Definition
The lingering physiological aftereffects of alcohol consumption that continue to impair a pilot's vision, judgment, balance, and reaction time even after the alcohol itself is no longer detectable in the bloodstream. These effects are particularly damaging to night vision, because the eyes' ability to adapt to darkness and discriminate detail in low light is reduced for many hours after drinking has stopped.
Plain English
The leftover damage to your body and senses after drinking, which keeps affecting how well you can see and think long after you feel sober. At night, this is especially serious because your eyes need to be at their best to see properly in the dark.
Context Anchor
Seen in night flying and pilot health discussions, especially when deciding whether alcohol use from earlier could still affect a flight.
Derivation
Hangover' comes from the idea of something 'hanging over' from the night before -- the effects remain even though the cause is gone. The aviation use simply applies this everyday word to the medical aftereffects that a pilot carries into the cockpit.
Why Pilots Care
These effects measurably reduce visual acuity and dark adaptation, raising the risk of night-flight incidents long after the pilot believes they have recovered.
Grounding Statement
A pilot who drank the night before may feel legal and awake, but still see dim lights less clearly and react more slowly during a night flight.
Intuition Check
Hangover effects do not mean only a headache or upset stomach. In this context, they also mean reduced flying performance that may remain after the pilot feels sober.
Example Sentence 1
The instructor cancelled the night cross-country, explaining that hangover effects from the previous evening could still degrade the student's ability to see other traffic and read the instruments.
Example Sentence 2
Even two days after drinking, hangover effects can slow dark adaptation during preflight checks at dusk.