FAA Private Pilot Helicopter (PRH)Human FactorsEasy
A private helicopter pilot is conducting a night flight over an unlit rural area. The pilot is looking for an unlit helipad with only the aid of a landing light. Which visual illusion is the pilot most susceptible to?
- AFlicker vertigo
- BReversible perspective illusion
- CAutokinesis
- DSize-distance illusion
Show answer & explanationAnswer & explanation
Correct answer: D. Size-distance illusion
The size-distance illusion can cause a pilot to misjudge the distance to an object if its size is misperceived. In this scenario, the pilot might see the helipad as further away than it is, leading to an earlier-than-needed descent or an overshoot.
Why the other options are wrong
- A. Flicker vertigo is caused by flickering light at certain frequencies, leading to disorientation or nausea.
- B. Reversible perspective illusion occurs when an object's relative motion is misperceived, such as seeing a light moving toward you when it's moving away.
- C. Autokinesis is the illusion of a stationary light moving when stared at in a dark environment.
Size-Distance Illusion
A visual illusion where a pilot misjudges the distance to an object because its size is incorrectly perceived. This often occurs at night or over featureless terrain.
- Misjudgment of distance based on perceived size.
- Common at night or in low visibility.
- Can lead to errors in approach and landing.
Memory trick: Seeing size wrong makes distance a song (of error).