How to Prevent Landing Errors Due to Visual Illusions

Pilots can take action to prevent these illusions and their potentially hazardous consequences if they:

1.        Anticipate the possibility of visual illusions during approaches to unfamiliar airports, particularly at night or in adverse weather conditions. Consult airport diagrams and the Airport/Facility Directory (A/FD) for information on runway slope, terrain, and lighting.
2.        Make frequent reference to the altimeter, especially during all approaches, day and night.
3.        If possible, conduct aerial visual inspection of unfamiliar airports before landing.
4.        Use Visual Approach Slope Indicator (VASI) or Precision Approach Path Indicator (PAPI) systems for a visual reference, or an electronic glide slope, whenever they are available.
5.        Utilize the visual descent point (VDP) found on many non-precision instrument approach procedure charts.
6.        Recognize that the chances of being involved in an approach accident increase when some emergency or other activity distracts from usual procedures.
7.        Maintain optimum proficiency in landing procedures.

Visual Approach Slope Indicator (VASI): A system of lights arranged to provide visual descent guidance information during the approach to the runway. A pilot on the correct glide slope will see red lights over white lights.

Precision Approach Path Indicator (PAPI): Similar to the VASI but consisting of one row of lights in two or four-light systems. A pilot on the correct glide slope will see two white lights and two red lights.