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Oxygen masks after EMER Descend

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Oxygen masks after EMER Descend

Old 14th Jul 2023, 05:22
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Oxygen masks after EMER Descend

Good morning,

quick one: at which cabin alt it is safe to take off the crew oxygen mask? I heard a lot of opinions there, like mountains have 8000ft so its safe. Any hints on that?

Thanks SW
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Old 14th Jul 2023, 09:33
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In EASA land, this issue is regulated by article CAT.OP.MPA.285 of AIR-OPS.
CAT.OP.MPA.285 Use of supplemental oxygen The commander shall ensure that flight crew members engaged in performing duties essential to the safe operation of an aircraft in flight use supplemental oxygen continuously whenever the cabin altitude exceeds 10 000 ft for a period of more than 30 minutes and whenever the cabin altitude exceeds 13 000 ft.
Of course, airline SOP can define more stringent requirements.
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Old 14th Jul 2023, 10:57
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US regulations differ between Parts 91, 135 & 121. The latter being more stringent.

Oxygen masks typically deploy automatically at around 14,500’ on a Boeing, warnings go off at 10,000’. Take your pick.

It will vary between individual: age, weight, fitness, alcohol etc. As Luc says - it may depend on your company Ops manual.
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Old 14th Jul 2023, 15:33
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There is the theory and the real life experience. Back when I was flying in Africa, we used to cruise in non pressurised aircraft for a couple or hours at FL120 and sometimes at FL130 with very old passengers. Apart from the frequent farting and pax falling asleep, I never had or heard any issues… So definitely no concern at all from FL130 and below for an healthy person at least.
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Old 14th Jul 2023, 16:08
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Most healthy pilots will have no problem flying at FL120 or FL130, and some of them will have slightly impaired cognitive abilities.
And for the very same pilot, the situation could vary depending on how long ago he had his previous meal and where is the current time in his circadian cycle.
Therefore, the regulation allows for some margin.

The NCO regulation that applies to my flying is a bit more flexible; it requires the pilot in command to assess whether the level of oxygen at the flown altitude can impair the abilities of the pilot and to take measures against it.
I routinely use a finger pulse oximeter when I fly above 10,000 ft.
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Old 14th Jul 2023, 22:37
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Salute!

Thank you, Luc

My pulse oximeter is super, and according to the literature, FAA likes 92% saturation in daylight and higher at night.

Not hard to keep one charged in the cockpit, and after an emergency descent you can see how well you are doing.

And by the way, in a high workload even as low as 7,000 or 8,000 feet you can get in trouble, especially if you are not in good shape.

Gums sends...
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Old 17th Jul 2023, 00:40
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even as low as 7,000 or 8,000 feet you can get in trouble
At night the USN required oxygen above 5,000, 10,000 day, if my aging memory recalls correctly.
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Old 17th Jul 2023, 02:14
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Salute!

Thanks, Megan.

Very hard for me to find the FAA recommended oxy saturation numbers, but I recall 92%....regardless of altitude.Below 92% , FAA claims that cognitive ability and physical reaction times are impaired.

The altitude rules are averages of folks' physiology and averages of atmosphere pressures and such we might encounter. I would prefer actual oxygen saturation as I see when monitoring, and ditto for cabin contamination versus a simple altitude measurement.

Gums sends...
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Old 17th Jul 2023, 08:13
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Originally Posted by gums
in a high workload even as low as 7,000 or 8,000 feet you can get in trouble, especially if you are not in good shape.
Normal cabin altitude in a pressurised aircraft is 8,000ft so pilots and passengers are exposed to that all the time.
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Old 17th Jul 2023, 15:27
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Salute!

Well aware of that, PJ.

I use that altitude because it is my cabin altitude, and until I succumbed to lung damage built things, moved things, cut down/sectioned trees for firewood and easily ran up and down the river there to fish and, and.... That being said, we routinely have a few sea level folks experience no kidding "altitude sickness" verified by real doctors at nearby Woodland Park, which is about the same altitude - 8,000 ft advertised, but as low as 7,800. So old and infirm folks are advised to spend a quiet day or two there before heading up to Breckenridge, which is 9,000 ft and higher.

My point is a personal monitoring device is better than simple cabin pressure device. The histoxic problems are more complex, as it takes time to rid your blood of some chemicals or gases you absorbed. Think about how long we pre-breath to get rid of nitrogen for our chamber rides.

On the plus side, my concentrator dramatically increases my saturation without the slight positive pressure that some systems employ, especially the folks in the U-2 or WB-57. Many of us that flew some of the old interceptors breathed under slight pressure all the time to avoid the bends from rapid de-compress, and it was not all that bad after a mission or two to get used to it.

So point is simply descending below 10,000 feet may not be enough to treat hypoxic events.

Gums sends...


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Old 17th Jul 2023, 19:04
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When I was a lot younger, I would routinely fly gliders to 10,000’ with short periods up to 12,500’, with no hypoxia symptoms. Note that I lived then and now at 3500’ ASL.

Two years ago, aged 73 but still with a Category 1 medical, I spent 10 days flying at a gliding camp at Valemount BC (2600’ ASL). At the end of the camp, I ferried a tow plane through the Rockies, back to its base near Calgary. It was a spectacular CAVOK day with booming thermals, which made for a rough trip, but I thoroughly enjoyed it and took lots of spectacular photos.

The first two hours of the flight were between 9,000’ and 10,00’, as I followed the Jasper-Banff Highway (the Icefields Parkway). At Lake Louise, I took the direct route home “over the rocks” and flew the last hour at 10,000’ to 11,000’.

After I had landed and shut down, I was lethargic and slightly disoriented. Although I could recall many details of the flight, including a perfectly satisfactory landing, I couldn’t remember if I had put the flaps down!

I realized I was hypoxic. Now when I fly gliders on thermalling flights (8,000’ to 12,000’), I use oxygen which not only avoids hypoxia, but has the added benefit of reducing tiredness at the end of a long flight.

The Mountain High electronic regular that I use, feeds puffs of oxygen during inhalation, through a nasal cannula. It is so convenient and easy to use that I use it for the whole flight. Hopefully no more hypoxia for me.
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Old 18th Jul 2023, 16:00
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Originally Posted by megan
At night the USN required oxygen above 5,000, 10,000 day, if my aging memory recalls correctly.
Not sure your recall is up to scratch this morning.
The requirement for unpressurized aircraft in the NATOPS is 10,000' and above. Our usual ceiling / limit even with oxygen for unpressurized cockpits was 25,000 feet.
*scratches head*
Not sure where you got the 5,000 from, but if you flew jets with the USN back in the very old days there may have been a rule (type specific to the A-4 perhaps?) about that in one of the manuals.
If I can find an old T-45 NATOPS (I used to have one in e-form some years ago) I'll see if I can find a ref to "get your O2 mask on by 5,000 because ..." I don't recall that being in the brief on the few occasions I got to fly in one.
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Old 18th Jul 2023, 17:18
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Salute!

Yeah, Wolf, could have new NATOPs or USAF numbers, but I flew with the 10,000/25,000 ft rule for about 4 years and we routinely came home from a long way or cruised on a x-country at 25,000 k..... our regulator garadually increased O2 percentage and then we got positive pressure above 20,000 or so, but very slight.

reason to get on the nose hoze early is for future problems....

I still like person sensors more than cockpit sensors to help you.

Gums sends...
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Old 19th Jul 2023, 01:15
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Not sure your recall is up to scratch this morning
Well, I did tell you Lone I'd fancy a bet though on the 5,000, that was mid '60's flying the T-28 during training at Whiting, Saufley and Mainside. Perhaps type specific with the exhaust stacks by your feet, cockpit carbon monoxide tests were a regular in flight maintenance check carried out by instructors that had to be signed off, students used to have to do frequent canopy checks during flight to ensure it was closed as well, being hydraulically operated it could creep open.

Found the flight manual, would seem procedure fell under the Unit doctrine as spelled out in "Normal Operation".



Last edited by megan; 20th Jul 2023 at 06:19. Reason: Scan
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Old 23rd Jul 2023, 15:25
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Originally Posted by gums
Salute!

Thank you, Luc

My pulse oximeter is super, and according to the literature, FAA likes 92% saturation in daylight and higher at night.

Not hard to keep one charged in the cockpit, and after an emergency descent you can see how well you are doing.

And by the way, in a high workload even as low as 7,000 or 8,000 feet you can get in trouble, especially if you are not in good shape.

Gums sends...
That was a good joke, checking your oxygen levels with an oximeter after an emergency descent, very convenient given the situation and the LAND ASAP on the ECAM.
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Old 23rd Jul 2023, 20:24
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Concur with Pineteam. You won't get far in Africa treating Fl100 as the oxygen threshold - you'd spend a fortune on the stuff if you could even get hold of it.
I used to consider it (for self and pax) if above Fl120 if staying there for a considerable time and always used it above that level.
I was advised to be aware of Nilotic (true black) Africans (ie not Semitic/Arabic - as in Ethiopians/Somalis) who apparently suffer widely from genetic sickle-cell anaemia which has a great effect on oxygen uptake and did encounter one such chap who got terribly distressed at Fl90 and swore he was dying - we descended into the turbulence to Fl50 and he perked right up - though I didn't! Strongly suspected he was anaemic.

It's a very unpredictable and variable business.
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