A
suit of force
The
anti-gravity garment – or G-suit – has revolutionised flying
and an Australian played a key role in its evolution.
IT HAS been around since World War II, but
the anti-gravity garment – or G-suit as it is more commonly known
– is still one of the most essential items for pilots operating
high performance aircraft.
The G-suit is a tight-fitting wraparound garment that covers
parts of the body below the heart. It is designed to retard the
flow of blood to the lower body in reaction to extreme acceleration
or deceleration, resulting in positive gravity (G) forces.
Positive G forces are usually encountered when pulling an aircraft
out of a dive or during a turn, acting on the body directionally
from head to toe.
The effects of gravity forces on the body first became apparent
less than two decades after the Wright Brothers’ first powered
flight when pilots experienced “greyouts” (dimming of vision
and loss of peripheral vision) during steep turns in military
aircraft.
With higher performance aircraft came a greater awareness of the
significance of G forces. In the quarter century between the
global conflicts of World Wars I and II, the maximum acceleration
of 4G had increased to 9G forces, causing many cases of gravity-induced
loss of consciousness.
Australian physiologist Frank Cotton played a central role in
the evolution of the garment in the 1930s and 40s. He devised
a way of determining the centre of gravity of a human body, which
made it possible to graphically record the displacement of mass
within the body under different conditions such as rest, respiration,
posture and exercise.
He later used this technique to pioneer suits that were inflated
with air and regulated by G-sensitive valves. American Wilbur
Franks undertook similar work which led to the first G-suit used
in combat during World War II.
It gave Allied pilots a major tactical advantage as they were
able to tolerate greater G-forces to outmanoeuvre their opponents.
After 1942, the new invention was used exclusively by US fighter
pilots in the Pacific and led to the rapid development of the
centrifuge.
The G-suit used by the Air Force of today has encased bladders
that automatically inflate to increase body constriction after
two Gs.
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Pressure
applied to the body is proportional to the amount of Gs being
experienced, ensuring adequate blood supply to the upper body
and head to preserve circulation, vision and mental alertness
until level flight has resumed.
