During World War II, aviators were able to fly their aircraft higher and faster than ever before. But this was not without problems. There were accidents that could not be accounted for: pilots were not shot down, there were no malfunctions in the aircraft and yet they were crashing. What was happening was that when pilots were performing high-speed maneuvers such as pulling up hard out of a dive or making fast and tight turns to evade the enemy, they were creating strong centrifugal forces on the lower parts of their bodies.
So what does this mean? It means that as a result of G-forces (or gravitational force), blood pools in the lower part of the body, mainly the legs and abdomen. It’s kinda like when you eat a lot of food and feel sleepy after the meal: some of the blood from your head has gone to your stomach to help the digestion process. But in this case, so much blood has left the head that a pilot begins to feel some physical affects.
Let’s look at some stats. The force that is exerted by earth’s gravity on your body when you are on the ground (or your weight) is 1 G. If you were moving at 3 G’s you would weigh three times your normal weight and at 7 G’s your blood is as heavy as iron.
So without proper protection, the average person would “greyout” at 4 G’s, meaning that he or she would be unable to see color; “blackout” at 5 G’s and at 6 G’s the pilot would be unconscious.
The pilots of WWII that were crashing were experiencing G forces so great that they became unconscious and did not have control over their aircraft. This is called orthostatic intolerance.
To stop this from happening, in the 1940s Wilbur Franks of the University of Toronto was able to create a version of the G suit that you can see me wearing in the photo above.
So how does it work? There are bladders inside the suit at the legs and the abdomen. The tube on the suit receives air from the engine which had a valve that had a spring-mounted weight that would send air into the suit only if the G force was higher than 2 G’s. When the valve was engaged, air would go through the suit, inflate the bladders on the legs and abdomen which would push against the muscles of these body parts. The muscles would then squeeze the blood back up to the heart and up to the head, thus avoiding unconsciousness.
The suit I am wearing in the photograph is a modern issue Anti-G Suit like the ones that pilots in the US Air Force wear today. They wear it with a flight suit underneath, gloves, boots and of course, a helmet with oxygen mask.