The Air Force ordered immediate inspections this week of the backup oxygen units fielded on F-22 Raptor as it continues to grapple with oxygen supply issues behind groundings of the advanced fighter jets.
The inspections are focused on the Emergency Oxygen System (EOS), which was designed for use as a backup to the Onboard Oxygen Generation System (OBOGS).
The Air Force has been examining the oxygen supply systems after reports of pilots experiencing hypoxia or compression sickness following training sorties.
The service grounded the Lockheed Martin [LMT]-built fleet of 165 planes in May. They were briefly grounded again in October after returning to flight a month earlier.
Air Combat Command said the EOS has been needed on less than one percent of flights since the F-22s returned to the air and there were a small number of performance anomalies. Those cases were analyzed and corrected, the command said.
“This inspection has been implemented simply as a prudent step to ensure the full functionality of the EOS given increased usage under current operating procedures,” the command said.
“The EOS is a self-contained backup system. It is not linked to other aircraft systems, nor has it caused any hypoxia-like incidents,” the command added.
Air Combat Command said it expected the inspections to be complete within a week, and that sorties will continue to be flown on a reduced basis but only after the aircraft have undergone the inspection.
“Since the F-22 fleet returned to flying status in September 2011 we have adapted procedures to use the EOS as a precautionary measure to further protect pilots when they receive indications that physiological incidents may occur,” the command said.
The OBOGS system was under investigation following an F-22 crash in Alaska in November 2010 that left the pilot dead. Senior Air Force officials have since said the system was not at fault for the accident.