Understanding How Fatigue Affects Work Performance

Programs can effectively combat fatigue, reducing a leading cause of maintenance errors.

Some years ago, scientists at Harvard Medical School and other top research facilities examined the cumulative costs of sleep deprevation. What they found was startling: When sleep was limited to 6 hr. or less per night over 14 days, it produced cognitive performance deficits equivalent to up to two nights of total sleep loss. Even more alarming, due to the gradual and cumulative nature of the sleep restriction, the subjects studied were largely unaware of their declining performance. In tests, they thought they were doing just fine.

The demographics of study participants likely are similar to those in any MRO organization. Those studied—healthy adults aged 21-38—were chosen because they fit the demographic found in occupations associated with chronic sleep restriction, including shift work. In that age range, it is also common to find other factors leading to sleep deprivation, including raising young children. These factors can quickly add up to a lifestyle that results in chronic sleep restriction without the worker being aware of how it is affecting their performance.

“People think about fatigue as being physically tired,” says Kevin Gregory, vice president/senior scientist at Alertness Solutions. “But most of it occurs in the higher functions: making decisions, reacting quickly, checking checklists and communicating well with other members of the team.”

Fatigue strikes at the heart of some of the most important aspects of a technician’s job. This is why it has been pinpointed as one of the “dirty dozen” root causes of errors in aviation maintenance.


Early shifts that require technicians to rise at 4 or 5 a.m. work against the body’s natural circadian rhythms and can produce fatigue. Hours of wakefulness are an issue as well; once we reach 17-18 hr. of being awake, performance degrades. Unplanned variation in the work schedule—such as working longer hours than planned for an urgent job—make it tougher to get the required rest. And a complex workload can bring about fatigue more quickly than low-intensity tasks. 

Echoing the sleep study above, Gregory adds, “Fatigue doesn’t get us in one fell swoop, like pulling an all-nighter. It’s losing an hour to 90 min. a night. It accumulates and comes on gradually” As a result, “there is a misperception of our ability to adapt to it.” Even when we feel tired, we are usually reluctant to admit it. “We tend to think, ‘I’m a dedicated professional; I’m going to get the job done.’ There’s also a perception that it is weak to say you are tired and need to step aside,” says Gregory.

Technicians and managers must better understand what fatigue is, how it affects us and what its symptoms are. Self-assessments can help diagnose fatigue (see sidebar). Short breaks from a task, walking around for exercise, moving into a well-lit area and caffeine can help combat it.

Gregory urges organizations to adopt a Fatigue Risk Management System (FRMS), to include policies that allow workers to ask for help without being penalized and a system for reporting and analyzing fatigue issues. For instance, if a technician reported working four nights in a row and the fourth night was too much—and there were multiple reports like this over time—it might make sense to reorganize the schedule or pair the worker with a buddy on the fourth night or lighten the workload.

Admittedly, this is difficult and will likely require a massive cultural shift. But it is crucial the maintenance industry move in this direction. “There are reasons we are fatigued,” Gregory concludes. “Everyone has a limit, and at some point people need to recognize that.” 

A version of this article appears in the November 3/10 issue of Aviation Week & Space Technology.

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