The F-22 fleet has been plagued by a mysterious air supply problem for more than a year. Strategy Page reports on what might be the solution:

The U.S. Air Force has concluded (for the moment) that the cause of the breathing problems F-22 pilots were having were caused by a defective valve on the special vests pilots wear to help them with their breathing in the low pressure of the F-22 cockpit. The vests are not being used until modifications can be made to fix the problem.

Earlier this year the vests came under suspicion because it appeared that they automatically inflated too much during high-g (gravitational force) maneuvers, making it difficult for pilots to breathe. This would be subtle, so that the pilot would not immediately notice a problem with breathing. Anything obvious would have been noticed when the vest was tested. Pilots have complained about a “strange feeling” when breathing with the vest during high-g turns but not in such a way that they connected it with the disorientation. Further examination discovered that the vest was indeed inflating when it should not have been, and causing breathing problems. The air force will make a few other tweaks to the pilot air supply system and quietly hope that the problem is indeed solved.

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Now the air force can drop a number of precautionary restrictions imposed over the last year. For example, pilots were forced to make flights at least 24 hours apart. In training, and combat, pilots would take their F-22s up two or more times a day. The theory was that the pressure vests and acceleration atelectasis would not be a problem if pilots have at least 24 hours to recover.

Despite the breathing problems the air force continued to fly its F-22s. The decision to keep flying was made because the air supply problems had not killed anyone yet and they were rare (once every 10,000 sorties). The 14 incidents that did occur were all cases of F-22 pilots apparently experiencing problems. The term “apparently” is appropriate because the pilots did not black out and a thorough check of the air supply system and the aircraft found nothing wrong.

Here’s the initial discussion of the problem from July last year. In September, the F-22s were cleared to fly again, but they were grounded again in October.

As if the F-22 hadn’t already had enough issues, there’s a new concern called the “Raptor cough” (acceleration atelectasis) showing up among F-22 pilots:

Increasingly desperate to find out what is causing its F-22 (“Raptor”) fighter pilots to get disoriented while in the air, the U.S. Air Force is now investigating what appears to be excessive coughing by F-22 pilots. It’s being called “Raptor Cough” and is actually a known condition (acceleration atelectasis) for pilots who have just completed a high speed maneuver. But it appears to be showing up more frequently among F-22 pilots. That may be the result of months of tension over the reliability and safety of the aircraft. The F-22 pilots are perplexed and a bit nervous about their expensive and highly capable jets.

The air force believes that something, as yet unknown, is getting into the pilot air supply and causing problems. Despite this, the air force continues flying its F-22s. The decision to keep flying was made because the air supply problems have not killed anyone yet and they are rare (once every 10,000 sorties).

The 14 incidents so far were all cases of F-22 pilots apparently experiencing problems. The term “apparently” is appropriate because the pilots did not black out and a thorough check of the air supply system and the aircraft found nothing wrong. There have been nearly 30 of these “dizziness or disorientation” incidents in the last four years, with only 14 of them serious enough to be called real incidents. Only one F-22 has been lost to an accident so far and, while that did involve an air supply issue, it was caused by pilot error, not equipment failure.

Strategy Page has an update on the F-22 and the ongoing investigation into air supply problems for the pilot:

The U.S. Air Force is admitting that it is having a problem with the pilot air supply on the F-22, a problem they have not been able to find the cause of. Despite this, the air force is going to continue flying its F-22s. The decision to keep flying was made because the air supply problems have not killed anyone yet and they are rare (once every 10,000 sorties.)

The 14 incidents so far were all cases of F-22 pilots apparently experiencing problems. The term “apparently” is appropriate because the pilots did not black out and a thorough check of the air supply system and the aircraft found nothing wrong. There have been nearly 30 of these “dizziness or disorientation” incidents in the last four years, with 14 of them serious enough to be called real incidents. Only one F-22 has been lost to an accident so far and, while that did involve an air supply issue, it was caused by pilot error, not equipment failure.

Meanwhile the air force is spending $7 million to install commercial oxygen status sensors in the air supply systems of its F-22 fighters. This is part of a year-long effort to find out what’s causing the air supply on F-22s to get contaminated and cause pilots to become disoriented or pass out. Twice in the past year the entire F-22 fleet was grounded because of the air supply problems. The first grounding lasted 140 days and ended last September. The second grounding lasted a week and ended five months ago. The 180 F-22s comprise the most powerful component of the air force’s air combat capability and the brass are eager to find out what is wrong.

After all the F-35 bashing around here lately, it’s only fair that we give equal time to the other hyper-expensive fighter, the F-22:

The U.S. Air Force is upgrading its F-22 fighters, at a cost of $39 million each. This is just the latest of several upgrades for the F-22, which entered service six years ago. Upgrading combat aircraft is common, and necessary. But the F-22 upgrades have been more expensive than previous aircraft. The F-22 is also more expensive to maintain. That costs $44,000 per flight hour, compared to $30,000 per hour for the older F-15 that the F-22 is replacing. The F-22 per-hour cost is nearly twice what it is for the F-16. While it requires 19 man hours of maintenance for each F-16 flight hour, the F-22 requires 34 hours. The manufacturer originally said it would be less than ten hours. Most of this additional F-22 expense (and man hours) is for special materials and labor needed to keep the aircraft invisible to radar.

The main problem is the radar absorbent material used on the aircraft. The B-2 had a similar problem, which was eventually brought under control. But even then, the B-2 cost more than twice as much to operate than the half century old B-52. The B-2 and F-22 use different types of radar absorbent materials, so many of the B-2 solutions will not work for the F-22. Some of the F-22 electronics were not as reliable as the air force expected.

[. . .]

In addition, the F-22 costs more than three times as much as the aircraft it was to replace. The air force wants to build more than 187, and has allies in Congress who want the jobs (and votes) continued production would generate. But the Department of Defense was reluctant to spend that kind of money, especially when there so many other programs seeking funds (like electronic warfare aircraft, UAVs and upgrades for F-15s and F-16s). Thus, two years ago, the Department of Defense decided to terminate F-22 production at 187 aircraft. This resulted in each aircraft costing (including development and production spending), $332 million. Just the production costs of the last F-22s built was $153.2 million. Added to the cost of the last few aircraft was a $147 million fee the Department of Defense agreed to pay if the production line was shut down. This goes to pay for shutting down facilities and terminating contracts with hundreds of supplies.

The F-22 is a superb aircraft, probably the most capable fighter in the world. But the development and manufacturing costs kept rising until it became too expensive for the media, voters and politicians. The air force was able to build it, but they couldn’t sell it to the people who paid the bills.

On the other hand, a bit of good news from last week: at least the F-22 is allowed to fly again.

The months-long grounding is over:

On September 21st, the U.S. Air Force will allow its F-22 fighters to fly again. The aircraft had been grounded for 140 days because of problems with the pilot’s oxygen system. The air force is not giving out many details on exactly what the problems is, although they say a report on the F-22 oxygen system will be out by the end of the year. Each F-22 will undergo a detailed inspection before it is cleared to fly. This may have something to do with earlier remarks about toxins somehow getting into the pilot’s air supply. The problem was always about something bad in the air supply. This has kept all 168 F-22s grounded since May. The only exception was a squadron based on the Virginia coast, that was given permission to fly out of the way of hurricane Karina. Those F-22s encountered no problems with their air supply.

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During the grounding, pilots and ground crews used simulators and (for the ground crews) maintenance exercises on the grounded aircraft to keep their skills sharp. In addition, everyone helped checking out a growing list of aircraft components in support of the search for the breathing problem). The air force was also under time pressure to fix the problem. That’s because after 210 days on the ground, aircrew have to undergo extensive retraining to regain combat flying status. This added a little more urgency to fixing the problem quickly. The grounding also left a dozen F-22s stranded at a training base, where they were for live weapons exercises. At least six new F-22s could not be delivered because of the grounding.