VFR · Lesson 63 · 8 min · ACS PA.I.H
Personal Fitness to Fly: Alcohol, Drugs, Fatigue and IMSAFE
Summary
Respect the alcohol and drug limits (8 hours, 0.04 percent, no impairing drugs), guard against fatigue and dehydration, and run IMSAFE before each flight to confirm you are fit to fly today.
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Alcohol, drugs, and the 8-hour rule · Topic mastery: Not started
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Under the regulations, a pilot may not act as a crewmember within how long after consuming alcohol?
Why this matters in flight
A perfectly airworthy airplane is unsafe with an unfit pilot. Alcohol, medication, fatigue, and dehydration quietly erode the judgment you rely on, which is why the regulations and the IMSAFE checklist force an honest self-assessment before every flight.
The regulations set clear limits on alcohol and drugs: a pilot may not act as a crewmember within 8 hours of drinking ("8 hours bottle to throttle"), while under the influence, with a blood alcohol concentration of 0.04 percent or greater, or while using any drug that affects safety. Alcohol is doubly dangerous because it also causes histotoxic hypoxia, and its impairment worsens at altitude. Fatigue — whether acute from one long, stressful day or chronic from accumulated poor rest — dulls attention, judgment, and reaction time, and dehydration and heat stress add headache and impaired concentration on top. Rest, water, and food are the simple defenses. To pull all of this together, pilots run the IMSAFE checklist before flight — Illness, Medication, Stress, Alcohol, Fatigue, and Emotion — and decline to fly whenever any item makes the flight unsafe. IMSAFE complements the medical certificate by checking readiness on the specific day, not just once every few years.
Key terms
- 8-hour rule
- "Bottle to throttle": no crew duty within 8 hours of consuming alcohol.
- 0.04 percent BAC
- The blood alcohol concentration at or above which crew duty is prohibited.
- IMSAFE
- Illness, Medication, Stress, Alcohol, Fatigue, Emotion — a preflight fitness self-check.
- Histotoxic hypoxia
- Oxygen deficiency at the cellular level, such as that caused by alcohol.
Sources & references · 4 · 4 linked
Every claim traces to a source — paraphrased knowledge elements pointing at the governing FAA publication. Items marked verified have been checked against the retrieved source text; the rest are pending verification. Where the exact page or regulation has been located in a retrieved document, the source links straight to it.
- 14 CFR 91.17 — 14 CFR Part 91 — General Operating and Flight Rules verified14 CFR 91.17
- PHAK Ch. 17 / hypoxia — Pilot’s Handbook of Aeronautical Knowledge verifiedPHAK Ch. 17 (p. 423)
- PHAK Ch. 17 / fatigue and dehydration — Pilot’s Handbook of Aeronautical Knowledge verifiedPHAK Ch. 17 (p. 423)
- PHAK Ch. 2 / IMSAFE checklist — Pilot’s Handbook of Aeronautical Knowledge verifiedPHAK Ch. 2 (p. 40)
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