FAA Private Pilot Helicopter (PRH)Human FactorsHard
During takeoff, a helicopter accelerates rapidly and climbs into low clouds with no visible horizon. The pilot experiences a strong sensation of pitching up excessively and instinctively pushes the cyclic forward. What illusion is being experienced?
- ACoriolis illusion
- BThe leans
- CElevator illusion
- DSomatogravic illusion
Show answer & explanationAnswer & explanation
Correct answer: D. Somatogravic illusion
The somatogravic illusion occurs when rapid linear acceleration during takeoff is misinterpreted by the vestibular system as a nose-up pitch attitude, causing the pilot to push the nose down—potentially flying into terrain. This is especially dangerous in helicopters during rapid acceleration in IMC or dark conditions.
Why the other options are wrong
- A. Coriolis illusion results from head movement during a prolonged turn, not linear acceleration.
- B. The leans results from a sudden return to level flight after a gradual, unnoticed bank, not acceleration.
- C. Elevator illusion' is not a recognized standard vestibular illusion in FAA material.
Somatogravic Illusion
A vestibular illusion where rapid acceleration is perceived as a pitch-up attitude, prompting the pilot to push the nose down inappropriately.
- Occurs during rapid acceleration such as takeoff
- Most dangerous at night or in IMC with no visual horizon
- Can lead to controlled flight into terrain if pilot trusts sensation over instruments
Memory trick: 'Speed feels like a climb' — trust the gauges, not your gut.