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The Air Force has pinpointed several contributing factors that may be leading to oxygen problems in the F-22, but has yet to find a "smoking gun," a three-star general said Tuesday.
Lt. Gen. Herbert "Hawk" Carlisle said during an Arlington, Va., event that a Scientific Advisory Board study has failed to find a conclusive cause for problems in the Raptors' On-board Oxygen Generation Systems, or OBOGS. The service stood down its entire fleet of F-22s for four months last year after problems with the oxygen system led to more than a dozen cases of hypoxia, a lack of oxygen that can cause headaches, nausea or blackouts.
"We have looked at everything on that system at the nth degree, and the bottom line is that there's no smoking gun," said Carlisle, the service's deputy chief of staff for operations, plans and requirements.
Carlisle, speaking at a breakfast of the Air Force Association, later told reporters that one contributing factor is leaks in the cooling system, although investigators could not determine how materials in the cooling system leaked into OBOGS. Another potential cause may be an interaction between contaminants and the materials in OBOGS that the service has yet to uncover.
The Air Force has taken several steps to prevent hypoxia since problems in the F-22 were discovered. Air Combat Command http://www.airforcetimes.com/news/2011/09/airforce-f22-grounding-end-this-week-091911w/">developed a plan that allows the 160 twin-engine fighters to fly above 50,000 feet — the Raptor normally flies at 60,000 feet — after an extensive inspection of every aircraft's life support systems.
Carlisle also said the Air Force is considering adding backup oxygen systems to its F-22s and continues to collect data from the aircraft to try and determine the malfunctions in OBOGS.