June 20, 2012:
The U.S. Air Force has admitted that its rate of "pilot air supply" incidents for its 187 F-22 fighters has reached the rate of 26 per 100,000 flight hours. For most other aircraft, the rate is closer to 2-3 incidents per 100,000 hours. Yes, all aircraft have occasional problems with their air supply but nothing like what the F-22 is going through.
The F-22 problem has been around for over two years and in the news, to the great embarrassment of the air force commanders, for over a year. Finding a solution has turned into a nightmare because it has proved impossible, so far, to discover exactly what is causing the air supply problem. In addition to all the bad publicity, F-22 pilots are reluctant to fly their aircraft. In short, pilot moral is not very good.
The F-22s comprise the most powerful component of the air force's air combat capability and the brass are increasingly desperate to find out exactly what is wrong and fix it. The air force recently received the last of 187 F-22s that will be built. Production was limited because these aircraft were too expensive. It's very embarrassing that their safety should be threatened by something so basic as the pilot air supply.
The air force woes began when it appeared that the F-22 might be having a problem with its OBOG (OnBoard Oxygen Generating) system. OBOGs have been around for over half a century. It's only in the last two decades that OBOGs have become compact, cheap, and reliable enough to replace the older compressed gases or LOX (liquid oxygen) as a source of breathable air for high flying aircrew. Each aircraft, especially the F-22 and F-35, gets an OBOG tweaked for space, weight, or other conditions specific to that warplane design. It's this custom design that was also closely studied, to find out how the toxins got in.
One problem is that aircraft have been staying in the air longer (because of in-flight refueling) and carrying enough compressed oxygen has become untenable, requiring OBOGs to solve the problem. Since the 1990s, most American military aircraft have replaced older oxygen systems with OBOGs. Most Western nations, and Russia, have followed, at least with their latest model aircraft. Most OBOG systems work by using a chemical reaction to remove carbon dioxide from the air taken in to the OBOG and then sending out air with the proper amount of oxygen to the aircrew. The F-22 was designed to fly long distances and spend long periods of time in the air. Thus an OBOG is mandatory.