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Current Concepts on G Protection Research and Development

Our major objective is to protect the air~
crew against the detrimental effects of +Gz
by developing and assessing equipment and
techniques to enhance high sustained accel-
eration (+Gz) tolerance, and minimize the
hazards of G—LOC. The payoff is reduced
pilot fatigue and improved combat effec—
tiveness. To accomplish these objectives it
is imperative that we learn as much as pos-
sible regarding acceleration physiology and
the influence that protective equipment and
techniques have on acceleration physiology.
Figure 1 illustrates maneuvering accelera-
tion and the resultant inertial force that I
will be discussing throughout this lecture.
+GZ is the correct terminology, however,
sometimes G or G2 will be used as abbrevi-
ations. There are several excellent text-
books which discuss the effects of accelera-
tion in much greater detail (1,9).
The three functional areas of the body most
Figure 1. Maneuvering acceleration and the
equal, but opposite, inertial force that aircrew
are exposed to during flight.
sensitive to acceleration are: the cardiovas—
cular system, the pulmonary system and the
central nervous system (CNS). The cardio—
vascular and pulmonary systems will be
addressed in this lecture and the CNS will
be covered in a following lecture.
Two of the major cardiovascular problems
associated with high sustained +GZ are
maintenance of venous return to the heart
and the maintenance of blood pressure and
blood flow to the brain. Eye—level blood
pressure (ELBP) is known to decrease by
22—25 mmHg/G as a result of the inertial
load on the eye-to—heart hydrostatic column
of blood. Thus, the brain is at a disadvan-
tage when the body is in the upright posi—
tion (+162), where, if mean blood pressure
at heart level is 100 mmHg then brain level
blood pressure will be around 78 mmHg,
assuming a 30 cm eye—to-heart distance
(Figure 2). As +Gz progresses from +16z
to +5Gz then ELBP will decrease from 78
mml-lg to -10 mmHg, resulting in a G—
induced loss of consciousness (G-LOC),
assuming no interventions.