BY ORDER OF THE SECRETARY OF THE AIR FORCE AIR FORCE ...

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AFMAN 11-217V1 3 JANUARY 2005
and equilibrium. This information is processed automatically at very high rates and without
conscious effort. The conscious mind employs central (focal) vision to determine spatial
orientation by comparing sensory inputs to known experiences. In contrast to the speedy
processes of the subconscious, information processed in the conscious mind is relatively
slow, requiring active thought, and is normally very accurate. For earthbound activities, our
subconscious orientation system receives adequate information from the sensory systems.
However, when a person is subjected to the flight environment, these sensory systems are no
longer adapted to the environment and may provide the subconscious mind with false
information about its orientation in space. For example, when flying in IMC or without
reliable external attitude or motion cues, only the conscious mind, through the use of focal
vision and attention to flight instruments, can correctly determine true orientation.
17.2.1. Vestibular System (Figure 17.2). The vestibular system contains the primary
organs of equilibrium and thus plays a major role in the sensation of motion and spatial
orientation. It aids vision by providing angular and linear acceleration information to
stabilize the eyes when motion of the head and body would otherwise result in blurred
vision. On the ground, the vestibular system provides reasonably accurate perception of
position and motion. In flight, however, the ability to sustain motion in the aircraft
results in a mismatch between the vestibular input of the inner ear and the actual aircraft
motion. To understand how this vestibular information can be erroneous, one must look
at its two sensors: the semicircular canals and the otolith organs of the inner ear.
Figure 17.1. Organs of Equilibrium.