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Feature Article: Night Illusions
Runway and approach light illusions will always be a problem
if you are in an unfamiliar area. For this reason it is always
desirable to make a daylight familiarization flight to an airport
before a first time night arrival. Night has its own illusions
that are covered in the night flight lessons. The distance of
lights is greatly affected by the relative clearness and haze
existing. A region of no lights such as might exist off the end
of a runway toward the ocean can cause disorientation because
of IFR illusions. The best solution is to go on instruments until
established inland at altitude.
Variable Visibility
If, while on approach, you should suddenly face reduced visibility
you will get an illusion of a sudden pitch up in aircraft attitude.
Failing to recognize this illusion will lead to an instinctive
and abrupt descent in the approach flight path.
Your ability to determine distance is greatly affected by haze.
It is not unusual to call a distance at over twice the actual
distance. The sudden appearance of bright lights during an a night
approach through haze will create the illusion that the airport
is much closer than previously realized. This results in a high
approach.
Low
If there is no VASI or VAPI for vertical guidance if you get too
low the runway lights will begin to disappear. A steep approach
is always better at night. An arrival at an airport with and approach
lighting system (ALS) tends to be lower and at a shallower angle
than otherwise. Low approach results when runway is approached
over dark area. Don't use landing light until close to ground.
The visual cues used for a normal night landing seem much the
same as you get with a rapid increase in sink rate.
Inverted
If there is a strong crosswind and you are crabbing to the runway
instead of slipping you will get the illusion of being inverted.
If the airport is well lighted in a surrounding dark area you
will have an illusion of being higher than you actually are. Again
a steep approach has much advantage.
High
Rain on the windshield will give the illusion of being higher
than you are. If you mistake roadways for runways. It will give
illusion of being quite close when lights are bright. High approach
results.
Rising
If you are low and pitch the nose up as a correction or through
the use of flaps, the illusion will indicate that you are rising.
Any reduction of power will cause you to land short.
Diving
At night, banking into or away from a line of lights will give
the illusion that a dive or a climb is occurring. The same dive
or climb illusion can happen by a change in aircraft pitch occurs
while flying toward a light.
A 10 degree bank with only the approach lights visible can cause
an illusion that the lights are sloping from above.
Distance
Lights that appear dim, as seen through haze, will be reported
as more distant than they are. Example: I once reported an airport
as in sight from twelve miles when the tower had me on radar at
only five miles.
Last Modified April 14, ©2021 TAGE.COM
