Alcohol can produce subtle effects on the perception and performance abilities of a pilot. There is no known threshold level for these effects.
Alcohol, taken even in small amounts, produces a dulling of judgement which results in:
- Reduction of reaction time
- Lack of accurate flying
- Lack of self criticism
- A decrease in spatial orientation
Alcohol is absorbed very rapidly into the blood and tissues of the body. The body metabolises alcohol at the rate of one unit per hour. Binge drinking increases this time drastically.
Alcohol is also absorbed into the fluid of the inner ear. The fluid metabolises alcohol much slower than the rest of the body causing problems with the vestibular system.
The presence of alcohol in the blood interferes with the normal use of oxygen by the tissues causing histotoxic hypoxia. Because of reduced pressure at high altitudes and the reduced ability of the haemoglobin 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.
Alcohol acts as a depressant and an anaesthetic. Binge drinking the night before flight is dangerous as a pilot will still be acting under the influence of alcohol.
The operator ensures that no person enters an aeroplane when under the influence of alcohol or drugs where the safety of the aeroplane or its occupants is likely to be endangered.
Typical Company OPS states that a pilot shall not:
- Consume alcohol less than 8 hours prior to the specified reporting time for flight duty or the commencement of standby.
- Commence a flight duty period with a blood alcohol level in excess of 0.2 promille.
- Consume alcohol during the flight duty period or whilst on standby.
If large amounts of alcohol are consumed then the period should be increased to over 24 hours.
Recommended Amounts of Alcohol
A unit of alcohol is equivalent to:
- A standard glass of wine
- A single spirit, or
- A ½ pint of beer
Specifically it is defined as 15 ml or 9 grams pure alcohol which is equivalent to a bottle of beer.
The following are the recommended Health Council limits for alcohol:
- Men 21 units per week.
- Women 14 units per week.
If a man's intake is more than 6 units per day/30 units per week, women 4 units per day/20 units per week, then there is a greater than 50% chance of an alcohol related illness.
Blood Alcohol Levels commonly used as guides to impairment:
- 0.05% - exhilaration - loss of inhibitions.
- 0.11% - slurred speech and staggering gait.
- 0.20% - euphoria - marked gait impairment.
- 0.30% - confusion.
- 0.40% - stupor.
- 0.50% - coma.
- 0.60% - respiratory paralysis and death.
Alcoholism is a disease and of the many terms given, the World Health Organisation definition is most accepted.
Alcoholics are those excessive drinkers whose dependence upon alcohol has reached such a degree that it results in noticeable mental disturbance or in an interference with their bodily and mental health, their interpersonal relations, their smooth social and economic functioning, or those who show the signs of such developments.
Physical Problems include:
- Digestive system disorders such as ulcers.
- Inflammation of the pancreas.
- Cirrhosis of the liver.
Alcohol and Sleep
The use of alcohol as a relaxant is widely used by flight crew. The odd social drink will not affect a person's well being. Large amounts of alcohol induce a coma like sleep where both the slow wave and REM sleep are badly affected. Prolonged use of alcohol will induce extreme fatigue because of the lack of proper sleep.