Pilot fatigue
The International Civil Aviation Organization (ICAO) defines fatigue as "A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload.
"[1] The phenomenon places great risk on the crew and passengers of an airplane because it significantly increases the chance of pilot error.
[2] Fatigue is particularly prevalent among pilots because of "unpredictable work hours, long duty periods, circadian disruption, and insufficient sleep".
[2] These factors can occur together to produce a combination of sleep deprivation, circadian rhythm effects, and 'time-on task' fatigue.
[2] Regulators attempt to mitigate fatigue by limiting the number of hours pilots are allowed to fly over varying periods of time.
[4] Symptoms associated with fatigue include slower reaction times, difficulty concentrating on tasks resulting in procedural mistakes, lapses in attention, inability to anticipate events, higher toleration for risk, forgetfulness, and reduced decision-making ability.
In the tasks that were not as complex, such as reacting to warning lights and responding to automated alerts, it was found that there was a significant decrease in performance during the sleep deprived stage.
"[8] One United States Air Forces study found significant discrepancies regarding how fatigue affects different individuals.
Limitations of the study were: fatigue levels are subjective and research did not attempt to control the number of times pilots had available to respond to the questionnaires.
Levels of fatigue collected were also compared with a validation test conducted on multiple sclerosis patients in Switzerland.
[11] The study consisted of a questionnaire that was posted on a website, Professional Pilot's Rumour network (PPRUNE) and was able to obtain 162 respondents.
As participants, pilots were subject to physiological measures pre-departure and during flight and filled out routine logs recording their times of sleep and awakening.
The second questionnaire also administered during flight, assessed different dimensions including mental, physical and temporal demand as well as performance.
Findings also show that fatigue was greater during night flights because pilots had already been awake for more than 12 hours and would begin duty by the time they were due to go to sleep.
Advantages of self-assessment include that they are quick and easy to administer, can be added to routine checklists and being more descriptive allow pilot to make a better decision.
The polls show that e.g. 92% of the pilots in Germany report they have felt too tired or unfit for duty while on flight deck at least once in the past three years.
Nowadays prevalence of fatigue draws greater attention because of boom in air travel and because the problem can be addressed with new solutions and countermeasures.
"Keep awake" routines do not affect flight safety and their purpose reattain the pilot's full alertness and undivided attention.
These limits differ based on: what type of operation is being conducted, the time of day, and whether the flight is single-pilot or multi-pilot.
One study found that the findings show "a need to raise the level of knowledge within the industry regarding the causes and consequences of fatigue and of processes for its management".
