Sleep loss and circadian disruption created by flight operations can degrade performance and alertness, we all know that. Scientific examination of these psychological/physiological parameters has established a direct relationship between their degradation and errors, incidents and accidents. We all know that, too. Nevertheless, despite that knowledge, fatigue remains an ever present danger in flight operations.
The operational demands of the aviation industry and the growth in global long-haul, regional, overnight, and short-haul operations will continue to increase the 24hour/7days requirement on flight crews. Therefore, shift work, night work, irregular work schedules, unpredictable work schedules, and time zone changes will continue to be commonplace components of the aviation industry. These factors pose known challenges to human physiology, and because they result in fatigue and performance impairment they pose a risk to safety.
Extensive data are available that clearly establish fatigue as a significant safety concern in all modes of transportation and in 24-hr shift work settings. The safety risk posed by human fatigue in transportation has been recognized and addressed over 100 years. Its 24/7 operational demands can easily lead to degradation or impairment in all aspects of human capability particularly cognitive performance including decision-making, attention, reaction time, learning, memory and communication skills. When individuals performing safety-critical functions are affected by fatigue, there is a high risk of fatalities, injuries and environmental hazards as a result of accidents or incidents.
Additionally, there are other associated costs of fatigue, such as the financial costs of reduced productivity and potential liability issues.
On 2006 a study at UCE Birmingham on the effect of fatigue on 162 short-haul pilots reported 75% of the pilots had experienced severe fatigue with 81% considering the fatigue to be worse than two years previously.
On 2012 the European Cockpit Association carried out a survey about self-assess of the level of fatigue experienced by pilots. More than 6.000 European pilots were surveyed between 2010 and 2012 and the results were published as Barometer on Pilot Fatigue. Some of the survey results are:
- Over 50% of surveyed pilots reported having experienced fatigue as impairing their ability to perform well while on flight duty.
- 4 out of 5 pilots reported having coped with fatigue while in the cockpit, according to polls carried out in Austria (85%), Sweden (89%), Germany (92%) and Denmark (93%).
- In the UK (43%), Denmark (50%), Norway (53%) and Sweden (54%) the surveyed pilots reported falling asleep involuntarily in the cockpit while flying. In the UK, a third of the pilots said to have woken up finding their colleague sleeping as well. 65% of Dutch and French pilots stated they have trouble with “heavy eyelids” during flight.
- 70-80% of fatigued pilots would not file a fatigue report or declare to be unfit to fly. Only 20-30% will report unfit for duty or file a report under such an occurrence.
- More than 3 out of 5 pilots in Sweden (71%), Norway (79%) and Denmark (80-90%) acknowledge having already made mistakes due to fatigue, while in Germany it was 4 out of 5 pilots.
On August 2013 was published the study Prevalence of Fatigue in a Group of Airline Pilots based on a 2012 survey of 1500 commercial airline Portuguese pilots, commanders (captains) or first officers between the ages of 20 and 65 who were on active duty and had flown during the previous six months. The assessed their fatigue using the nine-item Fatigue Severity Scale. Some of the results of the study are:
- More than 90 percent reported having made fatigue-related mistakes in the cockpit
- 66% said that they had more than once been so tired that they should not have been at the controls
- Despite they admitted having been fatigued while flying, 82% said they had never reported themselves as “unfit for flight as a result of accumulated fatigue,” and only 11 percent said they had done so only once
- Pilots flying medium- and short-haul flights —typically less than six hours long with multiple legs — reported higher levels of fatigue than those who flying long-haul flights
The US National Sleep Foundation published in March 2012 a 1,087 transportation professionals poll, which included 220 pilots, interviewed about their sleep habits and work performance. Some of the results of the pilot survey are:
- 23% admitted sleepiness has affected their job performance at least once a week
- 20% said sleepiness had caused safety problems on the job
- 37% of pilots reported that their current work schedule did not allow adequate time for sleep
- 50% said they rarely or never got a good night’s sleep on work nights
Human fatigue can have a role in accidents causation by producing performance impairment when the individual is awake, or by inducing microsleeps or producing an uncontrolled and unintentional full sleep episode.