Oxygen use at high altitude

[JammedStab]

Any high flyers up around 490-510 using oxygen for the flight. Curious what your cabin altitude is.

[deefer dog]

Made 490 once...only just, and only to tick the box. Won't be doing it again in a hurry. Scary up there and in most things if you should be there you should be at TOD.

Both on O2 btw.

[noneya]

In the G650 - Cabin Altitude at FL510 is 4,850
- Cabin Altitude at FL410 is 3,300

[JammedStab]

Made 490 once...only just, and only to tick the box. Won't be doing it again in a hurry. Scary up there and in most things if you should be there you should be at TOD.

Both on O2 btw.

Thanks,

I have never been up that high. I assume that you use the normal O2 selection. Is much O2 actually used for a significant length of period on oxygen or is the mixture so low that hardly any is used.

[JammedStab]

No one answered the question. Just read an article about the question....

High-altitude Oxygen Rule: Compliance Conundrum | Business Aviation News: Aviation International News (http://www.ainonline.com/aviation-news/business-aviation/2015-06-26/high-altitude-oxygen-rule-compliance-conundrum)

High-altitude Oxygen Rule: Compliance Conundrum

Most professional pilots are diligent about following the rules except, of course, on those relatively rare occasions when they don’t agree with them. One of the standouts among ignored rules is 91.211, which governs the use of supplemental oxygen, said Rick Miller, chief pilot for Merck Sharp & Dohme, at the recent Business Aviation Safety Summit. The rule requires that above 41,000 feet, one pilot must use the mask at all times even with another pilot in the cockpit. The pragmatic reason behind 91.211 is to ensure pilots can maintain control of the aircraft in the event of a high-altitude explosive decompression. At 50,000 feet, the time of useful consciousness is a mere six to nine seconds, about the time that passes between pulling the power to idle over the threshold and touching down on the runway.

“This regulation as it applies to the use of supplemental oxygen above 41,000 feet is probably one of the clearest in Part 91,” he said. However, he maintained, non-compliance seems to be the norm, and incidents of non-compliance are not the result of pilots who don’t understand the rules, Miller noted. He cited an NTSB study of 500 Part 91 pilots that asked whether they use their masks above 41,000. Only 18 percent said yes. “It’s important as a chief pilot to maintain a high level of safety and professionalism in my organization and a good safety culture,” he added. “This regulation is one of the biggest challenges I’ve had over the years. But how do you operate a disciplined cockpit environment when people cherry pick the regulations they’ll follow? There must be a better way.”

If so many pilots ignore the rule, should the industry force it on violators, or should the rule be tweaked to align with Europe’s regulations, which recommend the use of oxygen above 41,000 feet? “The FAA and NTSB don’t seem concerned about addressing this situation,” Miller said. “I’m frustrated that I’m one of the few [chief pilots] out there forcing my pilots to comply. I don’t know why the FAA and NTSB don’t look at this more closely.” Miller is currently working with Gulfstream and others to better understand why there is so much disregard for the regulation, as well as potential solutions. One insight that emerged early in the session was that the quick-donning masks are normally considered emergency equipment. What company operates an aircraft regularly using a piece of emergency equipment?

Miller said the arguments for or against a change to the regulation must focus on determining the severity of the threat facing flight crews when they avoid wearing the masks at high altitude. “What’s our tolerance for this kind of situation when a rapid decompression could translate into the loss of lives?” Miller wondered, especially in light of the certification standards on many new high-altitude-capable aircraft? “[Manufacturers] had to prove a rapid decompression is a one in a billion chance. This is such a highly unlikely event it is really considered an acceptable risk.”

Changing the FAA’s mind about anything is no small challenge. Miller said some recent SMS risk assessments he conducted uncovered a list of problems created by wearing oxygen masks for extended periods at high altitude that he believes might support a change. A series of instant polls conducted at the summit by Francois Lassale of Vortex FSM added fuel to the fire for a pragmatic change to the 91.211 problems (see box).

[CL300]

having flown a lot above FL450, we had a device ( actually two) which were concentrating the O2 from the cabin, and through an humidificator to nose canula.
These little tubes were not interfering with normal ops, not picking into the O2 reserves of the plane, had no chemical in it. However when a pilot was leaving his seat, the other one was putting on the real thing.
even this a relatively low cabin altitude, this extra O2 was really nice on 12+ hours trip.
Cannot get my hands on the documentation of it but was surely STCd, since it was hard installed in the plane. GLEX by the way.

[BizJetJock]

But that's missing the point of the rule. In the event of a rapid decompression would you realistically be able to overcome the startle factor and get your emergency mask on within the time of useful consciousness? Probably not.
And that's before the question of whether you will actually be able to breath if the mask has gone into pressure breathing mode. If you have never practiced it then the chances are very low.
So in an aircraft without automatic emergency descent, in the event of a rapid depressurisation above 40k your chances of survival are slim.:sad::sad:
However, as has been pointed out, the manufacturers have had to show that the chance of a rapid decompression (that isn't catastrophic for other reasons) is extremely low, so you would think that in aircraft with automatic ED mode then the requirement is unnecessary.

[CL300]

Well, **** must happens sometimes. we had an LOA that was stating that this oxygen supplement was covering the use of supplemental oxygen requirement in the FAR, and leaving the 02 bootle intact for emergency use ( notwithstanding the confort of wearing the mask for 12 hours).
we have been ramp checked many times with this system, the FAA folks were actually looking at the pressure gauge of the bottle, but LOA rules and never had an issue with this system.

as far as decompression is concerned, this a whole different story i believe..

[Joe le Taxi]

I would say most professional pilots should be able to don a quick don mask in 9-15 seconds (provided its not submerged under magazines, sandwiches etc). The key is to permanently be primed to put it on at the first sign of trouble.

I would sometimes take it out and put it on my lap at the higher levels, so that I could be confident of donning it within a couple of seconds. It really isnt practical to wear one continuously on a long haul sector, but range would be very restricted on a global or gulfstream if it couldn't go higher than 410.

And that's before the question of whether you will actually be able to breath if the mask has gone into pressure breathing mode. If you have never practiced it then the chances are very low.

It feels odd at first, but again; not at all difficult, even on the first try.

[HyFlyer]

In the G650 - Cabin Altitude at FL510 is 4,850
- Cabin Altitude at FL410 is 3,300


May come as a shock for the big jet jockeys,

but the lill'ol SJ30 has a sea-level cabin at FL410
It also has a ceiling of FL490..... Delta PSI of 12 is kinda stunning.

Food for thought.

[GlenQuagmire]

I've heard stories of ramp inspectors looking at oxygen levels after a flight to determine whether or not a mask was used but when the mask is in diluted demand (normal) it's not delivering any oxygen at all at normal cabin altitudes is it? Or if it is it's a trace amount. So what can they infer by looking at the gauge?

[PURPLE PITOT]

GQ, you can infer that they don't know what they are talking about. Hence they don't have a proper flying job.

[JammedStab]

That is what I would like to double check, in Normal is any O2 used(for various A/C types) at normal cabin altitude.


According to this article....

http://aviationweek.com/bca/it-s-not-about-breathing

"It is more instructive to discuss what the regulator does for the pilot in the “normal” position. How much oxygen are we receiving sitting on the ground? How about at altitudes like 10,000 ft., 18,000 ft., 30,000 ft. and 43,000 ft.?

Let’s assume the oxygen regulator has been designed to produce oxygen at a partial pressure of 3.0 psi to the lungs of the pilot. At sea level that’s the pressure that already exists, so the regulator, in “normal,” delivers ambient air to the pilot at a cabin altitude of sea level. This is why I used to smile when I heard certain European inspectors would check the oxygen remaining to insure crews had oxygen masks on when above FL 370. At the cabin altitude that a properly functioning pressurization system would provide at FL 370, the regulator would be delivering almost completely ambient cabin altitude to the pilot and the amount of oxygen used wouldn’t decrease noticeably over several hours."

[GlenQuagmire]

Not read that before but I'm pleased that they work the way I thought they did. I've never worn one for a long period because they hurt my delicate face but I wouldn't expect to see any consumption at all at normal cabin altitudes.

I've never understood why the cabin pressure warning is set so high. Why not warn the crew at an earlier stage of an abnormal cabin pressure? I'd quite like a gentle nudge at 7000' cabin alt rather than 3000 feet later.. Can't be that difficult to sort an algorithm that accommodates high elevation airports but flags up a problem when the cabin starts climbing off schedule.

The lack of replies probably gives an indication of the number of crew that wear one in the cruise..

[Jwscud]

On many aircraft you do get extra warning. The Lear 40/45 gives you:

- Amber CABIN ALTITUDE at 8750'
- EMER PRESS kicks in at 9500'
- Red CABIN ALTITUDE plus the voice finally at 10,000'

Obviously if it's catastrophic, all those will go at once, but hopefully the amber warning will give you a chance to get the mask on before starting the dive of doom.

[Stewpadasso]

Normal flight below 370, no. I don't wear it. Above 370 it is out of the carrier. I don't believe any contortionist can reach a mask in 5 seconds, time your self in the plane at cruise. Out of the blue scream at your copilot " get your mask NOW!" (Don't forget to video it so we can all laugh later)

Installed (certified part 25 plane) bottle is only big enough for emergency descent/smoke. No using it for a 3 hour flight above 350.

In Normal mode the mask will still use O2.

Been to 510. Masks on. 100% pressure breathing. Had an empty plane. Empty, cold, and out of gas is the only way it will get there. Not really practical. The overspeed/stall tapes were close. Got a picture somewhere...

470-490 was not uncommon, but the boss did NOT like being up there. He read enough to realize how inhospitable that environment is.

Mask switched to normal won't help you up there. Yes the mask is supposed to automatically switch, but if you are going to have a bad day, it will probably fail to.

Above 410 one mask was out and ready. Above 450 one mask (Eros) was around the neck. The SMALL bottle the manufacturer installed to meet the certification/survival requirement does not have enough air to cruise with mask delivering for the duration above 410, let alone 350. You have to have the minimum for smoke/fire to get the plane on the ground.

A better question is " in the sim, when you do rapid decompression/emergency decent, when do you take off the mask." The correct answer is "when the aircraft is stopped on the runway so I can get out." But no one does that in training, so we will fly like we train.

Explosive decompression isn't the issue. A gradual increase of cabin altitude leads to the euphoric hypoxia that prevents the ability to place the mask on and use it. A Lear 31with the bleeds off will make it to 230 before the cabin warning goes off. (Or so a bird told me). Mask goes on pretty fast. But The cabin was at 15500 before we got a horn. Not really where it was supposed to go off.

Remember these rules were made a LONG time ago. Believe it or not, airplanes were flying a while before anyone decided to stick a computer inside to make a pilots life easier.

At 470-510 an explosive decompression is going to freeze your eyeballs and another point to consider is that lovely mask you are counting on is probably only certified for use below 410 (the newer ones are 450). The reason themanufacturer gets away with that slight of hand is showing that the aircraft can get below 410 BEFORE the cabin gets to 410.

Put the mask on in flight, do it enough to realize that glasses are in the way, the headset really slows down getting it on. Breathe with it. Do dearth Vader. Figure out how to get the mask held to your face and drag the straps over your head. Then hope you never need that knowledge, kinda like V1 cuts...

[GlenQuagmire]

I went to 510 during an air test recently and the aircraft got there with ease with over 10,000lbs of fuel leaving 470. Initially we arrived at at 510 with a speed of 0.77 and slowly accelerated to 0.8. The high speed and low speed tapes are at 198 and 158 at that altitude and 0.77 was approximately 180 indicated. Oxygen was at 97% at the start of the flight and either I or the co pilot or both had the mask on in normal for around 2 hours and the oxygen was 96%when we parked. I attribute this difference to the bottle getting cold rather than the oxygen actually being consumed. I am doing a fairly long flight in a few days and I will sit there doing the darth as high as practical (probably 490) for as long as I can stand it and report back. My gut feeling is that it won't consume any oxygen and will make drinking tea very difficult.