The coriolis illusion occurs when a 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  flight deck, may set the fluid moving and create the illusion  of turning or accelerating on an entirely different axis. 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 flight deck—if something is dropped,  retrieve it with minimal head movement and be alert for  the coriolis illusion. As in other illusions, a pilot in a prolonged coordinated,  constant-rate turn, will have the illusion of not turning. During  the recovery to level flight, the pilot experiences the sensation  of turning in the opposite direction. The disoriented pilot may  return the aircraft to its original turn. Because an aircraft tends  to lose altitude in turns unless the pilot compensates for the  loss in lift, the pilot may notice a loss of altitude. The absence  of any sensation of turning creates the illusion of being in a  level descent. The pilot may pull back on the controls in an  attempt to climb or stop the descent. This action tightens the  spiral and increases the loss of altitude; hence, this illusion is  referred to as a graveyard spiral.  [Figure 3-7]  At some point,  this could lead to a loss of control by the pilot. A rapid acceleration, such as experienced during takeoff,  stimulates the otolith organs in the same way as tilting the  head backwards. This action creates the somatogravic illusion  of being in a nose-up attitude, especially in situations without  good visual references. The disoriented pilot may push the  aircraft into a nose-low or dive attitude. A rapid deceleration  by quick reduction of the throttle(s) can have the opposite  effect with the disoriented pilot pulling the aircraft into a  nose-up or stall attitude. An abrupt change from climb to straight-and-level flight can  stimulate the otolith organs enough to create the illusion of  tumbling backwards or inversion illusion. The disoriented  pilot may push the aircraft abruptly into a nose-low attitude,  possibly intensifying this illusion. An abrupt upward vertical acceleration, as can occur in  an updraft, can stimulate the otolith organs to create the  illusion of being in a climb. This is called elevator illusion.  The disoriented pilot may push the aircraft into a nose-low  Coriolis Illusion Graveyard Spiral Somatogravic Illusion Inversion Illusion Elevator Illusion Graveyard spiral  Graveyard spin  Correct path 3-6 Figure 3-7.  Graveyard spiral.