Alcohol and flying

[Genghis the Engineer]

Over on the rotorheads forum there has been a recent discussion about the legality and practicality of drinking and flying. This got me interested in the real effects (rather than the simplified version in most pilots textbooks) and I went and did some homework in the Royal Aeronautical Society Library. I came up with the following which might interest people in here also...




The basic unit of alcohol within the body is mg/100ml of blood (referred to as %mg BAL). Obviously the relationship between how much you drink and BAL is dependent upon sex, weight, and a few other things. But the references seem to pretty much agree on the following rules of thumb for a standard adult:-

1 pint beer: 24%mg within an hour (can be up to 35%mg, depending upon strength of beer which clearly varies)
1 measure spirits: 12%mg within an hour
1 small glass wine: 15%mg within an hour.

The body (liver) then evacuates alcohol at a pretty constant rate of 15%mg per hour - although the references do admit that depending upon physiology it can actually be anywhere between 8 and 25 %mg/hour.


That stuff most of us had some idea about, but certainly it helps work out where we are after a good night out.


Now to the interesting bit - what the various studies gave as effects of alcohol. The various reports, papers and medical textbooks were pretty consistent. From them I came up with the following:-

11%mg - Reduced ability to maintain correct airspeed or flightpath under high workload

15%mg - 1/3 of pilots in fatal accidents had this level or above in their bodies (from autopsy reports)

20%mg - UK legal flying limit. Significant increase in errors on RT, planning and correct following of procedures.

40%mg - US legal flying limit. Major effect on number of errors on RT and following procedures.

50%mg - Impaired ability to visually fix or track objects

60%mg - Consistent degredation of long term performance even on low workload tasks.

80%mg - UK legal driving limit

150%mg - loss of self control (exactly what is meant by this wasn't defined)

200%mg - double vision, some loss of memory

400%mg - Loss of consciousness.


Three other notes were interesting...

(1) from a study where they tanked pilots up to 150%mg which was that afterwards when BAL had gone down to zero, visual impairment and disorientation could occur up to 7 hours afterwards.

(2) All the studies agreed that under high workload alcohol degraded pilots' performance much more than under low workload.

(3) Up until very high alcohol levels, virtually all the degredation was of judgment or ability to follow procedure, rather than of actual physical skills.

G

[QDMQDMQDM]

Interesting, Genghis, but no revelation. Flying is far more complex a task than driving, requiring a much higher standard of visuospatial coordination, data processing and decision-making ability. You can easily make a convincing argument that any amount of alcohol and driving don't mix, so it's clear that any amount of alcohol and flying do not mix.

I mean, turn it round: what are the arguments IN FAVOUR of drinking and flying?

QDM

[bluskis]

Following the arrest of the BA pilot in Sweden, where the drinking laws even for walking are much more draconian than elsewhere in Europe, I think Genghis may have cottoned on to the importance of pilots knowing when they will be fit to fly following the consumption of alcohol.

The rules of thumb we all know so well may not actually be safe from the legal point of view.

Some European countries driving authorities advise 2 hours per unit for dissipation, so 8 hours would only just dissipate 4 units, or two pints of southern bitter to arrive at the level required for piloting.

Taking the figure of 15 for a small wine, and the worst case for dissipation in Genghis figures, this is in agreement.

[Genghis the Engineer]

I wasn't for a moment questioning whether drinking and flying is a bad thing, of-course it is. What I was endeavouring to find out is how bad, and for how long, which I didn't feel I knew adequately.

G

[QDMQDMQDM]

Rates of elimination of alcohol will vary between individuals, depend on the amount of food in the stomach and no doubt other things too. If an airline pilot on tour is having to do mental arithmetic to figure out whether they'll be fit to fly at 6 am the next morning then ergo they are drinking too much. Forget the maths, I can't see how you can justify drinking more than one unit the night before flying. Quite apart from anything else, flying with a hangover isn't to be recommended either.

QDM

[the wizard of auz]

I believe in the northern territory we work on eight feet from bottle to throttle. ;)

[distaff_beancounter]

One thing that concerns me, in respect of both drivers & pilots, is the use of so-called recreational drugs.

Am I correct in assuming that these can degrade performance, as much as alcohol?

Also, has as much scientific research been done on the effect of drugs on driving/flying, as there has for drink?

[stiknruda]

In the pub on Monday night, I was chatting about flying with an airline pilot mate who thankfully still keeps his hand in by flying the real thing, too (small biplane designed by Curtis somebody!):)

We both agreed that alcohol the previous day (and we're talking 2 maybe 3 pints - not an eyeball bleeding hangover) seriously impairs our ability to handle the G that even relatively gentle aerobatics produces. :-< Twopints and twenty hours later quite fit to fly but aeros whilst they do not make me puke certainly tire me and a normal practice session of say 25 mins hard flying would be impossible.

I really enjoy the odd pint or glass or two of Bordeaux but seriously restrict my intake during the summer aeros competition season. I envy my fellow competitors who retire to the bar as soon as the aeroplanes are put away!

Stik

[englishal]

My advice is to always keep the crate of beer on the back right seat. That way you can still hold on to the stick with one hand while reaching for another cold one :p [this is especially important in hard IMC:o ]

EA

[Flyin'Dutch']

One could argue that anyone who has difficulty in judging in how much they can drink before they fly (both in quantity and time) has got an impaired judgement and should have a hard think about their ability to fly.

After all most flying accidents are not the result of people not being able to do the physical thing but from a mistake in judgement.

It is not just the alcohol which has to be taken into account. When alcohol gets broken down by the body a number of byproducts get produced which not only can contribute to the impairment of the airman/women but also give other side-effects. Furhthermore alcohol works as a diuretic (removes water from your circulation) which contributes to the dry feeling after a night no the razzle. Dehydration in itself gives symptoms (headaches etc) and causes lack in performance.

Alcohol concentration depends on intake and elimination and surprisingly may be gender. Blokes are better in this respect as pound for pound they have a lesser bodyfat percentage than wimmin. Elimination rates of alcohol depend on a great number of factors constitution and ability of your liver to cope with the stuff (which is partially genetically determined) Further liver enzymes can be induced by previous alcohol exposure and the bloodflow through the liver increases by 50% by lying down.

Drinking coffee does not help in reducing the chance of having a hangover as it does not rehydrate you. In fact the caffeine is a further diuretic which will only make matters worse.

It is boring but the best way to cure a hangover is by not drinking too much in the first place.

Flying ability does not just get impaired by alcohol. Other drugs (recreational and prescribed) are equally responsible for a reduction in ability. The fact that the vociferous argue the contrary is proof that they do affect one thing in particular, self judgement! :eek:

Have fun

FD

[Genghis the Engineer]

In fact one of the many papers I found in the RAeS library was a study of just that. Unsurprisingly it was proved that the more somebody had drunk, the more optimistic was their judgement of how long it would be before they would be safe to fly. This also varied greatly with class of pilot. PPLs were the worst, air-taxi and corporate pilots were the best, and airline pilots in the middle (with long haul pilots being better at this judgement than shorthaul). I didn't note the exact figures, but the differences were quite large.

G

[QDMQDMQDM]

It is boring but the best way to cure a hangover is by not drinking too much in the first place.

Actually, the best way to cure a hangover is the hair of the dog that bit you. Hangovers are caused by the liver enzyme alcohol dehydrogenase metabolising the small amount of impurities within any alcoholic drink such as methanol into toxic metabolites such as formaldehyde. Ethanol itself has a much higher affinity for the enzyme and gets metabolised more quickly. Thus, drinking a small amount of alcohol again in the morning slows down the metabolism of the impurities and stops you feeling so lousy. That's the theory anyway.

QDM

[ratsarrse]

With your numbers and a hanful of assumptions, we can conclude then that you can drink 2 pints of average beer and be safe to drive legally immediately and legally fit to fly after 2 hours. I think I might leave it a bit longer for both activities myself.
The difficult thing to judge is the morning after a few beers. Especially when you can't quite remember how many you drank or quite how you got home. 8 pints with chasers equates to an 18 hour recovery period!:eek:

[bluskis]

Ratarsed

I have posted a different handful of assumptions near the start of the thread which indicate you would well be advised to wait a little longer.

[englishal]

Here's a cure or rather a way not to get a hangover which I swear by....

Take 100mg Vitamin B1 tablets before you go on the raz (7000% RDA), available from any good health food shop. Take another before you go to bed.

Apparently the toxic metabolites in the liver bond to the B1 which is water soluble and is then fushed out of the system.

I guess Marmite would do too :O

Cheers
EA:D

[bookworm]

All good stuff.

20%mg - UK legal flying limit. Significant increase in errors on RT, planning and correct following of procedures.


Is that now the case? The ANO 2000 mentions no explicit limit. When was that introduced?

[Genghis the Engineer]

The reports in the library said that it was being proposed as a change to UK law in 1998.

Doing a quick search I found...

http://www.ias.org.uk/factsheets/alcohollaw.pdf

Which on the last page gives 20%mg, but is not clear on whether it is current law, or an intended change. It does look that if it is current law, it may be in the Civil Aviation Act, rather than the ANO.

G

[Stampe]

At present not embodied in Uk law a bill called the Transport (And Shipping I think) Act is about to go through Parliament.That will bring in a 0.02 pro mille limit.Not sure if this will apply to amateur pilots!!?.I asked a CAA AME a few days ago if it would be possible for a teetotaller to fail a breath test at the new low level and he assured me under certain circumstances given the natural presence of alcolhol in the body and the ability of certain foodstuffs to present as alcohol it would be.So be careful out there guys the potential for serious miscarriage of justice is enormous!!.This ridiculously low level has nothing to do with flight safety, no doubt the pious will shout loud to the opposite lets hope its them that get wrongly accused.:rolleyes: