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时间:2010-05-10 19:35来源:蓝天飞行翻译 作者:admin
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or the natural horizon may at times become obscured by smoke, fog, smog,
haze, dust, ice particles, or other phenomena, although visibility may be above VFR
minimums. This is especially true at airports located adjacent to large bodies of water
or sparsely populated areas, where few, if any, surface references are available. Lack
of horizon or surface reference is common on over-water flights, at night, or in low
visibility conditions.
•••


•• Visual Illusions
Visual illusions are familiar to most of us. As children, we learned that railroad tracks
—contrary to what our eyes showed us— don’t come to a point at the horizon. Even
under conditions of good visibility, you can experience visual illusions including:
Aerial Perspective Illusions may make you change (increase or decrease) the slope
of your final approach. They are caused by runways with different widths, upsloping
or downsloping runways, and upsloping or downsloping final approach terrain. Pilots
learn to recognize a normal final approach by developing and recalling a mental
image of the expected relationship between the length and the width of an average
runway (Figure 2).
A final approach over a flat terrain with an upsloping runway may produce the
visual illusion of a high-altitude final approach. If you believe this illusion, you may
respond by pitching the aircraft nose down to decrease the altitude, which, if performed
too close to the ground, may result in an accident (Figure 3).
A final approach over a flat terrain with a downsloping runway may produce the
visual illusion of a low-altitude final approach. If you believe this illusion, you may
respond by pitching the aircraft nose up to increase the altitude, which may result in
a low-altitude stall or a missed approach (Figure 4).
Figure 2
Figure 3
Figure 4
A final approach over an upsloping terrain with a flat runway may produce the
visual illusion of a low-altitude final approach. If you believe this illusion, you may
respond by pitching the aircraft nose up to increase the altitude, which may result in
a low-altitude stall or a missed approach (Figure 5).
A final approach over a downsloping terrain with a flat runway may produce the
visual illusion of a high-altitude final approach. If you believe this illusion, you may
respond by pitching the aircraft nose down to decrease the altitude, which, if performed
too close to the ground, may result in an accident (Figure 6).
A final approach to an unusually narrow runway or an unusually long runway
may produce the visual illusion of a high-altitude final approach. If you believe this
illusion, you may respond by pitching the aircraft nose down to decrease the altitude,
which, if performed too close to the ground may result in an accident (Figure 7).
A final approach to an unusually wide runway may produce the visual illusion of a
low-altitude final approach. If you believe this illusion, you may respond by pitching
the aircraft nose up to increase the altitude, which may result in a low-altitude stall
or a missed approach(Figure 8).
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
A Black-Hole Approach Illusion can happen during a final approach at night
(no stars or moonlight) over water or unlighted terrain to a lighted runway beyond
which the horizon is not visible. In the example (Figure 9), when peripheral visual
cues are not available to help you orient yourself relative to the earth, you may
have the illusion of being upright and may perceive the runway to be tilted left and
upsloping. However, with the horizon visible (Figure 10), you can easily orient yourself
correctly using your central vision.
A particularly hazardous black-hole illusion involves approaching a runway under
conditions with no lights before the runway and with city lights or rising terrain
beyond the runway. These conditions may produce the visual illusion of a highaltitude
final approach. If you believe this illusion, you may respnd by lowering your
approach slope (Figure 11).
Figure 11
􀁲 􀁳
The Autokinetic Illusion gives you the impression that a stationary object is moving
in front of the airplane’s path; it is caused by staring at a fixed single point of light
(ground light or a star) in a totally dark and featureless background. This illusion
can cause a misperception that such a light is on a collision course with your aircraft
(Figure 12).
False Visual Reference Illusions may cause you to orient your aircraft in relation
to a false horizon; these illusions are caused by flying over a banked cloud, night flying
 
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