WASHINGTON (AP) - Defense Secretary Leon Panetta has approved an Air Force plan to begin lifting flight restrictions on the F-22 stealth fighter jet, following the ongoing correction of oxygen deficit problems that grounded and restricted the fleet for months.
Pentagon press secretary George Little said Tuesday that the Pentagon has "very high confidence that we've identified the issue" with the mysterious oxygen depletion problem that caused some F-22 pilots to feel dizzy and experience other symptoms of hypoxia. The Air Force now believes that a key problem was a valve in the pilots' pressure vest that caused it to inflate and remain inflated, triggering breathing problems.
In mid-May, Panetta ordered that F-22 flights remain "within proximity of potential landing locations" so pilots could land quickly if they experienced a lack of oxygen.
As of Tuesday, after a briefing from Air Forces leaders on Friday, Panetta has given the Air Force the green light to begin easing the restrictions, as changes are made to the fighter's oxygen system. The Air Force is replacing the valve and increasing the volume of air flowing to the pilots by removing a filter that was installed to check for contaminants in the system.
Little said Panetta also authorized the deployment of a squadron of F-22s to Kadena Air Base in Japan. He said that the jets will fly to the base under altitude restrictions, but after that the Air Force will begin resuming most longer-duration flights. The precautions for the Japan flight, said Little, are part of the measured approach the Air Force is taking to gradually return to normal flights.
Over time, the Air Force also plans to install a new backup emergency oxygen system, add sensors and put in an improved pilot oxygen center.
Once the changes are complete, the Air Force will seek approval to remove the flight restrictions that limit it from flying at high altitudes.
"The secretary believes that pilot safety is paramount. The gradual lifting of restrictions will enable the Air Force to resume normal F-22 operations over time, while ensuring the safety of the incredible airmen who fly this critical aircraft," said Little.
Little said he does not know the exact timeline for the return to normal operations. He noted that the flights to Japan will be at lower altitudes so that the vests would not have to be used.
Gen. Norton Schwartz, Air Force Chief of Staff, told Pentagon reporters that extensive testing has concluded that the problem was the amount of oxygen the pilots were getting, not the quality of the oxygen. And he said that the Air Force will modify and test the modified equipment "under the most demanding conditions," over the coming months and then will go back to Panetta for final approval to lift the flight restrictions.
The problem came to light when pilots complained publicly about the oxygen depletion, prompting Panetta to order the flight limits.
The F-22, manufactured by Lockheed Martin, is the Air Force's most-prized stealth fighter. It was built to evade radar and is capable of flying at faster-than-sound speeds without using afterburners.
Asked why the problem was not discovered during its lengthy testing and development, Schwartz acknowledged, "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.
So, Schwartz said the lesson is that the Air Force needs to pay better attention to the "man-machine interface" of its aircraft.