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At Wright-Patterson Air Force Base in Ohio, a study subject is wired for a spin in the Dynamic Environment Simulator, a centrifuge that excels in inducing spatial disorientation. (DEPT OF DEFENSE)

The Disorient Express

Despite the best training and technology, why do pilots still die from not knowing which end is up?



Vertigo: A Primer


Spatial disorientation is classified into three types.

-- Unrecognized spatial disorientation (Type I) refers to situations in which the pilot fails to perceive a change from the desired orientation.

-- Recognized spatial disorientation (Type II) occurs when the pilot realizes there is a conflict between the flight instrument readings and what his body senses is the spatial orientation.

-- Incapacitating spatial disorientation (Type III) refers to situations in which the physical symptoms accompanying disorientation — visual impairment, muscle spasms, nausea, or panic — are severe enough to incapacitate the pilot.

Among the illusions pilots may experience:

The Leans  A somatogyral illusion in which, after a prolonged, gentle turn followed by a sudden return to level flight, a pilot will sense a turn (bank) in the opposite direction. A pilot experiencing the leans may lean in the direction of the original turn in an attempt to regain the perception of the correct vertical posture.

The Coriolis Illusion  A somatogyral illusion in which, while the aircraft is turning, a pilot tilts his head — say, to read a map. When the head is tilted out of the plane of rotation, the pilot will experience a sensation of rolling. Depending on the nature of the turn, the pilot may also experience a sensation that the aircraft is pitching, yawing, or both.

The Graveyard Spiral  Unaware the airplane is banked but sensing the nose drop and a loss in altitude, a pilot may pull back on the yoke to try to regain altitude or slow the rate of descent. The increase in back pressure on the control yoke usually results in a tighter turn and a drop of the nose, causing a further loss of altitude. The sequence may continue until the airplane stalls, breaks apart, or hits the ground.

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