After five oxygen deprivation incidents, the US Air Force has temporarily canceled Lockheed Martin F-35A flying operations at Luke Air Force Base, Arizona.
Since 2 May, five F-35A pilots at Luke have reported “hypoxia-like symptoms,” said the USAF on 9 June.
The crews experienced a range of symptoms, from slight dizziness and disorientation to tingling and coldness in their extremities, but were trained to recognise the problems and landed safely using the aircraft’s backup oxygen system, says a spokeswoman for Luke AFB. Flight operations will resume 12 June, she says.
Fifty-five F-35As are stationed at Luke AFB, but the hypoxia issue only applies to 48 of those aircraft; seven aircraft flying at Mountain Home Air Base, Idaho for training this week returned to Luke on 9 June.
The F-35 Joint Programme Office had stood up an action team weeks ago to probe the oxygen issue, but after the fifth incident on 8 June, Luke AFB took the dramatic step of suspending flights.
“We have no idea what’s causing it,” the spokeswoman says. “There's been no testing across the board, we’re going to dig through the data to find some trends.”
The USAF does not yet know if the F-35s at Luke come from the same production lot, but the service is focusing on that aspect today, she adds.
The hypoxia incident appears to be isolated to Luke AFB and will not affect the F-35A’s appearance at the Paris air show, Lockheed spokesman says. The aircraft pair for the show will fly from Hill AFB, Utah and their test pilots have not experienced issues, says Lockheed.
Officials at the 56th Fighter Wing will tell US and international pilots of the conventional take-off and landing A-model to increase their awareness of hypoxia symptoms and crews will be briefed on successful actions taken in past incidents to recover the aircraft, says the USAF.
The F-35A grounding does not mark the first time the service has dealt with oxygen issues. In 2013, the USAF returned the F-22 to normal flight operations following a series of physiological incidents resembling hypoxia. The F-35 and F-22 both use an on-board oxygen generation system supplied by Honeywell.
Meanwhile, the US Navy continues its own battle against hypoxia. After the service lifted the temporary grounding of its T-45 trainer aircraft in April, the Goshawks are now grounded indefinitely. Only instructor pilots are allowed to fly the T-45 using ambient air, which restricts flying operations to a 5,000ft altitude and 2g manoeuvres. Vice Adm Paul Grosklags, commander of Naval Air Systems Command, told members of Congress during a 7 June hearing that the navy was examining options to get the T-45 back in the air.