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during night fl ying. The following discussion covers some
of the common situations that cause illusions associated with
night fl ying.
A false horizon can occur when the natural horizon is obscured
or not readily apparent. It can be generated by confusing
bright stars and city lights. It can also occur while fl ying
toward the shore of an ocean or a large lake. Because of the
relative darkness of the water, the lights along the shoreline
can be mistaken for stars in the sky. [Figure 12-7]
On a clear night, distant stationary lights can be mistaken for
stars or other aircraft. Even the northern lights can confuse a
pilot and indicate a false horizon. Certain geometrical patterns
of ground lights, such as a freeway, runway, approach, or
even lights on a moving train can cause confusion. Dark
nights tend to eliminate reference to a visual horizon. As a
result, pilots need to rely less on outside references at night
and more on fl ight and navigation instruments.
Visual autokinesis can occur when a pilot stares at a single
light source for several seconds on a dark night. The result
is that the light appears to be moving. The autokinesis effect
does not occur if the pilot expands the visual fi eld. It is a
good procedure to vary visual focus and not become fi xed
on one source of light.
12-8
Distractions and problems can result from a flickering
light in the fl ight deck, such as anticollision lights, strobe
lights, or other aircraft lights which can cause flicker
vertigo. If continuous, the possible physical reactions can
be nausea, dizziness, grogginess, confusion, headaches, or
unconsciousness. The pilot should try to eliminate any light
source causing blinking or fl ickering problems in the fl ight
deck.
A black-hole approach occurs when the landing is made
from over water or unlighted terrain on which runway lights
are the only sources of light. Without peripheral visual cues
to help, pilots have trouble orienting themselves relative to
Earth. The runway can seem out of position (downsloping or
upsloping) and, in the worst case, result in landing short of the
runway. If an electronic glideslope or visual approach slope
indicator (VASI) is available, it should be used. If navigation
aids (NAVAIDs) are unavailable, careful attention should be
given to using the fl ight instruments to assist in maintaining
orientation and a normal approach. If at any time the pilot is
unsure of his or her position or attitude, a go-around should
be executed.
Bright runway and approach lighting systems, especially
where few lights illuminate the surrounding terrain, may
create the illusion of less distance to the runway. In this
situation, the tendency is to fl y a higher approach. Also,
when fl ying over terrain with only a few lights, it makes the
runway recede or appear farther away. With this situation,
the tendency is common to fl y a lower-than-normal approach.
If the runway has a city in the distance on higher terrain, the
tendency is to fl y a lower-than-normal approach. A good
review of the airfi eld layout and boundaries before initiating
any approach helps the pilot maintain a safe approach
angle.
Illusions created by runway lights result in a variety
of problems. Bright lights or bold colors advance the
runway, making it appear closer. Night landings are further
complicated by the diffi culty of judging distance and the
possibility of confusing approach and runway lights. For
example, when a double row of approach lights joins the
boundary lights of the runway, there can be confusion where
the approach lights terminate and runway lights begin. Under
certain conditions, approach lights can make the aircraft seem
higher in a turn to fi nal than when its wings are level.
Preparation and Prefl ight
Night fl ying requires that pilots be aware of and operate within
their abilities and limitations. Although careful planning of
any fl ight is essential, night fl ying demands more attention
to the details of prefl ight preparation and planning.
Preparation for a night fl ight should include a thorough
review of the available weather reports and forecasts with
particular attention given to temperature-dew point spread.
A narrow temperature-dew point spread may indicate the
possibility of ground fog. Emphasis should also be placed on
wind direction and speed, since wind effects on the aircraft
cannot be as easily detected at night as during the day.
On night cross-country fl ights, appropriate aeronautical
charts should be selected, including the appropriate adjacent
charts. Course lines should be drawn in black to be more
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Weight-Shift Control Aircraft Flying Handbook(138)
