The deep, dark secret
Fortunately, commercial planes seldom crash, but when they do, pilot error is more likely to be responsible than equipment failure. Shocking though it may be, fatigued pilots make more errors than rested ones. Sorting out the role of fatigue in air crew performance is the job of Ron Simmons, an FAA expert on how human beings perform in the cockpit.

Simmons notes that flying a modern, computerized jet like the Airbus 320 is closer to "systems management" than traditional flying. And system management can be boring when it's going smoothly.

Although only two fatal accidents in civil aviation history have been blamed on fatigue, he says, 60 to 80 percent of accidents are associated with a human mistake, and the National Transportation Safety Board (NTSB) has issued nearly 80 recommendations related to fatigue since 1972 (for all modes of transport -- not just airplanes).

Here's a report of a 1993 plane crash that the NTSB blamed in part on "the impaired judgment, decision-making, and flying abilities of the captain and flightcrew due to the effects of fatigue."

Some accidents that are not blamed on fatigue are pretty suggestive, Simmons argues. Once, a pilot crashed after 16 hours on duty because he read an altimeter (defined) incorrectly. "He had been flying safely for 15 hours, and suddenly he couldn't read an altimeter?" Simmons asks. "I find that hard to believe. That's fatigue."

Fatigue, he says, is a degradation of mental performance that can be caused by a lack of sleep, but it's not the same thing as a lack of sleep, Simmons points out. "Fatigue is a symptom. It's kind of like a fever in that it can have many causes." Some of the causes are not directly related to sleep: illness, the environment, working conditions, circadian rhythms, and workload can all contribute.

Snoozin?
New research techniques are giving insight into the physiological effects of fatigue on the brain. For example, researchers have measured a 20 percent loss in the brain's electrical signals after 20 hours working, indicating a general decline in function.

Simmons adds that positron emission tomography (PET) scans, which show how fast the brain consumes glucose, reveal that the frontal lobes are very active in a rested person, but are quite sluggish after 24 hours of wakefulness. Since the frontal lobes have a role in working (short-term) memory, attention, concentration, reasoning, sensory recognition, and verbal and non-verbal processing, Simmons says it's not surprising that fatigued pilots who know perfectly well how to fly can make mistakes.

Want to take a look at some of the other factors that contribute to fatigue? (Hint: Some of this might interest people who pilot cars, trucks, even desks.)

There are 1 2 3 4 5 6 7 8 9 10 11 12 documents. (Glossary | Bibliography)