Every year around 400 people die from accidental carbon monoxide poisoning in the U.S., often resulting from cars left running in closed garages. Now we can possibly add one U.S. Air Force stealth fighter pilot to the list of garage fatalities.

CO poisoning is the latest suspect in a rash of pilot blackouts and other incidents involving the $300-million, radar-evading F-22 Raptor – including a fatal crash in November.

In May, the Air Force grounded all 150 frontline F-22s at their bases in Virginia, Alaska and Hawaii, pending investigation into the incidents. "The safety of our aircrews is paramount," said Maj. Chad Steffey, an Air Force spokesman. The grounding effectively cut the Air Force's dogfighting fleet in half, at a time when Russia and China are steadily developing their own advanced fighters.

Raptor pilots had been reporting memory loss and disorientation during flight, pointing to a shortage of breathable air inside the cockpit. In July, the Air Force narrowed its focus to the F-22's On-Board Oxygen-Generation System, or "OBOGS," a filter built by Honeywell that removes nitrogen from thin, high-altitude air.

Oddly, no other airplanes fitted with similar, even identical, oxygen systems are having any problems. That led investigators to consider other possible causes. Noting that most of the blackouts happened in Alaska, as did November's fatal crash, the Air Force sleuths took a hard look at procedures at Elmendorf Air Force Base, the Alaskan Raptors' main roost.

They found that, to keep out of the Alaska cold, airmen at Elmendorf routinely started up their F-22s' engines while the jets were still parked inside sealed hangars. In essence, the Raptors were like cars dangerously left running in closed garages. "Investigators suspect that exhaust gases are getting trapped in the building and subsequently sucked back into the engines, where they enter the bleed air intakes that supply the OBOGS," Defense News' Dave Majumdar wrote.

If that's the case, ending the Raptor grounding is as easy as opening up those hangar doors, although engineers might also look at better sealing inside the airframe.

Don't celebrate quite yet. The Air Force hasn't ruled for certain that exhaust is causing the blackouts. The OBOGS itself, or something else, might still be to blame. But for the first time in three months, the investigation is gaining some traction.

Still, even if the flight ban ended today, it could take months for Raptor pilots to make up for 10 weeks without flight training.

Photo: Air Force

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