The Air Force granted a flight waiver to move F-22’s out of the path of Hurricane Irene, but the planes have been grounded off and on for the last five months while investigators try to figure out what’s wrong with the onboard oxygen generating system (OBOGS). Today they announced a delay in the scientific advisory board’s report until later in the winter.
More than 20 F-22 pilots have reported hypoxia-like symptoms. From Defense News:
Toxins found in pilots’ blood include oil fumes, residue from burned polyalphaolefin (PAO) anti-freeze, and, in one case, propane. Carbon monoxide, which leaves the blood quickly, is also suspected.
“There is a lot of nasty stuff getting pumped into the pilots’ bloodstream through what they’re breathing from that OBOGS [On-Board Oxygen Generation System]. That’s fact,” one former F-22 pilot said. “How bad it is, what type it is, exactly how much of it, how long – all these things have not been answered.”
The blood tests were performed after each of the 14 incidents in which pilots reported various cognitive dysfunctions and other symptoms of hypoxia. One couldn’t remember how to change radio frequencies. Another scraped trees on his final approach to the runway – and later could not recall the incident.
I’m sure the investigators have looked at the possibility of contaminated zeolite in the filter system. ISS had a problem with silicone outgassing in the system interfering with the zeolite doing its job of scrubbing the air. The problem was solved with a good bakeout in vacuum prior to flight.
I feel sorry for the pilots being stuck in the simulators for months, and I hope they get the OBOGS straightened out soon.