Fourteen F-22 Raptor jets have been put on stand-down at Nellis Air Force Base with the rest of the nation’s fleet while investigators probe potential oxygen system malfunctions, Air Force officials said Friday.
Gen. William Fraser, commander of Air Combat Command, ordered the stand-down on Tuesday, according to a statement from headquarters at Langley Air Force Base, Va.
“The stand-down provides Air Force officials the opportunity to investigate the reports and ensure crews are able to safely accomplish their missions,” the statement said.
The stand-down of the fleet of 158 jets was prompted by “hypoxialike” symptoms reported by some of the fleet’s pilots, said Air Combat Command spokeswoman Master Sgt. Pamela Anderson. Hypoxia is when the body receives too little oxygen.
As opposed to grounding the fleet, the stand-down is considered precautionary and voluntary and is being observed at Nellis and a handful of other bases .
Nellis spokesman Chuck Ramey said 14 Raptors are assigned to the base, in the north Las Vegas Valley. They are flown by the 422nd Test and Evaluation Squadron and the 433rd Weapons Squadron.
Since January, the Raptor fleet has been restricted from flying above 25,000 feet because of concerns with the plane’s oxygen supply system.
An F-22 pilot, Capt. Jeffrey Haney, was killed in Alaska in November when he lost control of his jet during a training exercise and never ejected. Because the cause of that crash hasn’t been determined, Anderson cautioned against linking it to Fraser’s stand-down order.
But she said some pilots have reported physiological events similar to hypoxia, and that was the reason for the general’s decision for the stand-down.
Anderson said she did not know how long the stand-down would last.
F-22s were grounded for two weeks after one crashed at Nellis Air Force Base on Dec. 20, 2004. They were cleared to fly again after a review. The pilot, Maj. Robert Garland, successfully ejected.
Investigators determined that a power interruption of less than a second led to a flight-control software glitch that caused the Nellis jet to crash on takeoff. The interruption occurred when the F-22’s engines were shut down for maintenance and power to the aircraft was being supplied by an auxiliary ground unit.
The radar-evading F-22s each cost roughly $140 million. The warplanes can carry air-to-air missiles and are capable of ground attack too.
With its stealth design, the F-22 can evade radar and has advanced engines that allow it to fly at faster-than-sound speeds without using afterburners.
Contact reporter Keith Rogers at firstname.lastname@example.org or 702-383-0308. The Associated Press contributed to this report.