elevator illusion

elevator illusion

elevator illusionclick for a larger image
An abrupt upward vertical acceleration, usually by an updraft (as can occur in a helicopter), can shift vision downward (the visual scene moves upward) by excessively stimulating the sensory organs. In gravity and linear acceleration, this can create the illusion of being in a climb. The disoriented pilot may push the aircraft into nose-low attitude. An abrupt downward vertical acceleration, usually by a downdraft, has the opposite effect, with the disoriented pilot pulling the aircraft into a nose-up, or climb, attitude. The illusion is likely to occur only if outside visual clues are absent, such as on a dark night or in clouds; and the pilot is either not scanning the aircraft's instruments or does not have faith in them.