Maintaining cruise altitude while depressurised
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Maintaining cruise altitude while depressurised
There is an airline over the last 3 months that has maintained a procedure on certain routes at cruise altitudes up to 41000ft, that if a depressurisation occurs, cruise altitude must be maintained until the completion of a 180 degree turn (over 4 mins at 480 knots).
This has recently been discontinued but I am interested in any comments and whether any other airlines around the world would or have entertained such a procedure.
This has recently been discontinued but I am interested in any comments and whether any other airlines around the world would or have entertained such a procedure.
Legal (certification) requirement is to commence an emergency descend within one minute.
Any more time would require an approval, for that an analysis of the available oxygen would be required.
Another constraint are the passenger oxygen masks. Most are effective only below 25000 ft so the time to get there is limited.
Any more time would require an approval, for that an analysis of the available oxygen would be required.
Another constraint are the passenger oxygen masks. Most are effective only below 25000 ft so the time to get there is limited.
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This has recently been discontinued but I am interested in any comments and whether any other airlines around the world would or have entertained such a procedure.
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I don't recall the exact altitude, but from what I remember from altitude chamber classes while in the Air Force, one has to "pressure breath" 100% O2 when the ambient pressure drops below a certain level.
Only the cockpit masks are designed to do this.
The passenger masks are not designed, nor are able, to force oxygen under pressure through the lungs and into the hemoglobin above a certain pressure level.
I seem to remember that the critical level below which the passenger masks start to become effective is somewhere around 30,000 ft. (could be mistaken)
Only the cockpit masks are designed to do this.
The passenger masks are not designed, nor are able, to force oxygen under pressure through the lungs and into the hemoglobin above a certain pressure level.
I seem to remember that the critical level below which the passenger masks start to become effective is somewhere around 30,000 ft. (could be mistaken)
Last edited by wanabee777; 12th Mar 2016 at 08:32.
Cockpit oxygen masks are not pressure masks. They are capable of a slight positive flow for the purpose of keeping smoke out of the mask and goggles but they do not provide pressurized o2 to the lungs.
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30,000 ft sounds about right.
Obviously, you would want to descend well below that level for the flight attendants and passengers to get adequate amounts of O2 into their blood stream.
Obviously, you would want to descend well below that level for the flight attendants and passengers to get adequate amounts of O2 into their blood stream.
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Cockpit oxygen masks are not pressure masks. They are capable of a slight positive flow for the purpose of keeping smoke out of the mask and goggles but they do not provide pressurized o2 to the lungs.
Likewise wanabee
Certainly the placard on the regulator our 777 flightcrew Eros masks states that pressure breathing is available up to 35?-?40K . Not at work at the moment so can't check the exact figure.
Certainly the placard on the regulator our 777 flightcrew Eros masks states that pressure breathing is available up to 35?-?40K . Not at work at the moment so can't check the exact figure.
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The airbus Eros masks are not pressure masks.....but they mix ambient and oxygen below approx 33,000 feet - providing 100% oxygen above this level. I think this is what the previoys respondents are thinking about.
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Pressure breathing equipment requires a different training regime. You do not, and will not, have pressure breathing equipment on an aeroplane for which you are not trained in its use. You have a mask that has an overpressure for the smoke scenarios and it provides 100% oxygen above approx 30000 feet. It mixes this with ambient below this level.
These masks increase the amount of O2 available to you and do NOT work by increasing the pressure of the O2 to get it into your haemoglobin. It is the partial pressure of the O2 within the gas (atmosphere) that does this. The O2 partial pressure decreases as we climb, which is why more O2 is required. We are NOT pressure breathing in a decompression.
These masks increase the amount of O2 available to you and do NOT work by increasing the pressure of the O2 to get it into your haemoglobin. It is the partial pressure of the O2 within the gas (atmosphere) that does this. The O2 partial pressure decreases as we climb, which is why more O2 is required. We are NOT pressure breathing in a decompression.
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Very much doubt that. You will need to have done a course on pressure breathing if it were fitted. It isnt the sort of thing that you learn 'on the job' when you have just depressurised.
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Proper pressure breathing kit requires you to forcibly breath out against a lot more positive pressure than is provided by airline O2 masks. The stuff on airliners, whilst it might be called pressures breathing, most definitely isn't.
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The only courses I ever had involving pressure breathing O2 were over 40 years ago when we were required to go to the altitude chamber every 2 or 3 years while I was in the military. No training, in that regard, with my airline.
I don't recall the act of "pressure breathing" O2 to be all that complicated or involved.
I don't recall the act of "pressure breathing" O2 to be all that complicated or involved.