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Flight Performance - Level 3

Human Factors-Section 4


Alcohol, taken even in small amounts; produces a dulling of judgement, comprehension and attention, lessened sense of responsibility, a slowing of reflexes and reduced coordination, decreases in eye efficiency, increased frequency of errors, decrease of memory and reasoning ability, and fatigue.

When a pilot undertakes a flight along a given course from one airport to some landing place, hundreds of decisions must be relating to the operation of the airplane and the navigational aspects of the flight. Proper procedures must be accomplished to effect the safe completion of the flight and to ensure that no hazard is created to other airplanes in nearby airspace. Obviously, anything that impairs the pilots ability to make decisions will increase accident potential.

Alcohol is absorbed very rapidly into the blood and tissues of the body. Its effects on the physiology are apparent quite soon after ingestion and wear off very slowly. In fact, it takes about 3 hours for the effects of 1 ounce of alcohol to wear off. Nothing can speed up this process. Neither coffee nor hard exercises nor sleep will minimize the effects of alcohol.

Scientists have recently discovered that alcohol is absorbed into the fluid of the inner ear and stays there after it has gone from the blood and brain. Since the inner ear monitors; balance, alcohol there can be responsible for incorrect balance information and possibly spatial disorientation.

The presence of alcohol in the blood interferes with the normal use of oxygen by the tissues (histotoxic hypoxia). Because of reduced pressure at high altitudes and the reduced ability of the hemoglobin to absorb oxygen, the effect of alcohol in the blood, during flight at high altitudes, is much more pronounced than at sea level. The effects of one drink are magnified 2 to 3 times over the effects the same drink would have at sea level.

A pilot should never carry a passenger that is under the influence of alcohol. Such a person's judgment is impaired. His reactions during ascent to higher altitudes are unpredictable. He may become belligerent and unmanageable and a serious hazard to the safety of the flight.

The rule for both pilot and passengers in relation to alcohol quite simply should be "No alcohol in the system when you fly". The Air Regulations require that a pilot allow at least 12 hours between the consumption of alcohol and piloting an airplane. In fact, more time is probably necessary. An excellent rule is to allow 24 hours between the last drink and take-off time. The after effects (hangover) of alcohol consumption also affect performance capability, causing headache and impairing emotional stability and judgment.



Drugs, as well as the conditions for which they are taken, can interfere with the efficiency of the pilot and can be extremely dangerous. Even over the counter drugs such as aspirin, antihistamines, cold tablets, nasal decongestants, cough mixtures, laxatives, tranquilizers and appetite suppressors impair the judgment and co-ordination. They are responsible for drowsiness, dizziness, blurred vision, confusion, vertigo and mental depression. The effects of some drugs are even more pronounced at higher altitudes than on the ground. Some over the counter drugs taken in

combination will react with each other resulting in a larger effect than even the sum of their individual effects. Some prescription drugs, such as antibiotics, are equally or more dangerous. Usually, however, a person sick enough to be on antibiotics is too sick to be flying.

Any use of illicit drugs is incompatible with air safety. Even the so-called soft drugs affect performance, mood and health.

Anti-histamines (For allergic disorders). Cause sedation with varying degrees of drowsiness, decreased reaction time, disturbances of equilibrium. Do not pilot an airplane within 24 hours of taking an antihistamine.

Sulfa Drugs. Cause visual disturbances, dizziness, impaired reaction time, depression. Remain off flying for 48 hours.

Tranquilizers. Affect reaction time, concentration and division of attention. U.S. military pilots get grounded for 4 weeks following treatment.

Aspirin. Toxic effects are relatively rare and are almost always associated with large doses. If you take aspirin in small dosage and have had no reactions in the past, it is probably safe to take it and fly.

Motion Sickness Remedies. Cause drowsiness and depress brain function. They cause temporary deterioration of judgment making skills. Do not take either prescribed or over the counter motion sickness remedies. If suffering from airsickness while piloting an aircraft, open up the air vents, loosen the clothing, use supplemental oxygen if available and keep the eyes on a point outside the airplane. Avoid unnecessary head movements.

Reducing Drugs. Amphetamines and other appetite suppressing drugs cause feelings of well being that affect good judgment.

Barbiturates (including Phenobarbital). Noticeably reduce alertness. Do not pilot an airplane within 12 hours of treatment.

Anesthetics. Following local and general dental and other anesthetics, a period of 48 hours should elapse before flying.



Because it takes several weeks for the blood circulation to return to normal after a blood donation, it is recommended that pilots who are actively flying refrain from volunteering as blood donors. If a blood donation has been made, you should consult your doctor before flying again.



Fatigue is one of the most common physiological problems for air crew members; and will adversely affect individuals who are otherwise in good health. Fatigue degrades performance. A tired pilot cannot carry out his tasks as reliably and accurately as he should. He is irritable and less alert, willing to accept lower standards of accuracy and performance.

Fatigue begins when the pilot begins a flight and increases with each hour in the air. As a result, at the time of landing when his reflexes and judgment should be keenest, the pilot is most affected by the cumulative effects of fatigue.

The biggest danger of fatigue is that an individual may not recognize its effects.

The onset of fatigue is accompanied by numerous symptoms: deterioration in timing of movements, irritability and lack of patience, a tendency to lock the attention on individual instruments rather than to see the instrument panel as a whole, a tendency to become forgetful and ignorant of relevant cues, a tendency to over control the airplane, an awareness of physical discomforts, a loss of "seat of the pants" flying ability, a tendency to accept a wider margin of error than normal.

Fatigue is caused by many things: lack of sleep, poor nutrition, stress, prolonged and repeated flights, aircraft noise, eye strain, vibration, wide variations in temperature and humidity, heavy workload and uncomfortable working conditions, boredom, monotony, night flights, frustrations from work and family.

A sound physical condition, a healthy mental attitude. proper diet and adequate rest are a pilot's best weapons in fighting fatigue.



The stresses of flying, or indeed of any activity, consume energy. This energy is derived from oxygen and from blood sugar. The pilot is unwise to fly for too long without eating. His blood sugar will be low, that is, his energy reserve will be low. Reactions will be sluggish and efficiency will be impaired. It is a good precaution to carry a nutritious snack on long flights.

Overeating is equally as unwise as not eating. Drowsiness and excessive gas formation are the result of over indulgence at the dinner table just before a flight.

At altitudes above 5000 feet ASL, the body experiences a higher loss of water through the surface area of the lungs than it does at sea level. This loss occurs because the percentage of water vapor in a given volume of air decreases with altitude. Because this water loss is not accompanied by a loss of salt, as occurs with perspiration, there is no accompanying sensation of thirst. Especially on long flights at higher altitudes, it is advised therefore to have a drink of water every hour or so to replace the loss of body fluids.

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Updated: March 12, 2004