Oxygen Gernerator problems may go back to WWII

[tincansailor]

I hope this isn't an old topic. I was just reading a book about the USS Enterprise CV-6 in WWII. It said that during the Battle of Midway a U.S. Dive bomber pilot had his flying career ended by lung damage from an oxygen Rebreather system. Dick Best, who planted 2 bombs, on 2 missions, against 2 separate Japanese Carriers in the same day flew a 4 hour, high altitude mission on that amazing day, June 4, 1942.

On the night of the 4th he went to bed, but began coughing up blood. The chief medical officer in Pearl Harbor concluded that his "Oxygen Rebreather " had become over heated during his long flight. "The heat created gases that turned to caustic soda, activating latent TB."

I didn't know U.S. naval aviators used oxygen rebreathers in WWII. I used chemical oxygen generators as damage control equipment when I was in the in the navy. The chemical canister became very hot, and had to be disposed of carefully. I don't know what this had to do with what happened to Dick Best, or if it has any relationship with the oxygen generation system problems with the F-22. Does anyone have any information on oxygen generators, or rebreathers in WWII, or if it has any relationship to the problems the F-22 experienced?

[35_aoa]

Don't know anything about said system, but I am guessing that it was different than OBOGS. As you are probably aware, OBOGS uses [insert number based on platform] stage bleed air from a turbine/jet engine, cycles it through a scrubber (i.e. "molecular sieve") and then on to the individual crew regulators for breathing. The big problem with OBOGS is that sieve failing over time, or in other cases, toxins getting through which weren't designed to be scrubbed out. And then you get into the larger issue of flying jets at high altitude with finicky ECS/cabin pressurization systems without wearing a pressure suit. The first leads to toxic hypoxia, the second is completely unrelated to OBOGS and leads to DCS but is often lumped into "physiological episodes" or mishaps related to that factor.

[neurotech]

Don't know anything about said system, but I am guessing that it was different than OBOGS. As you are probably aware, OBOGS uses [insert number based on platform] stage bleed air from a turbine/jet engine, cycles it through a scrubber (i.e. "molecular sieve") and then on to the individual crew regulators for breathing. The big problem with OBOGS is that sieve failing over time, or in other cases, toxins getting through which weren't designed to be scrubbed out. And then you get into the larger issue of flying jets at high altitude with finicky ECS/cabin pressurization systems without wearing a pressure suit. The first leads to toxic hypoxia, the second is completely unrelated to OBOGS and leads to DCS but is often lumped into "physiological episodes" or mishaps related to that factor.

Agree with your comments on OBOGS & DCS.

Despite what some people seem to suggest, the OBOGS & ECS in a F/A-18C/D/E/F is completely different to the F-22, even though they work on a similar principle ("molecular sieve" etc.). Some aviation physiologists were pretty confident the F-22 "physiological episodes" were not caused by OBOGS issues, and they were later proven correct.

One frustration with the "physiological episodes" is that there is little solid evidence of what actually happened. F-22 pilots do use SpO2 sensors, which will detect typical hypoxia, but not always detect toxic hypoxia. Even when they get the aircraft (F-22, F/A-18 etc.) back in one piece, there can be very little data from a physiological episode.

IMO F/A-18s should get more comprehensive environmental monitoring data recorders, to make investigating a lot easier. Hurry up and replace the sieve units would also help.

[popcorn]

Retrofitting an automatic emergency O2 backup system on the Raptor was money well spent.

[neurotech]

Retrofitting an automatic emergency O2 backup system on the Raptor was money well spent.

Yes, money well spent. There is a bunch of reasons that automatic emergency O2 backup is a good idea, that are unrelated to the OBOGS unit itself. Dual Bleed Air Leak is one of the failures that will shut the OBOGS down.

[35_aoa]

Don't know anything about said system, but I am guessing that it was different than OBOGS. As you are probably aware, OBOGS uses [insert number based on platform] stage bleed air from a turbine/jet engine, cycles it through a scrubber (i.e. "molecular sieve") and then on to the individual crew regulators for breathing. The big problem with OBOGS is that sieve failing over time, or in other cases, toxins getting through which weren't designed to be scrubbed out. And then you get into the larger issue of flying jets at high altitude with finicky ECS/cabin pressurization systems without wearing a pressure suit. The first leads to toxic hypoxia, the second is completely unrelated to OBOGS and leads to DCS but is often lumped into "physiological episodes" or mishaps related to that factor.

Agree with your comments on OBOGS & DCS.

Despite what some people seem to suggest, the OBOGS & ECS in a F/A-18C/D/E/F is completely different to the F-22, even though they work on a similar principle ("molecular sieve" etc.). Some aviation physiologists were pretty confident the F-22 "physiological episodes" were not caused by OBOGS issues, and they were later proven correct.

One frustration with the "physiological episodes" is that there is little solid evidence of what actually happened. F-22 pilots do use SpO2 sensors, which will detect typical hypoxia, but not always detect toxic hypoxia. Even when they get the aircraft (F-22, F/A-18 etc.) back in one piece, there can be very little data from a physiological episode.

IMO F/A-18s should get more comprehensive environmental monitoring data recorders, to make investigating a lot easier. Hurry up and replace the sieve units would also help.

Yeah, particularly with hypoxia events, time is of the essence assuming you land safely. If I'm not mistaken, medical needs to get you in within an hour of the event to properly read your blood. I've done that drill twice, both times were delayed due to outside factors……..first one being extended transit back home, second one being more of a possible DCS case (didn't actually resolve into one) after a rapid decompression at 40k+ ft, unfortunately when I put the gear down to land, I had planing link failure indications, and had to take a trap. Took almost an hour just to get towed off the runway due to runway/taxiway closures. Had to tell the wife that evening that if I started acting weird (weirder than normal at least ) or unusually angry, to get me in the car and to the hospital recompression chamber in Reno. Needless to say, she wasn't too psyched about my job that day.

As for other platforms, totally agree. The retrofitted F-15C/E fleet has not had anywhere close to the amount of problems the F/A-18 has had from what I understand. Strange because Mac Air built both, though apparently the OBOGS in the -15 is much newer tech. There were a lot of engineering assumptions made for the F/A-18 in the life support realm that were not accurate. One of them is that cockpit ambient air is not scrubbed in any meaningful way because the engineers (incorrectly) assumed that we would be wearing our O2 masks from engine start to shutdown. In combat in OEF/OIF, with upwards of 7-8 hour missions, LOX jets didn't even have the capacity to support that. OBOGS lets you, but most folks don't fly around for that amount of time in a low threat environment wearing the mask the entire time. Hence some of the "toxic" hypoxia events, though many more have been attributed to wearing the mask after an unannounced/undetected OBOGS failure.

[popcorn]

From the other thread we learn the actual scale of the problem plaguing the Hornet.
I'd be curious to see the numbers for the years leading up to 2010.


http://hrana.org/articles/2017/01/ea-18 ... explosion/

The Hornet fleet, Growler included, has been plagued with issues surrounding its environmental systems. The Super Hornet’s issues are supposedly related to its onboard oxygen generation system (OBOGS) that supplies air to the aircraft’s crew. The legacy Hornet’s issues, which have been less severe, are thought to be due to the jet’s cabin pressure system as it does not have an OBOGS and uses liquid oxygen instead. Between May 2010 and October 2015 there had been 297 documented physiological incidents of all types on Hornets, but most have to do with hypoxia (the lack of oxygen to the brain and its debilitating effects) or a total and sudden loss of airflow to the aircrew. None of the incidents involved a death or a crash of any sort, but still the problem is well known within the Hornet community.

[35_aoa]

FWIW, a lot of legacy jets (C/D) have OBOGS, and either came that way from the plant, or were retrofitted. My lot 13/14 legacy squadron had an all OBOGS flight line, and so did our sister squadron once they got rid of their A+'s. The same issues have occurred in legacy Hornets, T-45's, and to a lesser extent, AV-8B, all equipped with the same OBOGS from MacAir/Boeing.

[neurotech]

From the other thread we learn the actual scale of the problem plaguing the Hornet.
I'd be curious to see the numbers for the years leading up to 2010.


http://hrana.org/articles/2017/01/ea-18 ... explosion/

The Hornet fleet, Growler included, has been plagued with issues surrounding its environmental systems. The Super Hornet’s issues are supposedly related to its onboard oxygen generation system (OBOGS) that supplies air to the aircraft’s crew. The legacy Hornet’s issues, which have been less severe, are thought to be due to the jet’s cabin pressure system as it does not have an OBOGS and uses liquid oxygen instead. Between May 2010 and October 2015 there had been 297 documented physiological incidents of all types on Hornets, but most have to do with hypoxia (the lack of oxygen to the brain and its debilitating effects) or a total and sudden loss of airflow to the aircrew. None of the incidents involved a death or a crash of any sort, but still the problem is well known within the Hornet community.

Not all the physiological issues are caused by OBOGS. There are many other parts of the Environmental Control systems (ECS) that can create major issues for the crew if something goes wrong. The recent EA-18G had nothing to do with the OBOGS and a lot to do with the ECS. An outflow valve got blocked causing an overpressure event.

My understanding is that some of these physiological issues resulted in a some hard landings, maybe a few Class-C level mishaps.

[popcorn]

Another Navy jet with breathing issues. Pilots putting their foot down.
http://www.foxnews.com/politics/2017/04 ... ected.html

[jessmo111]

This is the same Hornet, that Boeing is pushing as the NAVAIR messiah?

[mixelflick]

This is the flip side of owning an all Hornet Navy. Sure, you get savings in the logistical chain. But the flip side of it is playing out now - ALL Hornets are said to have issues. Going to make it rather difficult to answer the call of duty, when (not if) that day comes.

If the Navy was still flying Tomcats/Bombcats, at least it would have a viable (and in some way superior) alternative..

[mor10]

Another Navy jet with breathing issues. Pilots putting their foot down.
http://www.foxnews.com/politics/2017/04 ... ected.html

This article is about the T-45, not the Hornet, just in case some here got confused.

[mor10]

This is the flip side of owning an all Hornet Navy. Sure, you get savings in the logistical chain. But the flip side of it is playing out now - ALL Hornets are said to have issues. Going to make it rather difficult to answer the call of duty, when (not if) that day comes.

If the Navy was still flying Tomcats/Bombcats, at least it would have a viable (and in some way superior) alternative..

As will be the case with an all F-35 fleet, or all M-L fleet, just to be the devils advocate. While I'm a fan of both the F-35 and the F-22, this is a potential issue to be aware of. The F-22 has already demonstrated this, with its own "oxygen" issues.