Definition
A reduction in a pilot's mental or physical performance caused by insufficient rest, prolonged workload, stress, disrupted sleep patterns, or extended duty periods, resulting in slower reaction times, impaired judgment, reduced situational awareness, and increased likelihood of error.
Plain English
Being tired enough that your flying suffers — you think slower, miss things, and make mistakes you wouldn't normally make.
Context Anchor
Seen in discussions of aircraft balance, stability, trim, and control forces, especially when an airplane requires constant pressure on the controls to stay where the pilot wants it.
Derivation
Fatigue comes from the Latin fatigare, meaning 'to weary' or 'to tire out.' It refers to the worn-down state that builds up from effort, lack of sleep, or stress — not just feeling sleepy in the moment.
Why Pilots Care
Fatigue increases the likelihood of errors during critical phases of flight and can lead to loss of control or poor decisions.
Grounding Statement
If a pilot has to keep pushing or pulling on the controls just to hold normal flight, that steady effort can wear the pilot down over time.
Intuition Check
Pilot fatigue does not only mean being sleepy. In aviation, it can also mean being physically or mentally worn down by workload, stress, or constant control effort.
Example Sentence 1
After a long day of travel and only four hours of sleep, the pilot recognized signs of fatigue and postponed the flight until the next morning.
Example Sentence 2
Cumulative duty time limits exist to keep pilot fatigue from degrading performance on successive flights.