(1) Dim runway markers: You should expect the illusion of being
higher and farther away from the runway environment than you actually are.
(2) Bright runway markers: You should expect the illusion of being
lower and closer from the runway environment than you actually are.
(3) Differing intensities in runway markers: Differing intensities
of left and right markers will create an illusion that an aircraft is being
banked when it is actually level.
(4) The transition from low-intensity lighting to a runway
illumination environment: The transition from an environment of relatively
low illumination (such as a large body of water) to an environment of
comparatively high illumination (such as a lighted airfield in a large city)
will also cause a visual illusion that differs from the actual situation.
This illusion (called a black-hole approach) may cause an approach to be
short of the desired point of landing because of the apparent closeness of
the runway environment.
d. Runway Characteristics. Visual illusions, like visual perceptions,
are dependent upon past experience; therefore, runway characteristics
different from past experience may create a visual illustration.
(1) Narrower than normal runway: The distance to and the height
above a narrower than normal runway will appear to be greater than they
actually are.
(2) Wider than normal runway: The distance to and the height above a
wider than normal runway will appear to be less than they actually are.
e. Runway Contrast. You must be
alert for visual illusions whenever
the color of the runway is similar to
the surrounding terrain. The lack of
contrasting colors may make distances
and altitudes appear greater than they
actually are. The following are some
examples where the lack of color
contrast may be a factor.
(1) Snow: The runway and terrain are covered with snow.
(2) Reduced illumination: An unlighted runway during periods of
reduced illumination.
(3) Intense illumination: A concrete runway or sandy terrain during
periods of intense illumination (especially if the runway is wet).
5.
OVERCOMING ILLUSIONS
The keys to overcoming visual illusions are awareness of conditions
under which illusions are apt to occur and good prior planning.
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