Crew Resource Management
FATIGUE
Fatigue in aviation is recognized as a serious safety concern. Fatigue poses a threat to the principles of CRM and induces human error. Human error is a contributing factor in 80% of all aviation accidents.
The NASA-Ames Fatigue Countermeasures Program has been conducting studies on pilot fatigue for the last 10 years. Their research can be confirmed by interviewing any pilot that has ever flown fatigued.
The Danger of Fatigue
Pilots may be of the opinion that because they can stay awake for extended periods of time, they escape the adverse effects of fatigue. This is not the case. Fatigue is insidious; individuals cannot readily feel the onset of fatigue. The fatigued person may not be aware of it's gradual and cumulative effects and consequently, may be unaware that their performance has become degraded. The fatigued pilot may not easily accept an assessment of their degraded performance or be able to improve their performance despite increased effort.
Fatigued pilots are less vigilant, more willing to accept below par performance, and show signs of poor judgment. They may find it increasingly difficult to make decisions; they may have to recheck information several times as a result of an impaired memory or inability to process information. Alertness and reactions times are decreased. Irritability and mood swings easily block communication and hamper CRM principles.
One of the worst dangers of pilot fatigue is apathy. The fatigued pilot can be indifferent as to the outcome of the flight and their operational performance.
The NASA-Ames studies show that a person who goes without sleep for 18 - 20 hours experiences the same effects as if they had had two or three beers. They are euphoric, punchy, display decreased response time and motor control skills, segmented from their surroundings, impaired thinking.
Causes of Pilot Fatigue
The main causes of pilot fatigue are
- The disturbance of circadian rhythms
- Continuous wakefulness
- Cumulative sleep loss
Circadian Rhythms
The aviation industry maintains a schedule that is 24 hours a day, 7 days a week. Humans operate on a different schedule, a circadian rhythm, which can conflict with a crew member's required work periods. This clash of schedules can affect pilot performance, behaviour and attitude. There are two circadian low periods where an individual will experience increased sleepiness - between 3 and 5 o'clock both a.m. And p.m. A combination of the circadian low period and fatigue could reduce pilot performance by up to 35%.
During sleep, the body's core temperature, often used as a biological marker, drops markedly. If you are forced to stay awake during the time normally allotted for sleep, the disruption of the circadian cycle produces the effects of fatigue.
The more time zones that are crossed, the longer it will take an individual to adjust. It is easier to adjust to a westbound time zone change than eastbound.
Sleep Loss and Microsleeps
The loss of as little as one hour sleep begins a person's sleep debt. Eight hours of disrupted sleep can also produce the effect of too little sleep. You cannot indefinitely deny your body of its required sleep, nor can you substitute it with anything else. The only cure for a sleep debt is to sleep.
Acute fatigue is severe, and could result from the loss of a night's sleep. Chronic fatigue is the result long term sleep debt. It is usually not recognized by the individual and is more difficult to counteract. Acute or chronic fatigue can lead to a microsleep.
Microsleeps are uncontrolled spontaneous episodes of sleep that could last for seconds or minutes. During a microsleep, a person disengages from reality and becomes unresponsive. They fail to respond to outside information.
- There is a 10 times increase of a microsleep at night than during the day
- There is a 10 times increase of a microsleep relative to each hour worked
- Microsleeps increase with cumulative sleep debt
- A microsleep does not decrease a sleep debt
Other Fatigue Inducers
There are other factors that can cause or contribute to pilot fatigue
- Length of duty day
- Time of day, shift irregularities
- Schedule, consecutive duty days
- Multiple layovers in quick succession
- Restricted time available for sleep
- Quality of sleep
- 24-hour layovers following a night arrival
- Easterly direction flights traversing several time zones
- Poor cockpit seat design or ergonomics
- Stressors such as noise, vibration, flicker, heat/cold, wearing headsets
- Accumulation of operational factors such as bad weather, congested airspace
- Boredom, waiting, monotony, monitoring instruments
- Poor diet, hypoglycemia
- Skill fatigue - a progressive loss of performance ability due to prolonged or extreme mental or physical activity
- Vision fatigue - the eye's inability to maintain effective functioning from prolonged visual exertion
- Illness
- Physical exertion
- Dehydration
- Self-medication
- Caffeine, smoking, alcohol
- Hangover
- Hypoxia, flights with cabin altitude over 5,000 ft
- Unresolved stress
Symptoms of Pilot Fatigue
Be aware that these are some of the symptoms that may affect you, but also watch for them in other crew members
- Slowed reaction time, both physically and mentally
- Increased errors despite increased effort
- Individual's underestimation of their performance degradation
- Performance variability and unpredictability
- Preoccupation with a single task
- Fixation on a single source of information
- Perseverance of an ineffective solution
- Short-term memory loss, such as a frequency change
- Impaired judgment and decision making
- Easily distracted by unimportant items
- Sloppy flying
- Loss of initiative
- Depressed, apathetic, lethargic or moody
- Willingness to accept below standard performance
- Limited situational awareness
- Poor communication skills
Common Misconceptions
A pilot suffering the effects of fatigue will not be able to counteract them by
- Skill
- Increased effort
- Stamina
- Physical conditioning
- Education
- Training
- Experience
- Will
- Professionalism
- Motivation
Alcohol and Fatigue
Alcohol is the most widely used sleep aid, but quantities can interfere with quality of sleep therefore increase sleepiness. Pilots on short haul trips consume three times the amount of alcohol on a layover than they consume at home.
Scheduled rest periods allow for required sleep
It is difficult for the body to quickly adjust to required periods of sleep and alertness. The time allotted for sleep on a layover may not coincide with the flight crew member's circadian rhythm.
Subjective analysis
The individual may have a false sense of confidence about their performance abilities when operating in a fatigued state. It is difficult to reliably estimate your own alertness and performance, especially if the individual has a history of flying fatigued and feels motivated enough to overcome the adverse effects.
Artificial enhancers
Caffeine is the most popular artificial stimulant, and can be useful after waking up. Continued caffeine intake will deter sleep during the time allotted for sleep. Caffeine is also a diuretic and causes dehydration.
Melatonin is a depressant currently being promoted in the United States as a natural hormone which allegedly induces sleep in shift workers or elderly people. Melatonin is not legal in Canada. There are problems with quality control, potency and monitoring of this supplement. The biological effects and the long term use of Melatonin is not known.
Fatigue Countermeasures
Some causes of fatigue are controllable, and pilots should make every effort to avoid flying fatigued when possible.
- Do not begin a flight with a sleep debt, make this a priority over outside activities. NASA studies have shown that an individual who received 8 hours of sleep was better able to carry out pilot duties after being awake for 20 hours, than that of a pilot who received just 6 hours of sleep
- Pre-planning for a known sleep disruption is essential for managing alertness. Develop a regular pre-sleep routine, sleep in a comfortable environment
- Proper diet, physical conditioning, avoiding alcohol and smoking will help the body to stay healthy and be better able to cope with the effects of fatigue. Do not exercise or eat a large meal directly before sleep
- Use caffeine sparingly during flight as it may keep you awake later when you are trying to sleep. Water is favoured to counteract dehydration effects.
- If you wake up spontaneously and cannot go back to sleep within 15 - 20 minutes, or have trouble falling asleep, get up and try again later
- During a layover, get as much sleep as you would normally in a 24-hour period. Trust your own physiology - if you feel sleepy and circumstances permit, sleep
- A 40-minute nap, dubbed the NASA-nap, will help to rejuvenate an individual without them entering into a deep sleep, which is more difficult to wake-up from
Summary
- The only remedy for a sleep debt is to sleep
- No amount of will-power will overcome the effects of fatigue
- Pilots retain a level of control over their fatigue levels
- Fatigued pilots must be aware of the gradual and cumulative effects of fatigue, which degrades their performance
Copyright © 1996-2005 by Neil C. Krey unless otherwise indicated.
Non-commercial reproduction rights granted if the following notice is included:
"Source: Neil Krey's CRM Developers Forum, http://www.crm-devel.org"