Redout

Redout is a perceptual phenomenon in which the field of vision becomes red-tinted during exposure to extreme accelerations. It occurs when venous pressure in the head and ocular vasculature rises, leading to engorgement of the retinal and conjunctival vessels. It is considered the opposite of blackout, which results from insufficient cerebral blood flow.

Causes: Redout is most often associated with high negative G-forces or head-down orientations during aerobatic maneuvers or rapid deceleration, where blood is driven toward the head. It can also occur during sustained high positive G with particular body attitude or during rapid maneuvering. The underlying mechanism is venous pooling in the head and increased retinal venous pressure.

Symptoms: Vision may take on a reddish tint or red haze, sometimes accompanied by fullness or pressure in the head or eyes, headaches, dizziness, or, in severe cases, transient faintness.

Occurrence: Redout is less common than blackout among pilots but is well documented in aerobatic training, fighter operations, and spaceflight contexts.

Prevention and management: Anti-G suits and proper breathing techniques help maintain cerebral perfusion and reduce risk. Maneuver planning to minimize rapid direction changes, adequate rest, and gradual recovery from negative-G exposures are advised. If redout occurs, pilots are instructed to return to a neutral attitude and simulate normal blood flow; seek medical assessment if recurrent, persistent, or accompanied by neurological symptoms.