FAA Sport Pilot Airplane (SPA)Human Factors and ADMHard
A pilot flying straight and level at night stares fixedly at a single stationary ground light for an extended period. The light appears to begin moving even though the aircraft's heading and attitude have not changed. This phenomenon is best described as which illusion?
- AFalse horizon
- BThe Coriolis illusion
- CElevator illusion
- DAutokinesis
Show answer & explanationAnswer & explanation
Correct answer: D. Autokinesis
Autokinesis occurs when a stationary light is stared at in a dark environment for several seconds, causing it to appear to move due to small involuntary eye movements. This can lead a pilot to misjudge the light as another aircraft or make unnecessary control inputs. Frequent eye movement and cross-checking instruments prevent this illusion.
Why the other options are wrong
- A. False horizon involves misreading sloped terrain or clouds as level, not a fixed light appearing to move.
- B. Coriolis illusion is caused by head movement during a turn, not visual fixation.
- C. Elevator illusion relates to vertical acceleration from up/downdrafts, not visual fixation on lights.
Autokinesis
A visual illusion in which a stationary light stared at in darkness appears to move due to the absence of surrounding visual reference points.
- Occurs after several seconds of fixed staring at a single light
- Can cause a pilot to mistake a ground light for a moving aircraft
- Prevented by continuous eye movement and instrument cross-check
Memory trick: Stare too long, the star seems to dance.