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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.