Sensory Systems and Spatial Disorientation
Domain 4 tests vision, the vestibular system and the illusions that cause spatial disorientation. The exam expects you to recognise the illusion and state the correct response: trust instruments, not sensations.
Vision
- The fovea gives detail and colour but needs light; the periphery detects motion and dim light but poor detail.
- Dark adaptation takes about 30 minutes; avoid bright white light and smoking, which reduce night vision.
Vestibular illusions
- Semicircular canals sense angular acceleration; otolith organs sense linear acceleration and gravity.
- Somatogravic illusion: forward acceleration is felt as pitch-up; the pilot may push forward and descend.
- Somatogyral illusion: in a prolonged constant turn the canals adapt; on rollout the pilot feels a turn the other way.
- The leans: after an abrupt correction, the pilot feels banked when wings are level.
- Coriolis: head movement during a turn causes tumbling sensations.
Worked example
On a dark night with no horizon, a pilot accelerates for takeoff and feels the aircraft pitching up. The correct response is to cross-check the attitude indicator and airspeed; pushing forward to 'correct' the false pitch would lower the nose dangerously. The illusion is somatogravic, caused by linear acceleration stimulating the otoliths.
Traps
Trusting sensations in IMC; assuming peripheral vision is good for detail; treating the leans as a real bank; forgetting the black-hole approach causes a low approach.