Definition
A temporary, partial loss of vision caused by reduced blood flow to the eyes during positive G-loading. Colors fade and peripheral vision narrows, but the pilot remains conscious. Grayout is an early warning sign that further G-loading may lead to blackout or G-induced loss of consciousness (G-LOC).
Plain English
When you pull hard on the controls and the aircraft loads up with Gs, blood drains away from your eyes. Your vision starts to go dim and washed out, like the world is fading to gray. You can still see and fly, but it's a clear signal to ease off before things get worse.
Context Anchor
Seen in discussions of steep turns, aerobatics, high-performance aircraft, and the physical effects of acceleration on pilots.
Derivation
Formed from 'gray' (the color the world appears to take on) and 'out' (as in fading out). The word describes exactly what the pilot experiences: vision draining of color toward gray before potentially going completely dark (blackout).
Why Pilots Care
It is an early warning that consciousness may be lost if G-forces increase or are sustained without corrective action.
Analogy
It is like a room light fading before it goes completely off. The fading is the warning sign; waiting for total darkness means the problem has already gone much farther.
Grounding Statement
During a hard pull-up or steep maneuver, blood can be pulled away from the head, and the pilot’s vision may start to gray out.
Intuition Check
Grayout does not mean the pilot is simply tired or dizzy. It means vision is being affected by reduced blood flow during acceleration.
Example Sentence 1
During the steep pull-up, the pilot felt a grayout coming on and immediately relaxed back-pressure on the stick.
Example Sentence 2
Centrifuge training teaches pilots to recognize the first signs of grayout and apply the anti-G straining maneuver in time.