Maintaining cruise altitude while depressurised
wannebe,
Because the certification standard is that the cabin NEVER exceeds 40,000, the masks are adequate. The standard implies starting down within one minute and cabin doesn't get above 25,000'. The design is such that only an explosive event would cause an instant 40,000 and that would be a catastrophic unsurvivable event.
GF
Because the certification standard is that the cabin NEVER exceeds 40,000, the masks are adequate. The standard implies starting down within one minute and cabin doesn't get above 25,000'. The design is such that only an explosive event would cause an instant 40,000 and that would be a catastrophic unsurvivable event.
GF
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Funfly you asked
Answer no as long as the crew start a descent fairly quickly. The BAC 111 did not have oxygen masks (except some delivered to the American Airlines.) They could cruise at up to FL350 and in the event of a rapid decompression you had to get down quickly to keep the passengers conscious. While being trained on another aircraft I remember being taught that above about FL380 if there was a rapid decompression and you did not have a mask and the plane did not descend you would be unconscious after about 30 seconds and brain damaged after 2 minutes.
As a passenger, if we are at 40,000ft and loose pressure then I am going to die?
Answer no as long as the crew start a descent fairly quickly. The BAC 111 did not have oxygen masks (except some delivered to the American Airlines.) They could cruise at up to FL350 and in the event of a rapid decompression you had to get down quickly to keep the passengers conscious. While being trained on another aircraft I remember being taught that above about FL380 if there was a rapid decompression and you did not have a mask and the plane did not descend you would be unconscious after about 30 seconds and brain damaged after 2 minutes.
"Mildly" Eccentric Stardriver
Dredging the old memory cells from military times. My understanding is that at about 35,000' 100% oxygen will be equivalent to the partial pressure of oxygen in the air at 10,000'. That is liveable, but you wouldn't want to start doing any vigorous exercise. Above that level, pressure breathing is required, and that is satisfactory up to about 50,000' ( I never flew that high, so stand to be corrected). After that, a pressure suit is required. I think draglift's figures are about correct. In the pressure chamber at 40,000+, the removal of the mask caused almost instantaneous loss of critical faculties.
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Time of Useful Consciousness
Wikipedia has some good info on TUC.
Note that TUC is reduced by up to 50% in the event of a rapid decompression.
https://en.wikipedia.org/wiki/Time_o..._consciousness
Note that TUC is reduced by up to 50% in the event of a rapid decompression.
https://en.wikipedia.org/wiki/Time_o..._consciousness
I cannot imagine why anyone would want to carry out a level 180' turn in the event of decompression at FL410.
Decompression at that level is potentially fatal (in terms of crew l.o.c.) within half a minute or so. The risk of a descent on track is tiny compared to the risk of remaining level and losing consciousness.
Sounds very odd to me.
Decompression at that level is potentially fatal (in terms of crew l.o.c.) within half a minute or so. The risk of a descent on track is tiny compared to the risk of remaining level and losing consciousness.
Sounds very odd to me.
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I can assure you Jack11111 it is true. If it wasn't for the fear of repercussions I would happily give you further details including manual and SUPP references. I assume you don't believe it because it sounds so absurd?
Well, I fully understand that and it's why I put it out there for comment. The obvious thought initially was "is it just Me?" I'm glad you don't believe it. It's the response I was hoping for.
Please realize that this procedure has now been changed but was in play over the last 3 months.
Well, I fully understand that and it's why I put it out there for comment. The obvious thought initially was "is it just Me?" I'm glad you don't believe it. It's the response I was hoping for.
Please realize that this procedure has now been changed but was in play over the last 3 months.
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What sort of "terrain" is around 41,000 feet?
Or am I missing something?
"There is an airline over the last 3 months that has maintained a procedure on certain routes at cruise altitudes up to 41000ft,"
"The requirement was due to terrain but with no work done on escape routes, this was the fix."
Mount Everest is called the world's highest mountain because it has the "highest elevation above sea level". We could also say that it has the "highest altitude". The peak of Mount Everest is 8,850 meters (29,035 feet) above sea level. No other mountain on Earth has a higher altitude
Or am I missing something?
"There is an airline over the last 3 months that has maintained a procedure on certain routes at cruise altitudes up to 41000ft,"
"The requirement was due to terrain but with no work done on escape routes, this was the fix."
Mount Everest is called the world's highest mountain because it has the "highest elevation above sea level". We could also say that it has the "highest altitude". The peak of Mount Everest is 8,850 meters (29,035 feet) above sea level. No other mountain on Earth has a higher altitude
with no work done on escape routes, this was the fix.
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Drift down
Band a lot
It is not quite as simple as being above the terrain. If you have an engine failure or lose pressure at high level you must descend in accordance with a plan. The drift down must end above the terrain so where the terrain is higher than 10.00 you need to put some thought into it ahead of the problem, preferably before flight but in the cruise before reaching the higher terrain will do. Being above the highest terrain in the world sounds great but doesn't solve the problem
It is not quite as simple as being above the terrain. If you have an engine failure or lose pressure at high level you must descend in accordance with a plan. The drift down must end above the terrain so where the terrain is higher than 10.00 you need to put some thought into it ahead of the problem, preferably before flight but in the cruise before reaching the higher terrain will do. Being above the highest terrain in the world sounds great but doesn't solve the problem
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The risk of a descent on track is tiny compared to the risk of remaining level and losing consciousness.
"Mildly" Eccentric Stardriver
And both would carry a similar risk of collision with an aircraft below - but with a "push the yoke forward quick" response, at least the crew of the troubled aircraft would have a chance of seeing and avoiding a potential collision
in the good old days, a turn of 30 degrees off track would solve that problem.
Would it not be better to try to get a clearance before you plummet? Or at least announce what you are about to do and wait a few seconds for ATC to acknowledge? Mild hypoxia amongst a few pax is surely a price worth paying to avoid a you-know-what?
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I have logged two previous notes relevant to this subject:
1. Air Astana flight BKK - ALA travels well west of Almaty before turning 170 (not quite 180) to return to Almaty
If emergency descent over terrain is not a problem then why do they do this?
2. Garuda have still not re-fitted O2 in lavatories on 737-800's.
What is the prospect for someone in toilet getting back to O2 supply before a) passing out 2) dying - especially if modesty lures them into trying to get their pants back on first
1. Air Astana flight BKK - ALA travels well west of Almaty before turning 170 (not quite 180) to return to Almaty
If emergency descent over terrain is not a problem then why do they do this?
2. Garuda have still not re-fitted O2 in lavatories on 737-800's.
What is the prospect for someone in toilet getting back to O2 supply before a) passing out 2) dying - especially if modesty lures them into trying to get their pants back on first
Last edited by WingNut60; 14th Mar 2016 at 01:47.
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Knee-jerk Responses
Whomever/whatever persons/groups decided to take the O2 masks out of the lavs were very myopic; the masks were there for very good reasons. Hopefully this will be universally rectified ASAP, before someone is killed. The cockpit doors being "secured beyond recall" has already resulted in predictable loss of an aircraft; this should also be rectified before another such event occurs. Knee-jerk responses to 9/11 have really hurt aviation; the biggest farce is the existence of the TSA. Sam
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The peak of Mount Everest is 8,850 meters (29,035 feet) above sea level. No other mountain on Earth has a higher altitude
And people go there without supplemental O2 all the time
Many days of slowly ascending allows your body to get acclamated. Plus being in good physical condition.
None of which applies to 99.99 % of a few hundred passengers
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