FAA Private Pilot Airplane (PAR)Aeromedical Factors and ADMMedium
A pilot flying straight and level in low-visibility conditions enters a slow, gradual turn without realizing it because the inner ear's motion-sensing organs are no longer signaling the turn. Believing the aircraft is still flying straight and level, the pilot tightens the turn to correct a perceived overbank sensation, resulting in a descending spiral that steepens if uncorrected. Which spatial disorientation illusion does this describe?
- ASomatogravic illusion
- BCoriolis illusion
- CGraveyard spiral
- DThe leans
Show answer & explanationAnswer & explanation
Correct answer: C. Graveyard spiral
The graveyard spiral occurs when a prolonged, gradual turn stops stimulating the vestibular system, causing the pilot to sense straight-and-level flight and inadvertently steepen a turn into a descending spiral while trying to correct a false sensation.
Why the other options are wrong
- A. Somatogravic illusion is caused by rapid acceleration or deceleration being misinterpreted as pitch changes.
- B. Coriolis illusion results from tilting the head during a turn, causing a sensation of rotation in a different axis.
- D. The leans is a false sensation of banking caused by an abrupt return to level flight after a gradual bank, not a spiral descent.
Graveyard Spiral
A spatial disorientation illusion in which a pilot in a prolonged turn perceives level flight, then inadvertently tightens the turn into a steep, descending spiral while trying to level the wings.
- Caused by vestibular system adapting to sustained turns
- Common in IMC without instrument reliance
- Pilot may pull back on yoke, tightening the spiral and losing altitude
Memory trick: Trust instruments, not your inner ear's tricks