Physiological Acceleration
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Physiological Acceleration
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The acceleration
experienced by a human or an animal test subject in an accelerating vehicle.
See table XI.
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Several different terminologies have been used to describe
physiological acceleration. Since the terminology may be based either on the
action of the accelerating vehicle or the reaction of the passenger, the terms
used are often confusing to a reader without prior knowledge of the system of
terminology used. Probably the most easily understood system is the eyeballs
in, eyeballs out, eyeballs down, eyeballs up, etc., terminology used by test
pilots, which refers to the sensations experienced by the person being
accelerated. Thus, the acceleration experienced in an aircraft pullout or
inside loop is eyeballs down. Note that, in the NASA vehicle (center of
gravity displacement) terminology, this is -az acceleration. Some
physiological-acceleration terminologies designate accelerations in terms of
the equivalent displacement acceleration of the subject as if he were starting
from rest. In such terminologies a man standing up or sitting down on the
surface of the earth is experiencing 1 g of headward acceleration because of
gravity. Other descriptive terms used in this way are footward, forward (the
acceleration experienced by a man pressed into the seat back by an
accelerating vehicle), rearward, leftward, rightward, spineward, sternumward,
and tailward. One terminology based on reaction uses the terms head-to-foot
(the acceleration generated by a pullout in an aircraft), chest-to-back,
foot-to-head, and back-to-chest.
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References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
