G-Force refers to either the force of gravity on a particular celestial body or the force of acceleration anywhere. G-force is measured in G’s and one G is equal to the force of gravity at the earth’s surface. Funny to know that the average sneeze creates a G-force of 2.9 and a slap on the back can equal about 4.1 G’s
The invention of the airplane gave way to the extreme G-forces that we are familiar with today. G’s first became a concern during WWI, when pilots began mysteriously losing consciousness during dogfights. In 1919 a doctor wrote up the phenomenon, calling it “fainting in the air”. The amount of G’s that are tolerable vary by individual and a tolerance can be built up over time.
If a pilot pulls 10 G’s, it would be his weight x 10 and the sum would be the amount of weight pressing against his body. If the pilot weighted 200 pounds and pulled 10 G’s, 2,000 pounds of pressure would be exerted on his body.You can see why it would be important for an aerobatic pilot who is competing or flying air shows to rest between flights. Kirby says, “I have about three hours recovery time between practice flights.” Flying an air show Kirby will see anywhere from 10 positive to 5 or 6 negative G’s and at an Air Race the range would be 12 positive with almost no negative G’s. Aerobatic competition is a little different in that there is more negative G’s involved, as many as 8 negative and 10 positive. Kirby often says, “At 10 G’s, it’s hard to breathe and feels like a house is sitting on your chest.” That’s a ton of pressure, literally!
When a person begins to lose consciousness due to positive G’s, this is called G-lock. The vision starts to narrow and become gray, that’s where an experienced aerobatic pilot, recognizing the signs, might ease up on the stick. The problem is that with the high tech mono-planes and fighters the onset is so rapid that the pilot might never see it coming!
Negative G’s are a different story all together. No one really knows what the long tem effects of negative G-forces are on the human body.
So next time you watch the Red Bull Air Race or attend an air show, know the pilots are taking a beating from those G-forces!
