Page 22 - Nov 2015 Volume 9, Number 11

Under the
Influence
Unlike many relatively incomprehensible FARs, the one dealing with alcohol use is reasonably clear.
FAR 91.17 prohibits any person from acting or attempting to act as a crewmember of a civil aircraft: 1) Within eight hours after the consumption of any alcoholic beverage; 2) While under the influence of alcohol; 3) While using any drug that affects the person’s facilities in any way contrary to safety; or 4) While having an alcohol concentration of 0.04 or greater in a blood or breath specimen. Alcohol concentration means grams of alcohol per deciliter of blood, or grams of alcohol per 210 liters of breath.
The regulation goes on to describe when you, as an aircraft crewmember, must submit to a blood or breath alcohol test, and that the results of any such tests may be used in any legal proceedings. These include proceedings to evaluate the pilot’s suitability to maintain his or her pilot certificate.
Clearly, the FAA is concerned with the sobriety of pilots, and flying under the influence can lead to direct action regarding your pilot certificate. It is also interested in patterns of alcohol abuse and this is something that is evaluated during your FAA medical examination. In this article, I will discuss how much alcohol is too much according to the FAA standards.
Complying with the eight-hour bottle to throttle rule is easy, but how likely is it that you will meet the 0.04 standard eight hours after your last drink? That depends on two factors; how much alcohol you ingest and how rapidly your body metabolizes alcohol.
In terms of how much you ingest, let’s use the “standard drink” as a baseline. This drink contains 14 grams of pure alcohol. In practice, this translates to
20 • KING AIR MAGAZINE
12 ounces of beer, five ounces of wine or 1.5 ounces of an 80 proof spirit. These standards are somewhat arbitrary and assume beer to be five percent alcohol by volume and wine to be 12 percent. Many modern versions of these beverages have a slightly higher alcohol content.
Ethyl alcohol, the alcohol found in alcoholic beverages, is absorbed into the bloodstream directly from the stomach and small intestine. Absorption occurs fairly rapidly and as a rule of thumb, one standard drink will raise the blood alcohol level by 0.02 percent. This can take as little as 20-40 minutes. Rates of absorption do vary with the weight of the drinker and the amount of food in the stomach. You absorb alcohol faster if your stomach is empty. Blood alcohol concentration can also
by Dr. Jerrold Seckler
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Figure 1: Blood alcohol concrentration (BAC) after the rapid consumption of different amounts of alcohol by eight adult fasting male subjects.
(Adapted from Wilkinson et al., Journal of Pharmacokietics and Biopharmaceuticss5(3):207-224, 1977.)
NOVEMBER 2015
Blood Alcohol Concentration (mg%)