The Human Factor: Deadly Fatigue

It is a well-publicized fact that while only 10 percent of general aviation flights are conducted at night, those flights result in about 50 percent of GA accidents. The many dangers of flying at night have been emphasized: inability to see terrain or weather, decreasing temperatures that can lead to fog, generally worse weather, etc. However, maybe the most important factor has been neglected: fatigue. Like the pilots in the accidents listed above, it is likely that most pilots who are flying at night are at least somewhat fatigued. The pilot of the Cessna T303 had to get up very early that morning after less than his normal amount of sleep for a 5 a.m. departure, and then flew several legs over the course of the next four hours before arriving at the destination at 9 a.m. After a boring day hanging around the FBO waiting for his passengers to return, he departed for the return flight at 7:53 p.m., 15 hours after leaving that morning. He faced another four hours of single-pilot IFR flying at the time of night when he would normally be going to bed, but the airplane crashed only 10 minutes later.

The probable cause listed in the NTSB report was: "The pilot became spatially disoriented and as a result failed to maintain control of the airplane." The NTSB also listed IMC conditions and the fact that the pilot was fatigued as contributing factors. The pilot's fatigue was evident to others. An employee at the FBO noticed that the pilot looked tired. The NTSB report stated that he misread the clearance back to the controller and turned off the assigned heading several times. It is little wonder that a pilot who was so tired he couldn't even hold the assigned heading soon entered a spiraling descent from which he was unable to recover.

Fatigue is not just a problem for general aviation pilots. I have a friend who flew F-16s in Operation Iraqi Freedom. He described yelling at himself to try to stay awake on10-hour flights across the Atlantic and six- to eight-hour combat missions. While there are rules limiting flight hours for Part 135 operators, when the pilot or crew are operating without passengers they are under Part 91, with no such restrictions. Many companies take full advantage of this to extend the flying days (or nights) of their employees.

Scheduled airlines operating under Part 121 also have restrictions limiting flight hours and duty days, and specifying time off between duty days. However, the Colgan accident at Buffalo, New York, demonstrated the weaknesses in these regulations, especially the fact that many crew members commute long distances to work. Although the board did not agree to list fatigue as a factor, Chairman Deborah Hersman issued a five-page statement in which she supported the adoption of the final report but lamented the fact that the other members had not voted to include fatigue as a fifth contributing factor. Hersman felt the fact that the crew did not obtain adequate rest before reporting for duty was clearly a contributing factor, and her five-page statement is an excellent summary of what is currently known about the effects of fatigue on pilots.

She points out that the effects of fatigue — slowed reaction time, diminished vigilance and attention to detail, errors of omission, compromised problem-solving, reduced motivation, decreased vigor for successful completion of required tasks and poor communication — all result in performance deficiencies similar to those present during the Colgan flight. These included the captain's inappropriate response to the activation of the stick shaker and the crew's failure to monitor air speed, adhere to sterile cockpit procedures and adequately monitor the flight.

Hersman quotes studies showing that as little as two hours of sleep loss or staying awake for 16 hours both are the equivalent of 0.05 percent blood alcohol content. This is the same as drinking two to three alcoholic beverages in one hour, and for someone driving a car, it results in 11 times the risk of an accident compared with a sober driver. It is also at or above the legal limit for driving a car in 55 countries. In the first article I wrote for Flying magazine ("Bottle to Throttle," August 1985), I pointed out that the danger of flying after drinking is that someone can get away with it, which can lull that individual into complacency about the dangers of flying under the influence of alcohol. The same is true with fatigue. Many people have experienced the terror of driving late at night and suddenly "waking up" and realizing they had been asleep for a few seconds. Studies have shown that fatigued pilots are doing the same thing, even on final approach. Whether in a car or an airplane, it takes only a micro nap to get into a situation from which recovery is difficult if not impossible, especially when suddenly "coming to" after a micro nap.

In our fast-paced, profit-driven, downsized world, fatigue seems to be a part of life for many people. They start the day with a cup of coffee or tea, and then continue to drink caffeinated beverages throughout the day. The problem is that caffeine can't work forever. Your body needs sleep to the point that extreme lack of sleep is fatal. If you are just a little drowsy after a long flight, a cup of coffee or tea is an excellent way to increase alertness before a difficult approach. However, if you are way behind on your sleep and have been using caffeine just to stay awake for the last several hours, it is very similar to getting behind the power curve in an airplane. More power (that extra cup of coffee) just isn't going to make any difference. You need to get the nose down (get some sleep) to recover to a stable flight (fully alert) condition.

So the only thing that really works is to stay ahead of the fatigue curve. That means ensuring there are enough periods of sleep and rest in your schedule so your body and mind can recover for the next challenge. As the Colgan accident demonstrated, a few naps on a red-eye flight or trying to sleep on a sofa in a busy crew room don't qualify as restful sleep. If you are just a little drowsy, a quick 30-minute power nap is much better than a cup of coffee for restoring alertness, but it can't take the place of a good night's sleep in bed in a quiet room.

I learned this lesson once again last week. I am writing this article in Dhaka, Bangladesh, where I am providing error prevention training to the local flight crews. My schedule had been fairly open before this trip, but then suddenly filled up to the point that I returned from a trip to Denver last Wednesday night and then left the following morning on the 30-hour trip to Dhaka. I got no sleep the night before my departure because I did my laundry and packed for the trip. I was so tired when I got on the airplane in Tucson that I fell asleep as we taxied out, then woke up during the initial climb and realized I didn't have my seat belt on. Even though I slept occasionally during the long trip, I never came close to recovering until I arrived in Dhaka and was finally able to get a full night's sleep in a bed.

There is no way we can ultimately win the fight with fatigue. The longer you stay awake, the more your performance will degrade until your body finally decides it has had enough and simply shuts down. At that point there is nothing you can do to stop it, and you likely will not even be aware of what is happening until you wake up again and discover that you have been asleep. Even though we can't beat fatigue, there are some strategies I will cover next month that we can use to more effectively balance the demands of modern life with our body's need for sleep.