G forces

You can't fly combat aircraft without considering G forces. G forces are the forces of acceleration that pull on you when you change your plane of motion. They are the forces that pilots encouter when engaged in high-speed dogfighting and BFM. There are both positive and negative G forces; both can be dangerous to a fighter pilot. The force of gravity on Earth is used as a baseline for measuring these forces of acceleration.

The force of gravity when you sit, stand or lie down is considered 1 G. In normal activity, we rarely experience anything other than 1 G. But flying a combat aircraft such as the F-16 is not exactly normal. The F-16 is capable of pulling 9 Gs without even trying. But the effect of 9 Gs on your body will be significant. As you pull more Gs, your weight increases correspondingly. Your 10-pound head will weigh 90 pounds when you pull 9 Gs!

If you continue to pull high Gs, the G force will push the blood in your body towards your feet and resist your heart's attempts to pump it back up to your brain. You will begin to get tunnel vision, then things will lose color and turn white, and finnaly everything will go black. You've just experienced the onset of Gravity Induced Loss of Consciousness /GLOC/.

The modern fighter pilot has some aids in helping him overcome the forces of gravity he experiences from combat. The most obvious is the G suit. The G suit uses the principle of pushing the blood back up toward the head during high G maneuvers. The British first used water bladders placed around the legs to help fight against Gs. As the pilot was pressed into his seat from high G forces, the incompressible water would push against his legs and keep the blood from pooling there. Modern G suits use compressed air to force the blood back up towards the pilot's head.

The G force from such maneuvers as pulling out of a dive or banking sharply are called positive Gs because they increase our ordinaly sense of gravity. It is also possible to maneuver in a way that produces negative forces of gravity. These are called negative Gs, and they have a very different effect on you.

If you are flying straight and level and push the nose of the plane down, you will experience your weight lessning. The harder you push the nose down, the more "weightless" you will feel. You are experiencing negative Gs. The effect of negative Gs is to push the blood up into the head, just the opposite of positive Gs. However, while the body can stand up to 9 positive Gs without severe consequences, blood vessels in your eyes will start to rupture when you apply as little as 2 to 3 negative Gs. This is known as redout.. A pilot who pushes too many negative Gs will be seeing the world through bloodshot eyes.

There is a simple way to avoid negative Gs that also gives you much better maneuverability. Instead of pushing forward on the stick to dive /which creates negative Gs/ , roll your aircraft 180 deg. And pull back on the stick. If you roll so that your cockpit is facing toward the ground and then pull back on the stick, you will still be diving toward the ground but will be experiencing positive Gs instead. Your tolerance is much greater to positive Gs.