Definition
A disorienting physiological reaction caused by exposure to flashing light at frequencies roughly between 4 and 20 cycles per second. In aircraft, it is most often produced by sunlight passing through a slowly turning propeller, a strobe reflecting off cloud or haze, or rotating beacon light entering the cockpit. Symptoms can include dizziness, nausea, confusion, headache, and in rare cases seizure-like reactions.
Plain English
A dizzy, queasy, or disoriented feeling brought on by a fast flickering light in the cockpit, such as sunlight chopped up by a spinning propeller.
Context Anchor
Seen in aviation human factors discussions, especially when flying toward a low sun or when flashing light passes through a propeller or rotor.
Derivation
From flicker (a rapid, repeated wavering of light) and vertigo (from Latin vertere, 'to turn'), originally meaning a sensation of spinning. Together the term names a spinning or disoriented feeling triggered specifically by flickering light.
Why Pilots Care
It can trigger sudden disorientation that leads to incorrect control inputs and loss of aircraft control.
Grounding Statement
Picture flying toward a low sun while the propeller chops the sunlight into fast flashes across your eyes.
Intuition Check
Flicker vertigo is not just annoying glare or ordinary motion sickness. The repeated flashing itself can trigger real physical symptoms.
Example Sentence 1
Flying west into a low sun, the pilot noticed the propeller was creating a strong flicker on the panel and adjusted RPM slightly to break up the flicker vertigo effect.
Example Sentence 2
Changing heading slightly reduced the flicker rate and eliminated the vertigo symptoms.