The Effects Of Fatigue On Performance And Safety

  • E-Mail this Article
  • View Printable Article
  • Text size:

    • A
    • A
    • A


"My mind clicks on and off. I try letting one eyelid close at a time while I prop the other with my will. But the effect is too much, sleep is winning, my whole body argues dully that nothing, nothing life can attain is quite so desirable as sleep. My mind is losing resolution and control."

Charles Lindbergh about his 1927 transatlantic flight


In mid-November 1998, I found myself trying to fly a Boeing 727 on an NDB approach to Category I ILS minimums at Sea-Tac International with one of its three engines inoperative. My previous flying experience had mostly been flying single-engine Cessnas and Piper Chieftains, yet here I was in a 180,000-pound 727 flying in conditions worse than I had ever seen. I was battling to keep up with the airplane for quite a while and was not being very successful. I landed a half-mile short of the runway and to the right of the centerline. Fortunately, no one was hurt and there was no damage -- except to my pride.

We were in a simulator, of course, and the lesson of the day was about how, in an emergency, a mathematical glideslope may quickly be calculated to turn an NDB approach into a precision approach. It's a lesson that I have quickly erased from the cerebral database; however, I learned a more important lesson that day which has stayed with me ever since: I learned that I am not immune to fatigue.

I had not eaten since noon the day before or slept well that night. I was pretty exhausted just going into the simulator, but after four hours, I was wiped out. I was in no condition to fly in those conditions and my performance proved it.

The next day was checkride day. I made sure that I was well-rested and well-fed. This time I was ready, and this time I did a fantastic job. I kept the needles centered as if they were glued in place. I performed the same approach as the day before and broke out of the clouds right over the approach lights and landed well within the touchdown zone. Without a doubt, being well-rested made all of the difference.

The Accident Record

After that experience, I have been much more aware of my state of alertness and the things that might diminish it. However, many people and organizations either don't seem to take the issue seriously enough or place their own agendas ahead of safety. For example, in order to save the reputations of some airlines and pilots, company doctors often disguise symptoms of fatigue as other illnesses[1]. Also, in 1996, the U.S. Air Transport Association (ATA) voiced opposition to an FAA proposal to set new limits on flight and duty time, reserve duties and crew rest. They said there is no scientific evidence to show fatigue is a factor in safety[2]. This kind of thinking is not only irrational but also dangerous. Only recent events are bringing the importance of recognizing fatigue to the fore.

Many pilots have heard the story of the pilot who fell asleep with his autopilot on and woke up two hours from the nearest land with only one hour of fuel remaining. The story may be just an "airborne legend," dreamed up by a group of hangar-flying buddies after a long day of towing gliders. True or not, no pilot with a modicum of experience can deny having occasionally had to battle a bout of fatigue or that it somehow affected their performance.

There are many documented accidents that can been attributed to pilot fatigue. Most recently would be the June 1999 fatal runway accident of American Airlines Flight 1420 in which a McDonnell Douglas MD-82 overran the end of the runway, went down an embankment, and impacted approach light structures after landing at the Adams Field Airport in Little Rock, Ark.  Thunderstorms and heavy rain were reported in the area at the time of the accident. There were 11 fatalities, including the aircraft captain, and numerous injuries among the 145 passengers and crew aboard the flight. While the final report has not been released, it is expected that fatigue will be listed as a contributing cause.

Although Korean Airline's (KAL) management emphatically denies it, the crash of KAL Flight 801 in Guam on August 6, 1997, was the result of several errors by the crew, most notably a lack of situational awareness resulting in "controlled flight into terrain (CFIT)." However, the pilot in command of the flight, Captain Park Yong-chul, was a senior and experienced pilot in the company. While Captain Park was not familiar with the terrain, and visibility at the time was reduced due to rain, the approach into Guam should not have been difficult. So what caused Captain Park to lose concentration and situational awareness, and thereby fly a perfectly good 747 into a hilltop, killing 227 people? Could it be that prior to flying to Guam he had flown from Seoul to Australia, back to Seoul, to Hong Kong, and then back to Seoul again before his fateful trip to Guam, all with only a few hours of rest?[3] The answer should seem pretty obvious.

The NTSB said that Joe Reid, pilot-in-command of the Cessna 177B Cardinal in which he, seven-year-old Jessica Dubroff and her father were killed, suffered fatigue from the first day's flight. That fatigue seems to have impaired his judgment, allowing him to depart into weather that a United Express Beech 1900 Captain deemed worth a delay.[4]

On August 18, 1993, a Connie Kalitta DC-8 crashed on a 1/4-mile base leg to final. The flight crew had been on duty for 18 hours and flown nine, thereby experiencing sleep loss and a disruption of their circadian rhythms. In his introductory speech at the November 1995 Fatigue Symposium near Washington, D.C., Jim Danaher, chief of the NTSB's Operational Factors Division, commented on the accident by stating, "The company had intended for the crew to ferry the airplane back to Atlanta after the airplane was offloaded in Guantanamo Bay. This would have resulted in a total duty time of 24 hours and 12 hours of flight time…."[5]

Was the crew legal to fly? Unfortunately yes, but doing so proved to be nearly fatal. The NTSB accident report states, "Probable Cause: The impaired judgment, decision-making, and flying abilities of the captain and flightcrew due to the affects of fatigue." While the report goes on to list other causes, it is rare to find fatigue as the primary cause as it does here. Usually, pilot fatigue is relegated to the Additional Factors section of a report. As for the Additional Factors section, the NTSB lays some blame on the FAA for inadequate flight and duty time regulations.[6] One must wonder how a person may be legally rested if they are flying under one part of the Federal Aviation Regulations (FARs), but not legally rested if they are flying under another part. Does it not make sense that if a person is too tired to fly, then the part of the regulations that they are operating under is irrelevant?

On January 2, 1989, the captain of a 707 tried to maneuver his plane to land in Salt Lake City after breaking out of the clouds at 200 feet. He dragged his left, outboard engine on the runway, leaving a 60-foot-long gouge. Within the preceding 30 hours, he had been on duty for 19 hours, and flown 13 hours. He had been off duty for almost 12 hours, but was only able to get one hour of sleep in that time. Pilot fatigue due to disrupted circadian rhythm was cited as a contributing factor.[7]

In August 1985, the crew of a Learjet killed themselves and their passenger in a botched approach to Gulkana, Alaska. One of the contributing factors was that the company would shift the crew's duty/rest requirements from FAR Part 135 to those of FAR Part 121, thereby disrupting their sleep patterns and inducing fatigue.[8]

The problem is not limited to aviation either. In maritime events, fatigue has been cited as contributing to the Exxon Valdez[9] and World Prodigy[10] disasters. It was a factor in the nuclear accidents at Three Mile Island and Bhopal and affected the decision-making process of the doomed space shuttle Challenger mission.[11]

Symptoms...

The list goes on and on. So how do we address the issue? What can be done to rectify the problem? Before we can offer any solutions, we have to identify the problem. Fatigue is closely interrelated to other problems in that it can be a symptom of them, or it can be the cause. The most obvious cause of fatigue would be a lack of sleep, but other factors would include stress, anxiety and poor health. It can also be a cause of these problems. Furthermore, fatigue can be the symptom of other problems such as hypoxia and dehydration.

Symptoms of fatigue include a feeling of indifference to one's performance, increased reaction time, a decreased ability to concentrate on multiple tasks, fixation, short-term memory loss, impaired judgment, impaired decision-making ability, distractibility, sloppy flying skills, reduced visual perception, loss of initiative, personality changes and depression.[12]

Quality Sleep

To understand the problem of inadequate sleep, we should understand what sleep is. There are four stages of sleep starting with about 10 minutes of REM (rapid eye movement) sleep where the mind is active (dreaming) and the smaller muscles twitch. During the next three stages the mind and body slow down. After 45-70 minutes, we return to REM. People go through this cycle several times through the night and an interruption of any stage (i.e., the hotel maid waking you up to see if you need the room cleaned, or a phone call from dispatch to tell you that they have received your fax) will render that whole cycle ineffectual.[12]

One major cause of sleep deprivation is a disruption of our internal light/dark cycle, called circadian rhythms. Circadian rhythms are the biological clock existing in our brains since prehistoric times, which tell us that we should work when it is light (day) and sleep when it is dark (night). The word comes from the Latin "circa" (about), and "dies" (day).[13] Circadian changes make a person try to sleep when their mind is wide-awake, and they force them to remain awake when their mind is screaming to go to bed. Long schedules and changes in circadian rhythms are among the most common causes of fatigue faced by pilots, mainly because there is little that can be done to change them. We are all subject to these factors and the best defense is to limit their effects by controlling the fatiguing factors that we can.

Diet And Nutrition

For example, any pilot from a brand-new student to the about-to-retire captain will tell you that the beverage of choice among pilots is coffee. However, while coffee is a stimulant and causes a temporarily increased level of alertness, fatigue is symptomatic of its withdrawal. Furthermore, coffee is a diuretic, which causes the body to discharge more fluid than it is taking in, resulting in dehydration, which in turn can cause fatigue.

While there can be no argument against being in good physical shape, a strenuous workout can also cause dehydration and should be completed with ample time for rehydration. Also, environmental conditions can cause dehydration. Obviously, the 130-degree ramp at Phoenix is a place where dehydration is of concern, but what about the 72-degree cockpit in which we work? Worry about it, too. The average humidity there is low and can cause a dramatic increase in fluid loss.[12]

Another factor is nutritional intake. The diet of a pilot can at times be horrendous. What can you do when you are sitting in an FBO, ten miles from the nearest restaurant, and have not eaten since 5:00 a.m.? You may have slept well the night before and the flight may have been easy and relaxing; but you are tired and weak and do not know why. You pull out a few bucks and feed them to the vending machine, hoping that it might relinquish its firm grasp on that bag of Ruffles and the Snickers bar. Then you buy a Coke with the change. Very quickly you notice that your energy is returning. Even your mood improves. It turns out that you may have been hypoglycemic; your blood sugar was too low.[12] While the nutritional value of that kind of food is objectionable, it does have a redeeming quality in that it can stave off or reverse the effects of hypoglycemia, which can be a cause of fatigue. It should be noted that a healthy diet is much better in the long term and may be had by packing your own meal, receiving catered meals from the company, or getting a healthy meal at the airport diner.

Illness And Environment

If you're sick, don't fly. It is an obvious statement, but many people fly when they are sick anyway. Many companies make it financially disadvantageous for crew members to report their malady. Some pilots think that they are invincible and that they perform better than most even when afflicted with a cold or flu. Others know that they are impaired by an illness so they compensate with antihistamines. Antihistamines help by alleviating the symptoms of illness but by their nature they also increase fatigue. Regardless, these people are doing their fellow crew members a disfavor by exposing them to their illness and further increasing the possibility of an operational error due to fatigue.[12] They may be involved in an accident, or maybe not, but they can unwittingly be a contributing cause to one.

Other environmental concerns include noise and vibration, hypoxia, extreme temperatures, and flickering light (as in helicopters). Many less-experienced pilots will go out and enjoy an exciting layover at the cost of their vitally required rest. Some companies stretch their employees' rest requirements to the legal limit of flight and duty time restrictions to maximize productivity. Long international flights and automation cause a reduction of mental stimulus and an increase in boredom.

...And Solutions

Fatigue in pilots can be reduced or eliminated with simple and practical steps on the part of the FAA, the airlines and the individual crew members. The FAA's role is to make and enforce laws concerning the conduct of airlines and pilots. These laws should be rewritten to be simple and straightforward, and should not vary by type of operation. The FARs already regulate certain activities which may affect fatigue, such as alcohol and drug use, medical certification requirements, and requirements for the use of oxygen. Why does the FAA not consider circadian rhythm changes in their law making? Why is it that one type of operation has different flight and duty time restrictions than another? Does the type of operation have any bearing on the level of fatigue that crew members experience? Why does the FAA mandate that simple duct tape requires their testing and approval (thus quadrupling the cost) yet companies are allowed to put a flight crew in the noisiest hotels just to save a dime? Why is it not allowed for flight crews to alternate taking controlled, planned naps while en route? The rules are changing, but not fast enough.

The airlines need to recognize that the cost of fatigue and the errors that result are many times higher than the cost of ensuring adequate rest for their crews. Seventy percent of the accidents in aviation are due to pilot error, and fatigue is a major cause of those errors. If the airlines took measures to reduce fatigue, they would reduce the chances of errors due to fatigue. Many airlines have seen their total demise due to a single accident (i.e., Valujet Flight 592). It is obvious that preventing fatigue would have a major cost advantage.

Finally, and arguably most importantly, fatigue can be prevented by individuals taking preemptive measures. Pilots take great pride in their skills and abilities, yet they let their performance degrade needlessly due to fatigue. It is in their hands to take the necessary steps to remain safe and alert, even when the government and their employers are allowing them to work irrational and dangerous schedules. Planning to get enough sleep before a trip is the most obvious step. Using earplugs and eye masks can help in this endeavor. Another step would be to eat properly. Everyone should exercise often, but remember to do so well before the start of a trip. This will make the pilot healthier and more alert. Pilots can stay hydrated by drinking plenty of water, especially during a flight, and avoid coffee, sodas and alcohol. They can wear noise-reducing headsets if the cockpit is loud. Finally, they must stay home when they are ill, for their own sake and for their fellow crew members.

Fatigue is often the cause of pilot error and it is therefore often the vital link in the chain of events leading to an accident. It is often the reason that pilots don't make the right decisions or fly as well as they can. If a reduction in fatigue yielded an increase in pilots' decision-making abilities and performance, then there would obviously be a decrease in pilot error and the accidents that sometimes ensue. Not all errors result in accidents, but if everyone in the airline industry took the appropriate steps to combat fatigue, it is likely that pilot error due to fatigue, therefore accidents due to pilot error, would drop significantly.

-- Mark Brandon Printup


1. Daniel Waddell, Doctors 'help to disguise pilot fatigue', The Daily Telegraph, 17 Sep 1998.
2. Steve Holland, Independent pilots back new FAA fatigue rules, Reuters, 17 Jun 1996.
3. Don Phillips/Washington Post, Crew reportedly didn't know crash imminent: Plane's wheels were in place for Guam Landing, The Dallas Morning News, 8 Aug 1997.
4. National Transportation Safety Board, Aircraft Accident Report: In Flight Loss of Control and Subsequent Collision with Terrain, Cessna 177B, N35207, Cheyenne, Wyoming. 11 Apr 1996. Washington, DC.
5. Duke, Tom "Battling Fatigue-The Challenge is to Manage It" Editorial. NATCA Voice February 1997.
6. National Transportation Safety Board, Aircraft Accident Report: In Flight Loss of Control and Subsequent Collision with Terrain, DC-8-61, N814CK, Guantanamo Bay, Cuba. 18 Aug 1993. Washington, DC.
7. National Transportation Safety Board, Aircraft Accident Report: Uncontrolled Collision with Terrain, Boeing 707-323B, N712PC, Salt Lake City, UT. 22 Jan 1989. Washington, DC.
8. National Transportation Safety Board, Aircraft Accident Report: Improper IFR Procedure, Gates Learjet 24D, N455JA, Gulkana, AK. 20 Aug 1985. Washington, DC.
9. Marine Accident Report-Grounding of the US. Tankship Exxon Valdez on Bligh Reef, Prince William Sound, Near Valdez, Alaska, 24 Mar 1989. Washington, DC: National Transportation Safety Board (NTSB/Mar-90/04); 1990:1-256.
10. Marine Accident Report-Grounding of the Greek Tankship World Prodigy off the Coast of Rhode Island, 23 Jun 1989. Washington, DC: National Transportation Safety Board (NTSB/Mar-90/04); 1990:1-47.
11. Biological Rhythms: Implications for the Worker. Washington, DC: US Congress, Office of Technology Assessment. US Government Printing Office; 1992: 1-249.
12. Reinhart, Richard O. "Basic Flight Physiology." (Blue Ridge Summit: TAB Books, 1992), pp. 177-182.
13. "Learning to Live with Light-Dark Cycles," Vol. 124, USA Today Magazine, 1 Feb 1996.

Bibliography

Tom, Duke "Battling Fatigue-The Challenge is to Manage It." Editorial. NATCA Voice, February 1997.
Steve Holland, "Independent Pilots Back New FAA Fatigue Rules." Reuters, June 17, 1996.
Don Phillips/Washington Post, "Crew Reportedly Didn't Know Crash Imminent: Plane's Wheels Were in Place for Guam Landing." The Dallas Morning News, August 8, 1997.
Reinhart, Richard O. Basic Flight Physiology. Blue Ridge Summit: TAB Books, 1992.
Daniel Waddell, "Doctors Help to Disguise Pilot Fatigue." The Daily Telegraph, September 17 1998.
"Learning to Live with Light-Dark Cycles." Vol. 124, USA Today Magazine, 1 Feb 1996.
Biological Rhythms: Implications for the Worker. Washington, DC: US Congress, Office of Technology Assessment. US Government Printing Office; 1992: 1-249.
Marine Accident Report-Grounding of the Greek Tankship World Prodigy off the Coast of Rhode Island, 23 Jun 1989. Washington, DC: National Transportation Safety Board (NTSB/Mar-90/04); 1990:1-47.
Marine Accident Report-Grounding of the US Tankship Exxon Valdez on Bligh Reef, Prince William Sound, Near Valdez, Alaska, 24 Mar 1989. Washington, DC: National Transportation Safety Board (NTSB/Mar-90/04); 1990:1-256.
National Transportation Safety Board, Aircraft Accident Report: Improper IFR Procedure, Gates Learjet 24D, N455JA, Gulkana, AK. 20 Aug 1985. Washington, DC.
National Transportation Safety Board, Aircraft Accident Report: In Flight Loss of Control and Subsequent Collision with Terrain, Cessna 177B, N35207, Cheyenne, Wyoming. 11 Apr 1996. Washington, DC.
National Transportation Safety Board, Aircraft Accident Report: In Flight Loss of Control and Subsequent Collision with Terrain, DC-8-61, N814CK, Guantanamo Bay, Cuba. 18 Aug 1993. Washington, DC.
National Transportation Safety Board, Aircraft Accident Report: Uncontrolled Collision with Terrain, Boeing 707-323B, N712PC, Salt Lake City, UT. 22 Jan 1989. Washington, DC.