Definition
A temporary loss of vision and consciousness caused by reduced blood flow to the brain and eyes during high positive G-loading, when centrifugal force pulls blood away from the head toward the lower body.
Plain English
When a pilot pulls hard in a maneuver, gravity-like forces drain blood from the head. Vision fades to grey, then black, and the pilot can lose consciousness if the loading continues.
Context Anchor
Encountered in discussions of high-performance flight, aerobatics, abrupt pull-ups, and other maneuvers that can place strong force on the pilot’s body.
Derivation
From the everyday sense of 'blackout' meaning a sudden loss of light or awareness. In aviation it specifically describes the visual field going dark as blood drains from the eyes under positive G.
Why Pilots Care
Blackout is an early warning of possible G-induced loss of consciousness, which can result in loss of aircraft control.
Grounding Statement
Picture a hard pull-up pressing the pilot down into the seat while blood has trouble reaching the eyes and brain.
Intuition Check
Blackout does not mean an electrical failure here. In this aviation use, it means the pilot’s vision goes dark because blood is being pulled away from the head during high positive G.
Example Sentence 1
The student eased off the back pressure when his vision started to grey, avoiding a full blackout in the steep pull-up.
Example Sentence 2
Proper anti-G straining maneuvers help delay the onset of blackout in sustained turns.