Air Force leaders believe a faulty valve in a flight vest caused several previously unexplained incidents of hypoxia-like symptoms in F-22 Raptor pilots, and Defense Secretary Leon Panetta has approved a plan to gradually remove the restrictions he placed on the planes in May, Pentagon spokesman George Little said Tuesday.
“The Air Force is confident the root cause of the issue is the supply of oxygen delivered to pilots, not the quality of oxygen delivered to pilots,” Little said.
A valve in the vest the pilots wear at high altitude was causing the vest to inflate or deflate at inappropriate times, Little said. The vests, which are required above 44,000 feet to protect pilots in case of an accidental rapid decompression of the cockpit, have been suspended from F-22 flights since June. The valves will all be replaced and the Air Force will brief Panetta on the modifications before the planes return to normal duty, he said.
The Air Force will also increase the volume of air the pilots get by removing a charcoal filter that had been installed to determine whether the air supply was contaminated.
The Air Force grounded the F-22s last May after at least 14 incidents in which pilots experienced symptoms suggesting a lack of oxygen — including headaches, nausea, fatigue and difficulty concentrating. In March, an Air Force advisory panel could not discern the cause of the problem but felt strongly that the oxygen system was safe.
Air Force Chief of Staff Gen. Norton Schwartz said the unprecedented airborne capabilities of the F-22, including its extreme maneuverability at high altitude, caught the Air Force off guard.
“There were aspects of this that, physiologically for the aviator, weren’t well understood,” he said, later adding, “We missed some things, bottom line.”
On May 15, Panetta ordered the Air Force to keep all F-22 close to potential landing strips so they would be able to land quickly if problems arose.
The Air Force is still working on some safety improvements for the supersonic fighter, including a cockpit-mounted oxygen sensor and an improved pilot oxygen sensor, but other changes, such as a better-designed handle to activate the emergency oxygen system, have already been completed.
Schwartz said Tuesday that the precautionary steps, including altitude limits and requirements that F-22s stay remain closer to bases, have “minimized, perhaps not eliminated the risks, until the modifications are in place.”
The process to remove flight restrictions will begin immediately, Little said. A squadron of the supersonic fighters will deploy to Kadena Air Base in Japan “at any moment,” though the planes will be under altitude restrictions and will stay close to land during the trip, Little said.
While some questioned the timing of the deployment – in the midst of Japanese protests over the arrival of MV-22 Ospreys there – Schwartz said the move makes sense.
“There’s an operational requirement, and the birds are ready to go,” he said.