Spatial Disorientation and Illusions
This domain tests spatial disorientation and visual illusions: how the vestibular system misleads pilots, the named illusions, and the countermeasures that prevent loss of control.
Vestibular illusions
- Semicircular canals detect angular acceleration; otolith organs detect linear acceleration and gravity but cannot distinguish the two.
- Somatogravic illusion: acceleration on take-off feels like pitch-up, provoking a forward push on the control column.
- Leans: after rolling level from a sustained turn, the pilot feels a turn in the opposite direction and may re-enter the turn.
- Graveyard spiral: in a prolonged turn the bank increases and the nose drops, but the pilot perceives level flight and may steepen the spiral.
- Coriolis: head movement during a sustained turn causes tumbling sensations.
Visual illusions
- Black-hole approach: sparse ground lighting makes the aircraft seem higher than it is, leading to a low approach.
- False horizon, autokinesis, runway width and slope, and height/distance illusions distort approach judgement.
Countermeasures
- Trust and cross-check instruments; maintain a scan; avoid abrupt head movements; use automation and verbal callouts; brief the approach lighting.
Worked example
After a sustained turn the pilot rolls wings level and feels a turn the other way. The sensation is a lean, produced by canal adaptation. Correct action is to check the attitude indicator and hold level flight; re-entering the turn to correct the false sensation can start a graveyard spiral.
Traps that cost marks
- Trust your body is wrong in IMC; vestibular sensations are unreliable.
- Confusing somatogravic acceleration with a real pitch-up.
- Treating a graveyard spiral as a deliberate manoeuvre rather than a disorientation event.