​F-22 Pilot Chokes On Oxygen System Causing Hypoxia

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July 13, 2012

An F-22 Raptor pilot had suffered an oxygen deficit last week and now Air Force investigators are looking into whether engine startup procedures for jets at Joint Base Elmendorf-Richardson could be responsible for the hypoxia.

F-22 Pilot Oxygen

According to the Air Force Times, most of the hypoxia incidents have occurred at JBER, where F-22s are often started up inside hangars due to harsh weather outside. Investigators believe carbon monoxide generated by the Raptors’ own jet engines could be getting ingested back into the engines’ bleed air intakes. Those intakes supply the on-board oxygen generation system, or OBOGS, which provides oxygen to the pilot.

JBER officials had no comment on the issue Thursday.

The Air Force barred the 158-aircraft Raptor fleet from flying above 25,000 feet in January after receiving nine reports of symptoms similar to hypoxia, a form of oxygen deprivation. The fleet later received a May stand-down order to investigate OBOGS concerns, following five more reports of similar symptoms within a week.

Air Force Capt. Jeffrey Haney, 31, was killed on impact Nov. 16 when his 525th Fighter Squadron F-22 lost contact with air traffic control and a partner aircraft, then crashed during a training exercise about 100 miles north of Anchorage.

The Air Force said its investigation of the November crash was incomplete, and it had no conclusive evidence to connect Haney’s death to the OBOGS issue.

Officials say the F-22’s bleed air intake positions are fairly common for jet aircraft, and that no immediate fix is in sight. Aviation-safety expert Hans Weber told the Times, however, that simple solutions might include starting Raptors’ engines outside hangars or delaying startup of the oxygen system until leaving the hangar.

Failing that, Weber said, tackling the problem might require adding CO scrubbers to the plane’s oxygen system.

The Navy experienced similar problems with its F/A-18 Hornet fighters during carrier operations from 2002 to 2009, with 64 hypoxia cases reported — including two involving pilot deaths. An investigation suggested that the problem was caused by carbon monoxide entering the oxygen system while pilots idled behind other aircraft waiting to take off, and the Hornets were modified to fix the problem.

No similar incidents have been reported in F/A-18s since the fix, according to the Navy.