Forum: General F-22A Raptor forum

I'm pretty much seeing that this whole thing is based off of the fact that the F-22 does high altitude violent maneuvers? After Capt. Haney's crash, all F-22 flights were restricted below 25,000 ft. However, there were still plenty more incidents (including the pilot who hit a few trees on approach for his landing), after this flight level restriction. While it might have some affect on the OBOGS system, it's not the root cause.

I can't really understand what the guy in the video is saying, though so I'm just assuming this is what he's talking about.

I'm pretty much seeing that this whole thing is based off of the fact that the F-22 does high altitude violent maneuvers? After Capt. Haney's crash, all F-22 flights were restricted below 25,000 ft. However, there were still plenty more incidents (including the pilot who hit a few trees on approach for his landing), after this flight level restriction. While it might have some affect on the OBOGS system, it's not the root cause.

I can't really understand what the guy in the video is saying, though so I'm just assuming this is what he's talking about.

causes of F-22 oxygen problem have been found JameLi1986
http://www.defencetalk.com/forums/air-f ... und-11978/

"Published on May 29, 2012 by orion198606
causes of F-22 oxygen problem is discovered"

Thats just it, operational F-22 pilots don't currently wear full pressure suits. Neither do operational fleet F/A-18 pilots. That said, even the U-2/SR-71 pilots are not immune from decompression sickness (DCS). A F-22 pilot does not breath 100% oxygen during pre-flight or during all phases of the flight, so could (theoretically) be at a higher risk of DCS. A full pressure suit isn't a 'magic' solution because it all depends on the suit design. A higher internal pressure restricts movement but requires less pre-breathing. This was readily apparent on the ISS where crew had both Russian & American suits for spacewalks. The Russians had lower pressure suits, and were easier to work in.

As for the warning mechanism, I haven't heard of a OBOGS outflow leak occurring in a F-22 during flight to know for sure how the system would handle it. The F-22 Panel Mounted BRAG system is more advanced than the F/A-18 "chest" mounted regulator. The F/A-18 does not warn a pilot of a malfunctioning regulator with avionics.

The F/A-18 uses a Cobham OBOGS unit, whereas the F-22 has a Honeywell OBOGS. The F-15E Strike Eagle uses a Cobham OBOGS unit as well. The thing that is interesting is that the F-15E can fly high-altitude/high-G profiles when not heavily loaded down with stores, and has done so without 'physiological incidents' matching the F-22 pilot issues.

The problem is that they are not getting enough of a pattern to say if a pilot flies this profile in a F-22 that they'll duplicate the issue.

I think part of the issue with the Combat Edge flight suit is that it restricts breathing, especially at high altitudes, but not in a way that results in an immediate decrease in blood oxygen saturation. It is possible to have an increase in exhale CO2 without the noticeable decrease in O2 stats when breathing 100% oxygen. The Combat Edge system requires different techniques at high altitude/high-G profiles, which is not demonstrated during standard centrifuge AGSM training. Monitoring pilot respiration/exhale stats would give a clearer picture of a physiological cause.

Thanks for the very useful post!

Right now I believe in 2 possible causes:

1. The high altitude low cabin pressure + pure oxygen + high G maneuver = / Atelectasis This have 70% possibility

2. The high altitude low air speed cause the OBOGS to malfunction. This have 30% possibility

You say that F-15 also do high G maneuver at high altitude. That's a puzzling facts. Maybe the F-22 pilots do maneuver more frequent and more violent. I guess at high altitude(30000 feet+) the F-15 can't go beyond 6 G at most. This is my experience in combat SIMS
Any way we will wait and see the final report.
Thanks again for your profession information.