The Effects of Alcohol and Drugs on Pilot Performance
Acknowledgements: Skybrary
Introduction
From the initiation of the pre-flight process through the securing of the aircraft at the end of the flight, there are many decisions to be made and actions to be taken, from weather interpretation, fuel uplift and route of flight, to the operation of the aircraft and its systems and the navigational aspects of the flight.
Proper procedures must be observed and executed to enable the safe completion of the flight, and to ensure that no hazard is created to either the aircraft or to others in its proximity. Obviously, anything that impairs a pilot's ability to make decisions or execute the associated tasks will increase the potential for an accident or incident.
Discussion
The impairment resulting from the use of some prescription and non-prescription drugs, and of alcohol, is well documented. The negative effects of all these can be exacerbated by the environmental factors of altitude and low humidity found in an aircraft, and be further affected by irregular food intake, fatigue or lack of exercise. Their effects on pilot performance can be quite profound. The effects of some drugs and of alcohol are as follows.
Drugs:
Drugs, and the condition or illness for which they are being taken, can negatively impact on pilot performance, and therefore can pose a significant risk to the safety of flight. Both prescription and non-prescription drugs can impair judgement and degrade coordination.
Common side effects of many non-prescription drugs, such as cold tablets, cough mixtures, antihistamines, appetite suppressors and laxatives, include drowsiness, confusion, blurred vision and dizziness. The effects of some of these drugs can be even more pronounced at altitude than they are on the ground. Drugs can also have a cumulative effect and, if more than one drug is taken at the same time, the combined negative effect may be considerably greater than that of the individual drugs.
Likewise, prescription drugs such as antibiotics or antidepressants can have a pronounced effect on judgement, mental acuity and coordination. The advice of a qualified aviation medical practitioner should be sought to ensure that it is safe to fly during the course of a prescribed drug regimen.
· Antihistamines: These are often taken to reduce the effects of an allergy or for a specific allergic reaction. They cause a level of sedation, dependent upon both the drug and the individual, of drowsiness, degraded reaction time and disturbances of equilibrium and balance.
· Sulphonamides: These “Sulfa” drugs are antimicrobial drugs which inhibit the growth of bacteria. They also cause an allergic reaction in a significant percentage of the population. Side effects of these drugs also can include visual disturbances, dizziness, impaired reaction time, and depression.
· Tranquilisers: These affect reaction time, cause drowsiness, reduced concentration and division of attention.
· Motion Sickness Medications: These, in both oral and topical format, can cause drowsiness and depress brain function. They can also result in temporary deterioration in judgement and in decision making skills.
· Weight Loss Drugs: Appetite suppressing drugs inclusive of amphetamines can cause feelings of well-being that can affect judgment.
· Barbiturates: These, including phenobarbital, can noticeably reduce alertness.
Obviously, the use of any illicit drug is completely incompatible with flight safety!
Alcohol:
Alcohol is very rapidly absorbed into the blood and tissues of the body, and whilst its impairing effects are apparent quite soon after ingestion, it takes hours for these effects to wear off. Nothing, inclusive of sleep, coffee or exercise, will speed up this process, or minimise the effects. Hence the commonly quoted mantra “8 hours bottle to throttle”!
Alcohol is also absorbed into the fluid of the inner ear and will stay there after it has been eliminated from the blood, brain and body tissues. Since the inner ear affects balance, the presence of alcohol in it can lead to spatial disorientation and a potential for vertigo.
Alcohol interferes with the normal absorption of oxygen by the tissues and can result in histoxic hypoxia. As the reduced cabin pressure at altitude will already have reduced the ability of haemoglobin to absorb oxygen, the effect of alcohol in the blood during flight becomes much more pronounced than it would be at sea level. The negative effects of one drink can be magnified as much as 2 to 3 times due to the cumulative effects of alcohol and altitude.
FLY SAFE!