Print 19 comment(s) - last by im4aqt.. on Aug 2 at 3:00 PM

Faulty valve could contribute to hypoxia-like symptoms experienced by some pilots

The United States Air Force's premier air superiority fighter is the F-22 Raptor. However, the F-22 has had problems over the last few years with pilots at times experiencing hypoxia-like symptoms during flight. The F-22 fleet was grounded while an investigation into the problem was conducted.
Ultimately, USAF found no hard evidence on what was causing the symptoms in some pilots and the aircraft were returned to the skies with no fixes applied. 
The Air Force has now announced that after further review, it has discovered a faulty valve on the pressurized vests F-22 pilots wear during flights. The valve will be replaced by the end of the year and pilots are currently not wearing the pressurized vests during flights. The move to replace the valve and ban the vests from being worn currently is an attempt to help address some pilot complaints of nausea and dizziness while operating the fighter.
The valve in question connects the plane's onboard oxygen generation system to the vest and inflates the vest to protect pilots during high G maneuvers. However, the valve has a flaw because the vests to be constantly inflated even when the aircraft is operating at lower altitudes where the vest wasn't required.

"It [the vest] restricts his breathing, it restricts his ability to do normal inhalation and exhalation. ... The pressurization schedule in the F-22 inflates prematurely, so we removed this,” Maj. Gen. Charles Lyon said at a Pentagon briefing Tuesday. Lyon is the director of operations for Air Combat Command. Air Force officials believe that the pressure on the chest of the pilot due to the faulty valve could cause the symptoms of hypoxia that some pilots are experiencing.
Defense News reports that within the next month the USAF will start testing a new valve that will provide more tension and restrict airflow into the pressure vests until the airflow is needed.
Lyon also went on to say that there was no evidence that the faulty valve contributed to the fatal F-22 crash resulting in the death of pilot Capt. Jeff "Bong" Haney.

Source: Defense News

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Create a pressurized cabin.
By im4aqt on 8/1/2012 5:02:53 PM , Rating: 1
The problem could effectively reduced to zero by simply installing a pressurized cabin for the pilot. That way toxins would no longer be forced into the bloodstream in high G situations.

RE: Create a pressurized cabin.
By inperfectdarkness on 8/2/2012 7:34:41 AM , Rating: 2
you don't seem to understand the fundamental principles of how a fighter jet affects its pilot.

the cabins are already pressurized--usually to ~20-30k feet. the oxygen supply the pilot breathes is pressurized to ~5-8k feet or so.

in a high-g maneuver, the danger to the pilot isn't from "toxins" in the blood, it's from g-loc (gravity-induced loss of consciousness). blood pools in the lower extremities during a high-g turn, which causes the blackout. the solution is to keep blood in the head/arms.

pressure suits are designed to assist this by squeezing the lower extremities to "push" blood further up into the body. pressurizing the entire cabin will do nothing to counter this, as the pilot's entire body would still be under one constant ambient pressure.

you need to do your homework.

RE: Create a pressurized cabin.
By im4aqt on 8/2/2012 3:00:55 PM , Rating: 2
I'm sorry for the misunderstanding. My assertion is that the materials used in construction of the oxygen breathing system decompose at a molecular level during high G situations. This causes the pilot to be breathing not only oxygen but a soup of gases that are scrubbed from the breathing system. By pressurizing the cabin to a point where no breathing system is required will alleviate the situation.

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