Oxygen concentrators

Morne

Morne

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Morne
I am guessing that the portable oxygen concentrators are not considered sufficient for the required supplemental oxygen to crew, right?

No need to discuss the economics of them versus cylinders, just an academic discussion.

Has anyone used one, even as a passenger, in a GA aircraft above 12,500'? If so, what sort of oxygen saturation improvement did you see?
 
I tried one, unscientifically, with a PoX. It was about equivalent to 1 L flow of O2 at 12,000 but was USELESS at 15,000. There just aren't enough molecules up there. to concentrate easily....
 
The military fighter jets use them up to 50,000ft but they are fed by the engine compressor stage to over 100psi.

José
 
Piloto said:
The military fighter jets use them up to 50,000ft but they are fed by the engine compressor stage to over 100psi.
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Not quite. That only pressurizes the cabin, but there are limits to max psi differential, and above a certain altitude where cabin altitude gets above 8000 or so, you're mask-on breathing O2 from the O2 system (usually supplied by a LOX bottle) via a diluter/demand pressure/mixture regulator. At 50,000, you are definitely mask-on in any military fighter jet, and the engine compresser bleed tap air is not going into your lungs.
 
Ron Levy said:
Not quite. That only pressurizes the cabin, but there are limits to max psi differential, and above a certain altitude where cabin altitude gets above 8000 or so, you're mask-on breathing O2 from the O2 system (usually supplied by a LOX bottle) via a diluter/demand pressure/mixture regulator. At 50,000, you are definitely mask-on in any military fighter jet, and the engine compresser bleed tap air is not going into your lungs.
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Even the F-22?
 
Old Geek said:
Even the F-22?
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Cabin pressure differential is a factor in combat survivability -- more cabin pressure means more vulnerability. While I don't have the exact specs, it's highly unlikely that the F-22 has the 13.1 psi cabin differential which would be necessary for an 8000 foot cabin altitude (allowing mask-off operation) at 50,000 MSL. To do so would require a ton of extra structure (literally), and weight on a fighter is too critical for that. The big technology change in that department on the F-22 is the use of an On-Board Oxygen Gas Generating System (OBOGGS) instead of LOX bottles to provide the O2 going into the pilot's mask, and it is in that OBOGGS where all the problems are occurring.
 
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Ron Levy said:
Cabin pressure differential is a factor in combat survivability -- more cabin pressure means more vulnerability. While I don't have the exact specs, it's highly unlikely that the F-22 has the 13.1 psi cabin differential which would be necessary for an 8000 foot cabin altitude (allowing mask-off operation) at 50,000 MSL. To do so would require a ton of extra structure (literally), and weight on a fighter is too critical for that. The big technology change in that department on the F-22 is the use of an On-Board Oxygen Gas Generating System (OBOGGS) instead of LOX bottles to provide the O2 going into the pilot's mask, and it is in that OBOGGS where all the problems are occurring.
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Seems like the pilot's are gonna have to wear masks up that high anyway, even if it's just to be able to remain conscious if pressurization is lost so I don't see much point in pumping the cabin pressure up that high. I'd think the ideal cabin altitude would be one were pressure breathing isn't required to maintain sufficient blood O2 saturation and IIRC that's between 25000 and 30000 ft. Wouldn't anything lower than that just reduce the amount of O2 required if you're already wearing a mask?
 
gismo said:
Seems like the pilot's are gonna have to wear masks up that high anyway, even if it's just to be able to remain conscious if pressurization is lost so I don't see much point in pumping the cabin pressure up that high.
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IIRC, the Air Force required masks on above 35,000 regardless of cabin altitude for just that reason. The FAA rules are similar:
(b) Pressurized cabin aircraft.
(1) No person may operate a civil aircraft of U.S. registry with a pressurized cabin--
(i) At flight altitudes above flight level 250 unless at least a 10-minute supply of supplemental oxygen, in addition to any oxygen required to satisfy paragraph (a) of this section, is available for each occupant of the aircraft for use in the event that a descent is necessitated by loss of cabin pressurization; and
(ii) At flight altitudes above flight level 350 unless one pilot at the controls of the airplane is wearing and using an oxygen mask that is secured and sealed and that either supplies oxygen at all times or automatically supplies oxygen whenever the cabin pressure altitude of the airplane exceeds 14,000 feet (MSL), except that the one pilot need not wear and use an oxygen mask while at or below flight level 410 if there are two pilots at the controls and each pilot has a quick-donning type of oxygen mask that can be placed on the face with one hand from the ready position within 5 seconds, supplying oxygen and properly secured and sealed.
(2) Notwithstanding paragraph (b)(1)(ii) of this section, if for any reason at any time it is necessary for one pilot to leave the controls of the aircraft when operating at flight altitudes above flight level 350, the remaining pilot at the controls shall put on and use an oxygen mask until the other pilot has returned to that crewmember's station.
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14 CFR 91.211
 
Ron Levy said:
The big technology change in that department on the F-22 is the use of an On-Board Oxygen Gas Generating System (OBOGGS) instead of LOX bottles to provide the O2 going into the pilot's mask, and it is in that OBOGGS where all the problems are occurring.
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Since you mentioned the F22 problems: I have been wondering why they can't just switch back to LOX bottles. It seems crazy to ground a $300M jet when an oxygen bottle could fix it.
 
[email protected] said:
Since you mentioned the F22 problems: I have been wondering why they can't just switch back to LOX bottles. It seems crazy to ground a $300M jet when an oxygen bottle could fix it.
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It's not as simple as it sounds. Think Johnny Cash's "One Piece at a Time" Cadillac.
Now, up to now my plan went all right
'Til we tried to put it all together one night
And that's when we noticed that something was definitely wrong.

The transmission was a '53
And the motor turned out to be a '73
And when we tried to put in the bolts all the holes were gone.

So we drilled it out so that it would fit
And with a little bit of help with an A-daptor kit
We had that engine runnin' just like a song
Now the headlight' was another sight
We had two on the left and one on the right
But when we pulled out the switch all three of 'em come on.

The back end looked kinda funny too
But we put it together and when we got thru
Well, that's when we noticed that we only had one tail-fin
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The guy who runs the FBO where I have my office knows the guy who landed, groggy, the most recent F22. Word is that OBOGGS is many many pounds lighter, and going back to F15 style LOX will require extensive replumbing.....e.g many many hours for the crew chiefs if/when an acceptable mod is designed.

If there's a problem with purity of what's generated (e.g, a toxin) they aren't saying. After ten minutes below 10,000 if it's hypoxia, it should be recovered. It was not.
 
Ron Levy said:
Cabin pressure differential is a factor in combat survivability -- more cabin pressure means more vulnerability. While I don't have the exact specs, it's highly unlikely that the F-22 has the 13.1 psi cabin differential which would be necessary for an 8000 foot cabin altitude (allowing mask-off operation) at 50,000 MSL. To do so would require a ton of extra structure (literally), and weight on a fighter is too critical for that. The big technology change in that department on the F-22 is the use of an On-Board Oxygen Gas Generating System (OBOGGS) instead of LOX bottles to provide the O2 going into the pilot's mask, and it is in that OBOGGS where all the problems are occurring.
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We had MSOGS on the Bone, molecular sieve oxygen generating system. It would mix O2 in increasing levels with increases in cabin altitude. There was a small LOX tank for emergency use only in the case of an MSOGs failure for a rapid descent below 10K MSL.
 
bbchien said:
The guy who runs the FBO where I have my office knows the guy who landed, groggy, the most recent F22. Word is that OBOGGS is many many pounds lighter, and going back to F15 style LOX will require extensive replumbing.....e.g many many hours for the crew chiefs if/when an acceptable mod is designed.

If there's a problem with purity of what's generated (e.g, a toxin) they aren't saying. After ten minutes below 10,000 if it's hypoxia, it should be recovered. It was not.
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There were two pilots on 60 Minutes Sunday "blowing the whistle" on the F-22 saying they would not fly it again until the cause is found. He last pilot to land "groggy" was on also. Very ballsy thing to do if they still want an air force career. Their bosses were not happy.
 
Geico266 said:
There were two pilots on 60 Minutes Sunday "blowing the whistle" on the F-22 saying they would not fly it again until the cause is found. He last pilot to land "groggy" was on also. Very ballsy thing to do if they still want an air force career. Their bosses were not happy.
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Always the dilemma of a whistleblower.

If it kills their careers, there's a hidden lesson about the integrity of all involved.
 
Ron Levy said:
Not quite. That only pressurizes the cabin, but there are limits to max psi differential, and above a certain altitude where cabin altitude gets above 8000 or so, you're mask-on breathing O2 from the O2 system (usually supplied by a LOX bottle) via a diluter/demand pressure/mixture regulator. At 50,000, you are definitely mask-on in any military fighter jet, and the engine compresser bleed tap air is not going into your lungs.
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Ron check: http://www.cobham.com/media/75388/SYSTEM F-16 OBOGS ADV10556.pdf for a detail diagram of the fighter jet oxygen system. Notice that there are no LOX bottles, but a small oxygen tank for the ejection seat for when the pilot ejects at altitude. Oxygen tanks were rule out of military planes due to the fire hazard when exposed to enemy gun fire. The oxygen concentrator is fed at high pressure from the engine compressor stage (bleed air) because of high pressure needed at the concentrator sieve.

José
 
The new F18s had OBOGGS too. They were troublesome in flight test. I don't know if they got it worked out.
 
Ron Levy said:
That system is only in a few planes. Most fighters still have LOX.
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Some of the planes with oxygen concentrators:
AV-8B, TAV-8B, T-45, F-14D, F-22, F-16
F/A-18, F-15E, A-10, A-4AR, AL-X, GR5, T-4,​
T-6A, T-50, F-5, F-2, C-130 and PC-9

José
 
We wear masks from startup to shutdown no matter what. If you are in an ejection seat, you want O2 available without thinking about it. Mask on, OBOGS running. If it fails, you pull wring and the O2 from a bottle in your seat gives you a finite supply. If you need to eject, everything disconnects from the aircraft (you are connected by your mask, G suit, com cord) and you are automatically sucking from that O2 bottle.

The bleed air from the compressor does pressurize the cockpit as well as supply lots of air to the OBOGS system. We switched to OBOGS to save maintenance, cost, complexity, etc...NOT for getting shot at. Think about it, if someone is shooting at me, there are a ton of things that can go wrong that I care about more than an O2 explosion (Which may or may not happen if it can immediately vent to the atmosphere...it is not in the cockpit (talking about LOX, etc). I am sitting on a bunch of fuel, missiles, ammunition, hydraulics (that is highly pressurized hydrocarbons, BTW), carck in the canopy causing rapid decompression (BENDS), etc.
 
Morne said:
I am guessing that the portable oxygen concentrators are not considered sufficient for the required supplemental oxygen to crew, right?
Click to expand...
The Inogen Aviator G2-1265 is good up to 18,000 feet (single person). When my RV-9A is finished I'm getting some kind of O2 system, and the concentrators are attractive, but I doubt I'll fly at altitude enough to come anywhere close to paying for their cost relative to a bottled system.
 
Buggsy2 said:
The Inogen Aviator G2-1265 is good up to 18,000 feet (single person). When my RV-9A is finished I'm getting some kind of O2 system, and the concentrators are attractive, but I doubt I'll fly at altitude enough to come anywhere close to paying for their cost relative to a bottled system.
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Its about convenience of never having to get it filled. Ever.
 
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