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​If you are familiar with the airports in your local area, you might have noticed some runways are narrower than others or some maybe up or down slopping. In Southern California we have a few runways that are narrow and or upsloping.

One good example is the Catalina Island airport runway. This runway has many facts; upsloping (when landing Runway 22), narrow at only 75 feet wide than a typical runway, along with cliffs on either end to include other facts. This makes it difficult to judge with many visual illusions.

Whereas the Flabob airport (KRIR) runway is only 50 feet wide. This airport is just a couple mile north of Riverside Airport.

Runway Illusions

If flying into an airport with a narrow-than-usual runway, which can create an illusion that the aircraft is at a higher altitude than it actually is. Pilots need to be aware of this illusion, to avoid flying a lower approach, which can have the risk of striking objects on short final such as, power lines, trees, poles, towers etc.

Up sloping runways and up sloping terrain, even both can give the illusion that the aircraft is at a higher altitude than it actually is. Pilots that do not recognize this illusion will fly a lower approach. Pilots should also be aware that down sloping runways and terrain have an opposite effect.

Thing a pilot can do to prevent landing errors caused by optical illusions:

  • Recommend flying an aerial visual inspection of any unfamiliar airport prior to landing.

  • Always use either a Visual Approach Slope Indicator (VASI) or a Precision Approach Path Indicator (PAPI) when available.

  • Rely on your instruments and reference the altimeter frequently.


The leans are a common illusion that happens during flight, caused by a sudden return to level flight after a gradual or prolong turn that went unnoticed by a pilot. This happens when the human body is exposed to a shallow turn of 2 degrees per second or less, which is below the detection of the semicircular canals in the inner ear.

A pilot may lean in the direction of the turn, to correct the perception of vertical posture.


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