Capt. Matthew Taranto, aerospace and operational physiologist

Steve Marcus

Air Force Capt. Matthew Taranto, an aerospace physiologist, explains how pilots are trained to cope with G-forces acting on their bodies.

By Marshall Allen (contact)

Tuesday, Oct. 6, 2009 | 2 a.m.

Air Force jets soar faster than the speed of sound during training exercises above Southern Nevada, banking, accelerating and rolling to avoid simulated fire.

The F-16s and F-22s are designed for that kind of action. Not so the human body.

Capt. Matthew Taranto, an aerospace and operational physiologist at Nellis Air Force Base, studies the effect of flight on the body. He trains air crews to endure the extreme stress brought on by high-performance flight.

What are G-forces?

G-forces are the measure of acceleration pressing straight down on the body from your head to your toe. If your chair had a scale sitting under it, adding one additional G-force would be the equivalent of adding your body weight to the scale. So 9-Gs, the maximum we train Air Force crew members to endure, would equal nine times a person’s body weight.

What do G-forces do to the body?

Above four or five Gs — the average person’s resting tolerance — the blood pressure in the head decreases because blood flows to the lower extremities. If that happens, the brain loses oxygen and the pilot may lose his vision or pass out.

So how does a pilot fight the loss of oxygen to his brain?

He wears an anti-G suit, a lower body garment that increases pressure in the lower body by inflating with air as the Gs increase. And he does the anti-G straining maneuver.

That entails squeezing his lower body, increasing the pressure there so blood stays in the heart and lungs. Then the pilot keeps his upper body relaxed while using his respiratory system like a pump, strategically inhaling and exhaling to cycle oxygenated blood between the lungs and brain.

How long can a pilot endure nine Gs?

An F-16 or F-22 pilot must be able to maintain sustained nine Gs for at least 15 seconds. He could maintain consciousness and cognitive function beyond that, but it’s hard to do in the airplane and he wouldn’t enjoy it.

Pilots can endure extreme Gs, but I get sick on merry-go-rounds. Why?

The inner ear is filled with fluid that sends signals to the brain when there’s a change in orientation. When you’re on a merry-go-round, the inner ear acclimates to the spinning, but your eyes are taking in the motion.

When you jump off the merry-go-round, your inner ear — still acclimated to the merry-go-round — tells you the whole world is spinning, but your eyes tell you the opposite. Those mixed sensory signals can cause nausea.

To get over your sensitivity you’ve got to keep doing it over and over again. The same is true with pilots and G-forces. They build a tolerance when their bodies are repeatedly exposed to them.

Do pilots have a superhuman ability to handle G-forces?

As long as people meet medical standards, they can usually be trained to handle this.