Instrument Flying Handbook Menu>Human Factors>Illusions Leading to Spatial Disorientation>Coriolis Illusion

The pilot has been in a turn long enough for the fluid in the ear canal to move at the same speed as the canal. A movement of the head in a different plane, such as looking at something in a different part of the cockpit, may set the fluid moving thereby creating the strong illusion of turning or accelerating on an entirely different axis. This is called Coriolis illusion. This action causes the pilot to think the aircraft is doing a maneuver that it is not. The disoriented pilot may maneuver the aircraft into a dangerous attitude in an attempt to correct the aircraft’s perceived attitude.

For this reason, it is important that pilots develop an instrument cross-check or scan that involves minimal head movement. Take care when retrieving charts and other objects in the cockpit—if you drop something, retrieve it with minimal head movement and be alert for the Coriolis illusion.