The U.S. Air Force has instructed pilots of the F-22 Raptor to stop wearing a pressure vest during routine flights as the service continues to investigate oxygen- deprivation incidents on the Lockheed Martin Corp. fighter jet.
"Recent testing has identified some vulnerability and reliability issues in the upper pressure garment worn by F-22 pilots," Lieutenant Colonel Edward Sholtis, a spokesman for the Air Combat Command, said today in an e-mailed statement. He said the Air Force is working to correct the problem.
The Air Force has been trying to figure out why F-22 pilots have suffered from hypoxia-like symptoms that include dizziness and disorientation. There have been 11 unexplained incidents related to a lack of oxygen since the plane resumed flying last year after a four-month halt for safety concerns.
"The upper pressure garment is not 'the' cause of physiological incidents, and we still have other variables to work through before we can determine what the major factors are and how they interact to produce the number of unexplained incidents we've seen," Sholtis said.
The Air Force has been studying whether pilots are getting enough oxygen and whether the air they breathe may be contaminated.
The pressure vest is the upper portion of the "G suit" worn by pilots to withstand high levels of acceleration, or "G" forces.
Brigadier General Daniel Wyman, the Air Combat Command's surgeon general, said in an June 11 interview that investigators are examining all "life-support garments" used by F-22 pilots.
While Wyman gave no hint of a flaw in the pressure vest, he said investigators found "the life-support equipment was not appropriately fitted" for pilots "and actually may have restricted their ability to breathe."
"It was like a tight-fitting garment that would not fully allow you to expand your chest," he said. "We've gone back out to the field, insuring that everyone was wearing their equipment appropriately."
Sholtis said the Air Force is looking at the flight suits worn by F-22 pilots in combination with the pressure vests.
"Testing has determined that the upper pressure garment increases the difficulty of pilot breathing under certain circumstances," Sholtis said. "We're also looking at the layering of other aircrew flight equipment as contributing to that difficulty."
The Air Force isn't ready to label the vest as a cause of the hypoxia symptoms because officials are still gathering data, according to a government official briefed on the latest information.
The service is looking in particular at the flight suits, worn in combination with the pressure vests, by F-22 pilots at Joint Base Elmendorf-Richardson in Alaska and at Joint Base Langley-Eustis in Virginia, according to the official, who spoke on condition of anonymity because the investigation is being handled in private.
The official said investigators suspect the combinations may be restricting a pilot's ability to expand his chest and take a full breath.
The Alaska-based pilots wear an arctic survival suit intended to protect them after an ejection over cold terrain. Those based in Virginia wear anti-exposure suits as protection after an ejection over cold water. While similar to a wet suit, it doesn't fit as tightly.
The pressure vest serves as protection against both G forces and a rapid decompression at high altitude.