background image

AIM

10/12/17

8

−1−6

Fitness for Flight

in a nose up attitude. The disoriented pilot will push
the aircraft into a nose low, or dive attitude. A rapid
deceleration by a quick reduction of the throttles can
have the opposite effect, with the disoriented pilot
pulling the aircraft into a nose up, or stall attitude.

(e) Inversion illusion. An abrupt change

from climb to straight and level flight can create the
illusion of tumbling backwards. The disoriented pilot
will push the aircraft abruptly into a nose low attitude,
possibly intensifying this illusion.

(f) Elevator illusion. An abrupt upward

vertical acceleration, usually by an updraft, can create
the illusion of being in a climb. The disoriented pilot
will push the aircraft into a nose low attitude. An
abrupt downward vertical acceleration, usually by a
downdraft, has the opposite effect, with the
disoriented pilot pulling the aircraft into a nose up
attitude.

(g) False horizon. Sloping cloud forma-

tions, an obscured horizon, a dark scene spread with
ground lights and stars, and certain geometric
patterns of ground light can create illusions of not
being aligned correctly with the actual horizon. The
disoriented pilot will place the aircraft in a dangerous
attitude.

(h) Autokinesis. In the dark, a static light

will appear to move about when stared at for many
seconds. The disoriented pilot will lose control of the
aircraft in attempting to align it with the light.

3. Illusions Leading to Landing Errors.

(a) Various surface features and atmospheric

conditions encountered in landing can create illusions
of incorrect height above and distance from the
runway threshold. Landing errors from these
illusions can be prevented by anticipating them
during approaches, aerial visual inspection of
unfamiliar airports before landing, using electronic
glide slope or VASI systems when available, and
maintaining optimum proficiency in landing
procedures.

(b) Runway width illusion. A narrower-

than-usual runway can create the illusion that the
aircraft is at a higher altitude than it actually is. The
pilot who does not recognize this illusion will fly a
lower approach, with the risk of striking objects along
the approach path or landing short. A wider-than-
usual runway can have the opposite effect, with the

risk of leveling out high and landing hard or
overshooting the runway.

(c) Runway and terrain slopes illusion. An

upsloping runway, upsloping terrain, or both, can
create the illusion that the aircraft is at a higher
altitude than it actually is. The pilot who does not
recognize this illusion will fly a lower approach. A
downsloping runway, downsloping approach terrain,
or both, can have the opposite effect.

(d) Featureless terrain illusion. An

absence of ground features, as when landing over
water, darkened areas, and terrain made featureless
by snow, can create the illusion that the aircraft is at
a higher altitude than it actually is. The pilot who does
not recognize this illusion will fly a lower approach.

(e) Atmospheric illusions. Rain on the

windscreen can create the illusion of greater height,
and atmospheric haze the illusion of being at a greater
distance from the runway. The pilot who does not
recognize these illusions will fly a lower approach.
Penetration of fog can create the illusion of pitching
up. The pilot who does not recognize this illusion will
steepen the approach, often quite abruptly.

(f) Ground lighting illusions. Lights along

a straight path, such as a road, and even lights on
moving trains can be mistaken for runway and
approach lights. Bright runway and approach lighting
systems, especially where few lights illuminate the
surrounding terrain, may create the illusion of less
distance to the runway. The pilot who does not
recognize this illusion will fly a higher approach.
Conversely, the pilot overflying terrain which has few
lights to provide height cues may make a lower than
normal approach.

8

−1−6. Vision in Flight

a. Introduction. Of the body senses, vision is the

most important for safe flight. Major factors that
determine how effectively vision can be used are the
level of illumination and the technique of scanning
the sky for other aircraft.

b. Vision Under Dim and Bright Illumination.

1. Under conditions of dim illumination, small

print and colors on aeronautical charts and aircraft
instruments become unreadable unless adequate
cockpit lighting is available. Moreover, another
aircraft must be much closer to be seen unless its
navigation lights are on.