The US Air Force will not punish two F-22 Raptor pilots who publicly spoke out about problems with the Lockheed Martin-built aircraft's oxygen system, a senior service official tells Congress. Moreover, the USAF is getting close to solving the mystery behinds a series of hypoxia-like events that have plagued the Raptor fleet.

"We have some recent data that we are starting to believe we are coming to closure on that root cause," says Lt Gen Janet Wolfenbarger, military deputy to the USAF acquisitions chief. "We are realizing that we operate this aircraft differently than we operate any of our other fighter aircraft."

The Raptor flies higher than other fighters and also manoeuvers at high G-forces at those extreme altitudes, she says.

Lockheed Martin F-22 Raptor 

 ©US Air Force

Under USAF regulations, the Boeing F-15 Eagles and Lockheed F-16 Fighting Falcons are limited to 50,000 ft-though they rarely operate that high up. The F-22 routinely operates above 50,000 ft up to an operational ceiling of 60,000 ft. Raptor pilots receive a waiver to fly above the 50,000 ft mark-their Combat Edge anti-g ensemble is ostensibly considered to be a partial pressure suit.

60,000 ft is the limit due to the Armstrong Line, which sits at about 62,000 ft to 63,000 ft. At altitudes above the Armstrong Line the atmospheric pressure so low that water will boil at human body temperature--37 °C (98.6 °F).

The USAF has looked at hundreds of potential root causes of the problem, but the two most likely culprits are either some sort of contaminant or a problem with the oxygen flow to the pilot, Wolfenbarger says.

She insists that the Raptor is safe to fly. There have been 11 hypoxia-like incidents since the F-22 starting flying again in September, which is less than 0.1% of sorties.

Wolfenbarger says that Virginia Air National Guard pilots Captain Josh Wilson and Major Jeremy Gordon will be protected under US whistle-blower protection statues.

"My understanding is that the chief [of staff Gen Norton Schwartz] and secretary of the air force [Michael Donley] have issued direction that these individuals are protected," she says.

Meanwhile the USAF has agreed to consider future F-22 upgrades starting with Increment 3.2B as separate procurements from the acquisition of the aircraft themselves, Wolfenbarger says. That was done at the behest of the Government Accountability Office, which says those upgrades will cost $9.7 billion plus another $2 billion for airframe reliability modifications.

The USAF though has started to transition aircraft sustainment into a new joint military-contractor effort, which should save the service over $1 billion, she says.

Source: Flight International