Pilot Fatigue

What is Pilot Fatigue?

Pilot fatigue is "the state of tiredness that is associated with long hours of work, prolonged periods without sleep or the requirement to work at times that are out of synch with the body's biological or circadian rhythms" (Caldwell & Caldwell, 2003, p.15 2).

Types of Fatigue

  • Acute Fatigue: Short-lived, often caused by insufficient sleep
  • Chronic Fatigue: Develops slowly after longer exposures to fatigue (Occupational Safety & Health Service, 1998 10).

Causes of Pilot Fatigue

  • Inadequate sleep due to circadian or "biological clock" disruptions associated with rotating work and rest schedules and time zone transitions (shift lag and jet lag). For example, during a layover a pilot may attempt to sleep when his mind is telling him to be awake and active and vice versa
  • Extended duty time or long periods of wakefulness leading to increased sleep pressure
  • Night flights and early morning report times that occur during normal periods of sleep. The human brain is 'hard wired' to sleep during dark hours and be awake and active during daylight hours also known as the sleep-wake cycle. Scientific studies have shown that pilot alertness is lowest and circadian-induced fatigue is most pronounced between 0300 and 0500 hours (Caldwell & Caldwell, 2003 2)
  • The requirement to sleep during daylight hours. Sleep taken by night shift pilots during daylight hours is more difficult to initiate and tends to be of a shorter duration than night sleep (Caldwell & Caldwell, 2003 2).
  • Sleep restrictions related to short layovers
  • Pathological sleepiness or sleep disorders such as sleep apnea and clinical insomnia
  • High workload or taxing mental work (especially relevant for short-haul pilots who must perform a greater number of take-offs and landings than long-haul pilots)
  • Mental boredom such as boredom associated with long-haul flights when the autopilot is engaged
  • Stress, anxiety or depression
  • Mild hypoxia (oxygen deficiency)
  • Poor nutrition. For example, dehydration, eating too much causing excess body weight or not eating leading to low blood sugar levels
  • Illness such as influenza (flu) and anemia (iron deficiency)
  • Medication and alcohol (that reduce the quality of sleep)
  • Intentional sleep restriction
  • Inadequate sleep due to uncomfortable sleeping environments
  • Poor sleeping habits such as consuming food immediately before bed and sacrificing sleep for social activities
  • Intense and prolonged physical activity1

Inadequate Sleep

It is estimated that inadequate sleep is the cause of 95 percent of pilot fatigue cases (Caldwell & Caldwell, 2003 2).

Although different individuals require different amounts of sleep, most humans need an average of 8 hours of good quality continuous sleep in every 24 hour period to avoid the onset of fatigue (Campbell & Bagshaw, 1999 3; Ewing, 1993 6). A reduction in sleep by as little as one hour per sleep period can cause fatigue which can become progressively more pronounced with reduced sleep in subsequent periods (Occupational Safety & Health Service, 1998 10). This phenomenon is known as cumulative sleep debt (Beanlands, 2003 1).

Effects of Fatigue on Pilot Performance

Studies have shown that a cause and effect relationship does exist between pilot fatigue and vulnerability to pilot error (Walton, 2003 13). These studies are supported by accident reports citing pilot fatigue as a cause. Examples include Korea Air flight 801 at Guam International Airport in 1999 and American International flight 808 at Guantanamo Bay, Cuba in 1993 (Caldwell & Calwell, 2003 2; Dismukes, Berman & Loukopoulos, 2007 5).

The effects of fatigue on pilot performance include:

  • Cognitive fixation or narrowing of attention causing decreased ability to concentrate on more than task or piece of information. Preoccupation with one task at the neglect of other tasks leads to loss of situational awareness
  • Reduced alertness and vigilance that may degrade situational awareness through failures in monitoring or scanning the flight environment
  • Feelings of indifference or carelessness to operational performance or the outcome of the flight leading to acceptance of lower standards of performance
  • Reduced communications that may hamper crew coordination and effective and efficient Crew Resource Management practice
  • Increased reaction time or sensitivity to time on task
  • Inconsistent performance
  • Short term memory loss and inability to recall information from long term memory. Diminished memory may cause a pilot to forget important Air Traffic Control information
  • Cognitive slowing causing an inability to integrate information efficiently
  • Impaired judgment, logical reasoning and decision making ability. For example, difficulty processing critical information and choosing among alternatives may lead to optimum response decrements or degradations in response accuracy
  • Increased feelings of difficulty in carrying out flight activities. This may cause a pilot to ignore important tasks due to the perception that the tasks are too difficult to manage
  • Degradation in flying and perceptual-motor skills such as hand-eye coordination
  • Impaired ability to judge performance of self and performance of other crew members leading to difficulty recognising performance impairment and situation danger
  • Increased vulnerability to plan continuation error where impaired ability to recognise that a situation is deteriorating makes a fatigued pilot slow to recognise that the original plan of action is no longer appropriate to the situation and must be changed
  • Reduced visual perception
  • Loss of initiative or disinclination for effort
  • Personality or mood changes such as irritability and depression that may deter crew coordination and communication
  • Microsleeps causing brief disengagement from the flight environment2

Strategies to Manage Pilot Fatigue

In commercial aviation, pilot fatigue is (partially) controlled by:

  1. Flight and duty time limitations imposed by regulators (Campbell & Bagshaw, 1999 3)
  2. Companies that commit to not putting pilots in the position of having the fly fatigued (Dismukes et al, 2007 5)
  3. Training programs that educate both pilots and managers in understanding and combating fatigue (Dismukes et al, 2007 5)

However, in all situations if a pilot considers that he or she is too fatigued to fly safely then he or she should act responsibly and choose not to fly. Furthermore, pilots must ensure that they take adequate rest periods and do not exceed the flight and duty time limitations imposed by the regulator.

There are several strategies that a pilot can use to prevent fatigue:3

Outside Flight and Duty Periods

  • Obtain 8 consolidated hours of sleep on a daily basis
  • Practice good sleep hygiene techniques to encourage the onset of good quality sleep:
    • Develop a regular pre-sleep routine
    • Avoid consumption of caffeinated and alcoholic beverages 4-6 hours before bedtime
    • Avoid eating or drinking heavily before bedtime
    • Avoid non-sleep conducive behaviours in the bedroom such as arguments
    • Ensure a comfortable bed and sleeping environment (for example, ensure room is dark, quiet and at a comfortable temperature)
    • Avoid emotional stress, excessive mental stimulation or intense physical exercise immediately before bedtime
    • Promote sleep through light reading, relaxation techniques (such as yoga or meditation) and consumption of a warm milky drink or light snack (if hungry)
  • Maintain a healthy well-balanced diet and regular physical exercise
  • Practice stress reduction techniques to prevent stress-related fatigue
  • Achieve better life organisation. For example, effectively structure life around shift work by adopting strict and consistent sleep-wake regimes and making arrangements with family members
  • Refrain from engaging in intense physical activity immediately prior to a duty period
  • Use short-life sleeping pills as a final resort to counteract shift lag and jet lag and help to resynchronise the sleep cycle (Campbell & Bagshaw, 1999 3). Sleeping pills should only be taken by a pilot if absolutely necessary, following consultation with his or her Aviation Medical Examiner

During Flight and Duty Periods

  • Alternate periods of activity and relaxation during flight or rotate flight tasks
  • Engage in social conversation with other crew members
  • Organise and delegate tasks to reduce mental workload
  • Practice arm and leg stretching or contract and relax muscles during flight (to maintain alertness)
  • Move about the cabin if possible
  • Consume moderate amounts of caffeine if desired
  • Consume food and water regularly to provide the body with energy and prevent the onset of fatigue caused by low blood sugar levels and dehydration
  • Engage in pre-planned naps in multi pilot cockpit environments (where regulations and airline policies permit)
1. Beanlands, P. (2003). 190117 sleep, fatigue and fatigue management lecture notes. Albany: Author.
2. Caldwell, J.A., & Caldwell, J.L. (2003). Fatigue in aviation: A guide to staying awake at the stick. England: Ashgate Publishing Ltd.
3. Campbell, R.D., & Bagshaw, M. (1999). Human performance and limitations in aviation (2nd ed.). United Kingdom: Blackwell Science Ltd.
4. Costa, G. (1999). Fatigue and biological rhythms. In D.J. Garland, V.D. Hopkin, & J.A. Wise (Eds). Handbook of aviation human factors (pp. 235-255). New Jersey: Lawrence Erlbaum Associates, Inc.
5. Dismukes, R.K., Berman, B.A., & Loukopoulos, L.D. (2007). The limits of expertise: Rethinking pilot error and the causes of airline accidents. England: Ashgate Publishing Ltd.
6. Ewing, R.L. (1993) Aviation medicine and other human factors for pilots. Auckland: David Ling Publishing.
7. Green, R.G., Muir, H., James, M., Gradwell, D., & Green, R.L. (1996). Human factors for pilots (2nd ed.). England: Ashgate Publishing Ltd.
8. Keightley, A. (2004). 190216 human factors study guide. Palmerston North: Massey University.
9. Natelson, B.H. (1998). Facing and fighting fatigue: A practical approach. USA: Yale University Press.
10. Occupational Safety & Health Service. (1998). Stress and fatigue: Their impact on health and safety in the workplace. New Zealand: Author.
11. Reinhart, R.O. (1999). Fit for flight: Flight physiology and human factors for aircrew (2nd ed.). Iowa: Iowa State University Press.
12. Stokes, A., & Kite, K. (1994). Flight stress: Stress, fatigue and performance in aviation. England: Ashgate Publishing Ltd.
13. Walton, A.J. (2003). Flight and duty times of flight instructors in general aviation in New Zealand: A study. Massey University, Auckland, New Zealand: Author.

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NASA - Fatigue Countermeasures
This website provides further information related to fatigue management in aviation

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