F-16 cockpit pressure and air

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Unread post27 Sep 2010, 02:41

Is the air supplied to the pilot in F-16s 21% oxygen or 100% oxygen? Also, what psi is the cockpit pressurized to?

This is just a wild guess here, but if the cockpit of the F-16 were pressurized to 15psi (normal sea level pressure), and 100% oxygen were supplied, perhaps the pilot would be able to sustain more G's. Have any studies been done on this?

When a pilot is pulling G's, what is the actual mechanism that causes him to black out- Does the heart simply not have enough pressure to circulate fresh blood to the brain, or does blood literally drain out of the head into the lower body?




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Unread post27 Sep 2010, 03:35

The oxygen system has a diluter lever with two settings: NORM and 100% O2. In the NORM setting, the amount of oxygen delivered is dependent on the cockpit pressure altitude. As the cockpit altitude increases (less pressure), an incrementally higher concentration of oxygen is delivered. The 100% O2 setting delivers pure oxygen and is generally used when the Emergency Power Unit(EPU) is running, all cockpit pressurization is lost or when smoke or fumes are detected in the cockpit.

The cockpit pressurization schedule is ambient pressure up to 8,000 feet. Between 8K-23K, cockpit pressure stays at 8K feet. Above 23K, the Environmental Control System(ECS) maintains a 5psi pressure differential between the cockpit and ambient pressure.

As far as G-Induced Loss of Consciousness(GLOC) goes, the main mechanism for this is lack of blood flowing to the brain. I'm not a physiology expert, but on 100% oxygen, I suppose the blood would be a little more oxygen rich and slightly less blood flow would be needed to stay conscious but I don't imagine a big gain on G-tolerance from this. I'm sure this has been researched and I've never heard the technique to go on pure O2 to increase G-tolerance. As a side note: there is a function called PBG (Pressure Breathing for g) where mask pressure (but not O2 concentration) increases while turning to increase G-tolerance and comfort.
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Unread post27 Sep 2010, 05:42


Bandito pretty much explained things about the regulator and such.

No doubt that pure oxygen could help with GLOC, well, maybe for a second or two.

No matter how oxygenated your blood is, you have to have blood in the brain!!

The gee onset of the Viper, Hornet and Eagle was much greater than previous jets. If you didn't clench your neck and chest muscles early, the blood actually went down from the brain. So the secret was to trap blood for the brain to work with. The gee suit primarily kept blood from pooling in your legs, so it was no good for the new dynamic we experienced.

My student that went to la-la land was looking up ( allowing a straight shot for draining blood from his brain) and then pulled real hard. Suddenly the gee relaxed and I thought he was extending for energy. Then I noted his head bouncing off the canopy, heh heh. He didn't go completely out, but he was on his way.

The only way to help is to do upper body exercises and train yourself to clench throat and chest before you yank, thereby trapping some blood in your brain. There are exercises that involve clenching and breathing that dramatically increase your ability to sustain high gees. But the GLOC episodes we witnessed were primarily due to rapid yanking before clenching all the muscles.

Gums sends....

P.S. Gotta have a beer, Bandito! Maybe at sports bar when Air Force plays.
Viper pilot '79
"God in your guts, good men at your back, wings that stay on - and Tally Ho!"




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Unread post27 Sep 2010, 15:15

Speaking of beer Mr. Gums: It tastes great and ... increases your G-tolerance through increasing your blood pressure!

Lovely stuff.

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