Definition
A set of recommended pilot practices for recognizing and counteracting visual illusions during the approach and landing phase. The core practices are: anticipate the possibility of visual illusions during approaches to unfamiliar airports, particularly at night or in adverse weather; consult airport diagrams and the Chart Supplement for runway slope, terrain, and lighting information; conduct an aerial visual inspection of unfamiliar airports before landing; use Visual Approach Slope Indicator (VASI) or Precision Approach Path Indicator (PAPI) systems whenever available; cross-check the visual picture against flight instruments such as the altimeter, vertical speed indicator, and glidepath references; avoid relying solely on outside visual cues, especially in conditions known to produce illusions; and remain alert to terrain features and surrounding obstacles during the final approach.
Plain English
Your eyes can fool you on approach, especially at night, in bad weather, or at unfamiliar airports. To stay safe, plan ahead, study the airport before you arrive, use the runway's visual glidepath lights when they're available, and cross-check what you see outside against your instruments instead of trusting your eyes alone.
Context Anchor
Encountered during landing training, especially at night, at unfamiliar airports, in rain or haze, over featureless terrain, or when the runway is unusually wide, narrow, sloped, or surrounded by misleading terrain.
Derivation
Optical comes from an older Greek word meaning “related to sight.” Illusion comes from a Latin word meaning “to mock or deceive.” Together, optical illusion means something your eyes report in a way that can deceive your judgment. In landing, that matters because the runway picture can look normal while the airplane is actually too high, too low, too close, or too far away.
Why Pilots Care
Optical illusions during landing can cause pilots to misjudge altitude and distance, leading to unstable approaches or runway excursions if not corrected.
Grounding Statement
The key idea is simple: during landing, your eyes are useful, but they are not always enough by themselves.
Intuition Check
Wrong assumption: If the runway looks right, the landing path must be right. Correct idea: Some runway shapes, slopes, lighting, weather, and terrain can make a wrong landing path look normal, so the pilot must cross-check before trusting the sight picture.
Example Sentence 1
Before flying into the unfamiliar mountain airport at night, the pilot reviewed the runway slope in the Chart Supplement as part of preventing landing errors due to optical illusions.
Example Sentence 2
Instructors emphasize how to prevent landing errors due to optical illusions when teaching night flying procedures.