After ordering a stand-down of all F-22 Raptors on May 3, the US Air Force is now examining other jets for similar faults with their onboard oxygen generating systems. Many US Air Force aircraft share the same oxygen equipment.
A deadly F-22 crash on November 16 last year prompted the Air Force to begin investigating the On-Board Oxygen Generation Systems (OBOGS) aboard the F-22, F-35 Lightning II Joint Strike Fighter (JSF) and other tactical aircraft and trainers. The service last week stood down all F-22s after a spike in incidents potentially related to hypoxia.
“No other airframes have been stood down due to this investigation; however, a parallel investigation is taking place on the on-board oxygen generation systems on the A-10, F-15E, F-16, F-35 and T-6 aircraft,” said Captain Jennifer Ferrau, an Air Force spokeswoman for Air Combat Command (ACC).
Since January, Raptors have been kept at altitudes below 25 000 feet during the ongoing investigation in order to lessen the risk in case their oxygen systems malfunctioned. If the OBOGS failed at 25 000 feet pilots would have time to recover to lower altitudes where there is enough oxygen in the atmosphere. This is not the case when the aircraft flies at its 50 000 feet ceiling, as the pilot would only have ten seconds of consciousness.
As the Air Force could not say when the F-22 would be flying again, the entire fleet is standing down indefinitely.
“We are still working to pinpoint the exact nature of the problem. It is premature to definitively link the current issues to the OBOGS system,” Ferrau said. “The safety of our airmen is paramount and we will take the necessary time to ensure we perform a thorough investigation.”
There have been nine suspected cases of hypoxia during F-22 operations since mid-2008, and recently there have been 14 recorded OBOGS incidents.
“Over the last week, we have experienced five additional F-22 ‘Physiological-Hypoxia Like’ events across the Air Force, which led Commander of Air Combat Command to establish the current F-22 stand-down,” Ferrau said. Ferrau reports “increased frequency of pilot reported physiological incidents such as hypoxia and decompression sickness.”
F-22 manufacturer Lockheed Martin has deployed a team to assist the Air Force during its OBOGS investigation, according to company spokesperson Stephanie Stinn.