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AIM 

6/17/21 

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. 

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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. 

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Fitness for Flight