Posted 10-13-2004 at 02:14 AM

G-Force

To understand the effects of the term G-force, you must first know what it is. The "g" in g-force stands for gravity of course, you should all know that, if you don't this article had just told you. But the force has a different definition, it is not the gravity, it's an acceleration. The general meaning that we usually think of is the increase of speed, but that is not the case in a scientific perspective. Acceleration is the change in speed or velocity. So in your daily life, braking a car or turning around a bend is in fact acceleration -- according to science.

Without a doubt, we experience gravity and the g-force everyday. If there was no gravity, we wouldn't be standing here, and this article wouldn't be written. If someone weighs 80kg, under an influence of 1g, you would still weigh 80kg. Now, we in our course of our lives should have experience g-forces higher than that, whether it is in a car, while it is braking, turning or accelerating, or on a rollercoaster, which you would experience Gs of over 2. At 3g, on some rollercoasters, a person weighing 80kg, would be 240kg for several seconds. If you have ever experienced a car crash the g-forces could reach up to 12 g for a few seconds. Pilots in F-16s or similar aircraft would have to endure 9gs for maybe ten to twenty seconds. With 9 gs, you'd weigh 720kg if you were 80kg in 1g.

Before you pilot the fighters, you must prove yourself worthy. In order to prove that you could withstand such a tremendous g-force, you will endure yourself through a centrifuge. A centrifuge is basically a spin dryer, but instead of drying clothes, it makes you feel bad. The harder it spins, the more you will get pushed back into your seat.

Image of F-15

These forces are bound to screw up the human body. Firstly, you would feel difficulty breathing. This is due to the reason that the forces will pull down on your rib cage which in turn pushes down on your lungs, sometimes emptying the air. This although is not the worst effect, it does wear you out and you would feel the lack of air and fatigue. The most dangerous, is the blood that gets pulled by the g-force. The blood gets pulled away from the brain and is moved to your legs and feet. As with that notion, your organs also get pulled down towards your feet, increasing the problem with blood. The blood in order to get to your brain must be forced harder. Because of this, After a short while experiencing high-g turns, you would start to lose your peripheral vision. You would have tunnel vision and experience greying out (your vision becomes black and white). If the g-forces act on the body even longer, you would lose all vision. This loss of vision is termed black out. Should the turn continue the pilot would eventually lose consciousness. This is also called g-LOC (g induced Loss Of Consciousness).

A normal healthy person would start experience loss of vision at around 5-6 g. A way of resisting this is called "strain". You would contract your muscles below your waist and relax the upper body so that you could breathe normally and easily. Your shoulders should be allowed to drop. This should be used just before a turn in flight, so you could prepare for the g-force effects.

There are other less critical effects of the g-force, such as the bursting of blood vessels creating rashes called "geezles" and bruised buttocks from the seat.

There are also consideration of the negative side of g-forces. Both positive and negative must be considered before flying aircraft or combat aircraft. The negative gs have a different effect on the body. Negative gs are usually experienced during a steep dive in an aircraft where you would feel your weight lessening -- the opposite of postive gs. The steeper the dive, the more "weightless" you'd feel. The negative gs has an opposite effect too. These gs would push blood up to your head and brain. Unlike positive gs, where you can withstand 9gs, as little as 2-3gs would cause your eyes' blood vessels to start rupturing. This is called a "red out". A pilot who pushes negative gs would be seeing through bloodshot eyes.

A long period of time under g-forces could result in major bodily harm or problems. Please seek medical attention and refer to a physician before enduring g-forces.

References:
http://www.open2.net/labrats/gforce_science2.htm
http://www.voodoo.cz/falcon/agf.html

Copyright 2004 Steven Lee

What about Negative Gs and Weightlessness?

yup, i just included that, thnx for reminding me, i nearly forgot :bouncing:

No problem. a very good article I must say.