The Air Force believes it has found the source of pilots’ breathing problems in its F-22 Raptors and has lifted most of the flight restrictions on the jets, the Pentagon said Tuesday.
The easing of restrictions for long-duration flights for deployments, aircraft deliveries and repositioning of the aircraft will allow the Hawaii Air National Guard to start receiving the final six of its 20 Raptors — a delivery that had been delayed by the ongoing oxygen-supply problems.
The Air Force determined that a faulty valve caused an upper part of a pressure suit used at high altitudes to remain inflated when it should have deflated, causing pressure on the chest and breathing problems, the Pentagon said.
Additionally, the Air Force removed a canister filter from the oxygen delivery system that restricted airflow, and is making other improvements to delivery hoses.
High-altitude flights are still restricted. The Pentagon said it was authorizing the deployment of a squadron of F-22s to Kadena Air Base in Japan, but it will not involve the Hawaii Air Guard jets, an official said.
The Air Force kept the stealth jets flying in recent months as it continued to examine the cause of an increasing number of hypoxia incidents, or pilots not getting enough oxygen.
"With any aircraft — whether it’s the F-22 or the F-16 (or) a helicopter … we can never take the risk to zero," Pentagon spokesman George Little said Tuesday. "But we have an obligation to our troops and our airmen to make whatever equipment they are using as safe as possible, and that’s what we think we’re doing here."
A Hawaii Air Guard F-22 Raptor pilot declared an "in-flight emergency" July 6 after experiencing momentary dizziness, but landed safely at Joint Base Pearl Harbor-Hickam.
It was the first reported case of hypoxialike symptoms experienced by a Hawaii-based pilot, the Hawaii National Guard said.
The Air Force said the pilot experienced an in-flight oxygen system malfunction on a routine training sortie, and the problem was categorized as a physiological "cause known" event — rather than part of the series of problems that were unexplained until the Pentagon’s announcement Tuesday.
The F-22, built by Lockheed Martin, is the Air Force’s most prized stealth fighter. It was built to evade radar and is capable of flying at supersonic speed without using afterburners.
Air Force Chief of Staff Gen. Norton Schwartz, when asked why the problem was not discovered during its testing and development, said, "We missed some things, bottom line."
He said that the early testing did not reveal the shortcomings, and noted that some physiology and engineering expertise in the Air Force has diminished over the years.
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The Associated Press contributed to this report.
