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The Air Force believes that it's solved the years-long mystery of why F-22 pilots have suffered potentially dangerous, hypoxia-like symptoms aboard the world's most advanced jet fighter.
And the answer is so insanely simple, some Congressmen don't believe it.
It's primarily clothing!
According to Congressional Testimony by NASA and Air Force experts earlier this month, the problem lies with an inflatable combat vest that was worn -- in combination with rubberized cold-weather survival gear needed for ejection by pilots over cold water. This combination of flight gear was worn by crews flying out of only two bases in the world:
Joint Base Elmendorf-Richardson here in Alaska, and Langley Air Force Base in Virginia. It just so happens that these are the only two groups of pilots who suffered hypoxia anomolies aboard the F-22.
The vest, when combined with the bulky cold weather exposure clothing worn by pilots at those two bases (to help them survive immersion in cold water in a ditching or ejection), constricted the chest. Constricted lungs are very bad news for pilots during high-g maneuvers, such as sharp turns. That's when pilots most need an adequate supply of oxygenated blood to remain in their heads. During those high-g maneuvers blood tends to rush out of your brain and pool in your stomach and legs.
The clincher to solving the mystery was this:
Air Force testing in ground centrifuges -- using the cold weather gear with the inflatable vests -- showed that pilots could not inhale the same volume of oxygen into their lungs, whenever they wore rubberized cold weather suits. And being able to breathe fully is vastly important when you're under high g-loading at high altitude.
The ground-based tests showed that the Air Force could actually induce hypoxia-like system in pilots at sea level under high g-forces. Graphs of oxygen-volume also showed those pilots could not fill their lungs with air their chests were constricted by the combination of cold weather clothing and the inflatable vests.
The Air Force plans to change a valve in the Upper Body Pressure Garment so that it inflates to a suitable pressure when worn over cold-weather emergency gear.
The agency also plans to install a 15.4 pound back-up oxygen generating system in the cockpit to help pilot -- with a sustained burst of pure oxygen -- when they are becoming hypoxic.
Another aspect of the fix is attaching a biomedical sensor to the F-22 pilots' ear. Itwill continuously measure the oxygen-saturation of his blood so that he knows when to manually increase O2 flow in his mask.
But how could something like this have happened in the first place?
How is it that the Air Force could have failed to take into account that ruberized coldwater survival suits would have constricted a pilot's chest in the F-22. And why hasn't this problem cropped up before in previous American fighter jets?
Experts told a Congressional Committee on September 14th that the F-22 is different from all previous fighters. Itroutinely flies at altitudes above 50,000 feet. The plane's maximum ceiling is classified, but iexperts say the F-22 flies much higher than either the F-15 or the F-16. It also flies much higher than the F-18.
General Gregory Martin (USAF-Ret) testified before Congress on September 14th that, in fact, the F-22's high-altitude capabilities are more comparable with a U-2 Spy plane, or the SR-71 reconnaissance aircraft than they are to a conventional fighter.
Both spy planes fly so high that pilots are required to wear full pressure-suits. Those suits look just like the orange spacesuits -- which used to be worn by astronauts for launch aboard the space shuttle.
But a fighter pilot cannot where a bulky space suit. For one thing, the helmet of a spacesuit is attached to a neck ring, and that means the helmet is immobile. In a dog-fight, the pilot would only be able to see in front of him -- posing a significant risk that he could be shot-down by an enemy coming in from behind or from the side -- an enemy he might never see.
In addition, even though the F-22 flies at extremely high altitude for a jet-fighter, it's platic canopy cannot be fully pressurized. It must be lightly pressurized in case a bullet -- fired at the pilot from another aircraft -- comes crashing through the plexiglas. If the canopy suffered a bullet strike -- while the cabin was fully pressurized, with the plane was flying above 50,000 feet -- there would be a sudden, explosive decompression, which would be very dangerous for a pilot.
That compromise -- of having to lightly pressurize the cockpit at high altitude -- leaves the pilot utterly dependent on the proper flow of oxygen through his relatively flimsy face mask. (At least that mask is flimsy compared to an astronaut's fully-sealed space helmet).
So in summary what we have with this, an jet fighter that flies at extremely high altitude, a cabin which -- for safety reasons -- cannot be fully pressurized, and a fighter pilot not permitted to wear a full space suit at those extreme altitudes.
When pilots are only wearing a sealed facemask to protect them from hypoxia, there had better be nothing to constrict their chest when they try to take a full breath of air under the strain of high-g maneuvers. In this case, the combination of an improperly inflated upper pressure garment, worn over a bulky, rubberized exposure suit, did constrict the breathing. That led to hypoxic symptoms.
The problem is compounded by the fact that hypoxia symptoms can be so subtle -- and accompanied by a euphoric sense of well-being -- that a pilot may not recognize he's in trouble until it's too late.
In fact, that may have been what happened in the fatal crash of an F-22, flying out of J-BER, back in November 2010.
Captain Jeff Haney apparently suffered hypoxic symptoms while flying 100 miles north of Anchorage. He impacted the ground, unable to activate his emergency oxygen system. Pilots do train for this contingency -- to recognize hypoxia and then act to take emergency actions to counteract it. But carrying out the emergency procedures can still be difficult in an hypoxic state. In fact, one F-22 pilot, speaking to the news broadcast "60 Minutes" earlier this year said that he had suffered an hypoxic incident aboard the F-22. He went on to say that it took all of his concentration to activate the emergency system.
Another problem may have contributed to hypoxic symptoms aboard the F-22. The Air Force believes that a computer algorithm, which controls the flow of oxygen to a pilot's mask, may have had a flaw in it in earlier versions of the F-22. Under certain flying conditions, the computer system might have failed deliver enough oxygen to a pilot.
The algorithm has since been corrected. In addition, the Air Force has now decided to install a back-up oxygen system in the plane. In earlier models of the F-22, this back-up oxygen system was not installed. The Air Force was fearful that at a weight of 15.4 pounds, the back-up O2 system might diminish the performance of the aircraft. High performance, in the form of tight turns and maximum climbing speed, is essential if a jet if it is to survive aerial combat with other jets.
But, with hindsight, the Air Force has now determined that the weight penalty of the back-up O2 system is insignificant. In testimony before Congress, Air Force officials testified that the F-22 has such high performance capability, the agency is now opting for increased safety.
In its brief history as an operational aircraft, a history extending back to 2005, F-22 pilots have suffered one hypoxia-like incident per thousand sorties. That doesn't sound that much, but it's a rate twice as high as the F-16 (whjch flies at much lower altitude and which has a back-up oxygen system).
With the alteration of the upper body pressure garment -- to compensate for the bulkiness of the cold water survival gear, the Air Force now believes it has a handle on the problem of hypoxia-like symptoms on the F-22.
The plane returned to service on September 21, 2011(after a 5-month-grounding in the summer of 2011). In that year, there has been some good news. There have been no hypoxic incidents aboard the aircraft in the past 5 months -- since March 2012.
The Air Force says the F-22 costs $143 million dollars apiece -- making it, by far -- the most expensive fighter aircraft in the world.
But if you take the F-22's production costs ($79 billion) and divide it by the 195 fighters that have been built, you arrive at a much higher cost -- $405 million dollars per plane.
Whichever figure is right, the Air Force now believes it has a handle on the F-22 oxygen problem.
Time will tell if military officials are right.