it is also fatiguing. There are so many ways that flying can be fatiguing that we have to define what aspect we are referring to.  There are Part 117 definitions, due to lack of sleep or over exertion. There are physiological impacts such as lower oxygen levels or vibration. Then there is mental fatigue, a physiopsychologiocal product of focused attention over time.

Mental fatigue is perhaps the most overlooked human factor because it is largely invisible and develops internally. Mental fatigue is often ignored as an aspect of error causality. Current research gives us a window for understanding and identifying mental fatigue. Neuroscience has made great strides in mapping brain function and disfunction. In aviation we should focus on the processing capability of the pilot when exposed to mental fatigue.  Studies have identified that concentrated focus, engaging visual perception and processing can cause changes in brain function described as mental fatigue.

Two of the discovered impacts are of primary concern in the cockpit. First, the ability to process and analyze information is degraded. It takes longer to recognize what is happening and then produce an appropriate response.  Secondly, the brain uses memory to create relevancy filters. When stimulus is received, the brain uses these relevancy filters to disregard information that is not relevant to solving the current problem. Mental fatigue has been shown to degrade the effectiveness of relevancy filters. This allows irrelevant information in to the processing chain at a time when it is already overloaded, resulting in greater performance error potential.

We have often described this condition as fixation, task saturation, or tunnel vision without understanding why it occurred. What is important is that we now can find ways to prevent, rather than just identify and mitigate. In addition, mitigation now can be by design, like slowing down procedures during times of mental fatigue potential. We have made great strides in producing Human Factor strategies and reducing traditional fatigue threats.  Now is the time to go deeper and explore the limits of our physiopsychological ability to manage automation and the complex ATC environment.