Alcohol

Alcohol is a major concern for aviation as it can cause serious incidents. Alcohol impairs performance and takes away anxiety and inhibitions (Robson, 2008³). This can be fun in a social context, however can have serious implications if brought onto the flight deck or other safety sensitive roles where good performance is essential (Hawkins, 1993²).

Legalities

Although this list is by no means comprehensive, in most countries it is illegal to:

Fly an aircraft and consume alcohol
Fly with a blood alcohol content (BAC) of more than 40mg/100ml
Fly within 8 hours of consuming alcohol

Prevalence in General Aviation

An early study by Harper and Albers (1964¹) stated that 35.4% of general aviation (GA) pilots involved in fatal accidents showed BACs that were measurable enough to impair performance. However, later studies revealed that this figure could be due to putrefaction (causing higher alcohol levels) as this was not considered during this study (Modell & Mountz, 1990; Cook, 1997). Later studies have more modest revelations of roughly 10 – 30% of GA pilots in fatal crashes showing measurable BACs, only half of which were above legal limits (Modell & Mountz, 1990).

Effects of Alcohol

The table below, adapted out of Campell & Bagshaw (2002) shows the general effects of alcohol at different BACs (by general I am referring to the fact they represent thresholds for everyone, not just pilots).

30mg/100ml	Increases chance of having an accident
50mg/100ml	Impairment of judgement
150mg/100ml	No self-control
200mg/100ml	Double vision accompanied by memory loss
400mg/100ml	Loss of consciousness
Table 1: the general effects of alcohol upon the human body at varying BACs

Based on several studies into the effects of drinking and flying, Cook (1997) compiled a set of piloting tasks that were affected at different BACs:

10-30mg/100ml:

Trouble with terrain separation
Impaired performance during aircraft descent
Impaired performance when turning (angular acceleration)
Impaired performance in dim lighting

30-50mg/100ml:

Worsened impairments of what is in the above category
Inability to manage heavy workloads
Cannot track radio signals properly
Cannot track targets properly
Inability to effectively follow movements instructed by air traffic control
Inability to configure flight controls properly
Inefficient at coordinating the flight (ie navigation, monitoring instruments)
Inability to perceive other traffic, effecting capability of avoiding other aircraft
Inability to respond quick enough to environmental cues such as flight controls (stick and foot pedals)
3 dimensional coordination
Poor short term memory
Slowed reaction times
Impaired performance at higher gravitational forces (5 g)

50-120mg/100ml:

Progressively worsened impairment of everything in the above categories
Impaired oculovestibular functions (poor interaction between vision and balance)
Impaired performance at moderate gravitational forces (3 g)

It is clear from these tables that although we might afford such impairments in the above table when we are on the ground, the impairments caused by alcohol unto flightdeck performance (as shown above) are greater and potentially more catastrophic. The same concept applies to all safety sensitive roles (eg air traffic control).

References

Campbell, R.D. & Bagshaw, M. (2002). Human performance and limitations in aviation (2nd ed.). Oxford, United Kingdom: Blackwell Science. CASA Alcohol and Substances. Retrieved from Youtube on 16 August 2012. Cook, C.C.H. (1997). Alcohol and aviation. Addiction 92(5), 539-555.

1. HARPER CR & WR ALBERS (1964). Alcohol and general aviation accidents. Aerospace Medicine, 1964, volume 35, pages 462-464.

2. HAWKINS Frank H (1993). Human factors in flight (2^nd ed). Ashgate (England, UK), 1993. ISBN 9781857421354.

Modell, J.G., & Mountz, J.M. (1990). Drinking and flying: The problem of alcohol use by pilots. The New England Journal of Medicine, 323(7), 455-461.

3. ROBSON David (2008). Human being pilot: human factors for aviation professionals. Aviation Theory Centre (Cheltenham, Australia), 2008. ISBN 9781921176951 .

Want to know more?

The Effects of Alcohol on the Human Body: For a more in-depth understanding of how alcohol can impair flight performance it is recommended that you go to this link and familiarise yourself with some specific alcohol related conditions that can affect flight safety.