The Air Force will begin testing a new valve on pressurized vests worn by F-22 pilots. (Master Sgt. Jeremy Lock / U.S. Air Force)
A faulty valve on the pressurized vests worn by F-22 pilots will be replaced by the end of the year, a move aimed at solving pilots’ complaints of nausea and dizziness while flying the stealth fighter.
The valve connects the plane’s onboard oxygen supply to a tube that inflates the vest, protecting pilots from high-G forces. But a flaw in the valve caused the vests to be constantly inflated, even at lower altitudes when they weren’t needed, said Maj. Gen. Charles Lyon, the director of operations for Air Combat Command. The continuous pressure on the pilots’ chests caused symptoms of oxygen deficiency, or hypoxia.
“It 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,” Lyon said at a Pentagon briefing Tuesday.
Within a month, the Air Force will begin testing a new valve that will provide more tension and will restrict the airflow to the pressure vest until needed, he said.
The F-22s oxygen problems forced the Air Force to ground the entire fleet for four months last year. The planes returned to flight in September, but more complaints from pilots followed. On May 15, Defense Secretary Leon Panetta ordered the planes to fly at low altitude and within a safe landing distance of runways until the cause of the problem was identified.
Pilots were directed to stop wearing the pressurized vests in June, as investigative teams searched for clues.
Last week, a Pentagon spokesman announced that the valve on the vest was at least partly to blame. Within days, the Air Force deployed 12 Raptors of the 1st Fighter Wing at Joint Base Langley-Eustis, Va., to Kadena Air Base, Japan. The pilots stayed close to landing strips along the way, including stops at Joint Base Elmendorf-Richardson, Alaska, and Joint Base Pearl Harbor-Hickam, Hawaii, Lyon said.
“I have high confidence that we have eliminated the major contributing factors,” he said.
The Air Force has been under intense pressure to solve the F-22 problem, which first came to light after the November 2010 crash that killed Capt. Jeff Haney near Joint Base Elmendorf-Richardson. An accident investigation board found that Haney did not activate theF-22’s emergency oxygen system quickly enough or recover from a dive as he struggled to breathe. Air Force Chief of Staff Gen. Norton Schwartz has said Haney faced a “complex emergency.”
Lyon said there is no evidence that Haney’s crash was connected to the faulty valve now being replaced.
The Air Force first used pressurized vests in 1992, after years of testing. The vests worn by F-15 and F-16 pilots received a low-pressure supply of oxygen that would increase only in the event of a rapid decompression to protect the pilots’ lungs. But by the mid-2000s, the Air Force decided they were no longer needed in F-15s and F-16s. The vests were used in F-22s because they provided the pressure needed to help pilots breathe while flying at higher altitudes and under greater G forces, Lyon said.
Late last year, an Air Force Scientific Advisory Board investigation into the F-22 found that testing of the vest was “rudimentary” and didn’t identify the excessive restriction. F-22 pilots, when told of the faulty vest, said that they hadn’t noticed it was causing a problem, Lyon said.
F-22 pilots have flown 8,000 sorties and logged 10,000 flight hours without incident since March 8, when the last unexplained case of hypoxia was reported by a pilot, Lyon said.
Pilots will continue to take precautions, but changing the valve should lower the number of hypoxia incidents, he said.
“There will be physiological incidents in the future, in the F-22 and in other aircraft. That goes with the territory of high-performance fighter aircraft and fighter operations,” he said.