Visual illusions in the landing phase of flight can cause hazardous misjudgments. These illusions are, however, avoidable with proper preparation, awareness, and anticipation.
To supplement vision use the glideslope (if available), PAPI or VASI lighting. Be conscious of your altimeter and consult the AFD to determine runway slope. At an unfamiliar field it may be necessary to make a low pass to inspect the runway and judge the approach perspective. Listed are five landing illusions that may be encountered.
- Runway Width Illusion: A narrower than usual runway can create the illusion that the aircraft is higher than its actual altitude. The result can be a tendency to fly the approach lower than a safe altitude.
- Terrain Slope Illusion: An upsloping runway and or surrounding terrain can create the sensation of the airplane being higher than necessary. The result is a tendency to fly a lower approach. A downsloping runway can create the opposite effect. This presents the possibility of overshooting the runway.
- Featureless Terrain Illusion: An absence of ground features when approaching over water, darkened areas or snow can create an illusion that the airplane is higher than its actual altitude. The result is to fly a dangerously low approach.
- Atmospheric Illusions: Rain can create the illusion of greater height. Haze can cause the runway to seem farther away than it really is. In both cases a dangerously low approach may result.
- Ground Lighting Illusions: Approach and runway lighting on high or bright illumination can create the illusion of less distance to the runway. The result would be to fly a higher approach. Conversely lights on a low setting may have the opposite effect.
Reference: AIM 8-1-5 Illusions in Flight
Wisdom of Will Rogers: Good judgment comes from experience, and a lot of that comes from bad judgment.
These safety tips are provided by the WCFC Safety Committee. They are intended to stimulate thought and discussion about flight safety and do not necessarily represent club policy nor are they intended to replace instruction from a qualified instructor.