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Space Forum / Space History / July 2008O2 lack without damage
Why here? Well, this is really a aeromedical query but folks here will have some data, I bet. Quantas had a minor problem with a small hole at altitude. It descended with haste to 10K feet. My questions are about survivablity without O2 while it did. We can assume not everyone paid attention and had a mask on... Yes, you may quickly pass out at say FL330, but: a) How long does it take before there's any real brain damage? This enters into how many things the crew should break to get to 10K faster. Obviously, exceeding Vmax is a bad idea, but by then you have already likely broken off other bits such as the gear doors and maybe the gear. b) Once at 10K, do the O2less folks regain conciousness on their own; and if so, sooner or later?  SignatureA host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 > Why here? Well, this is really a aeromedical query but folks here will > have some data, I bet. [quoted text clipped - 13 lines] > already likely broken off other bits such as the gear doors and maybe > the gear. Never heard of this happening; by the time >those< parts start coming off the aircraft is already disintegrating. > b) Once at 10K, do the O2less folks regain conciousness on their own; > and if so, sooner or later? Seems to me a seated person requires minimum oxygen and probably would remain conscious to at least 20k-25k feet; anyone with impaired breathing of course would be in trouble. Above 25k feet oxygen deprivation leads quickly to impaired cognitive functioning, like one is 'drunk'. It's one thing for the passengers to be impaired, another for the flight crew, eh? The rule of thumb for someone whose heart/breathing have stopped is about three minutes before brain damage begins; above 30k feet with otherwise unimpaired breathing that should be considerably longer. So let's say that descent should be around 10k feet/minute. Many aircraft will operate at over 40k, so a cabin depressurization will be considerably more dangerous. The service ceiling for the Boeing 787 will be 43k feet and Concorde was 60k. Rapid decompression alone would be extremely distressing for everyone at such altitudes, to say nothing of essentially complete oxygen deprivation. Better get that mask on-- quick! So a question arises: for a person breathing pure oxygen, what's the maximum safe altitude to do so for up to 10 minutes? --Damon >> This enters into how many things the crew should break to get to 10K >> faster. Obviously, exceeding Vmax is a bad idea, but by then you have >> already likely broken off other bits such as the gear doors and maybe >> the gear. >Never heard of this happening; by the time >those< parts start coming >off the aircraft is already disintegrating. There are, I believe, both "max extend" and a higher max "have gear out" speeds. ISTM SOP is to throttle back, pull up to kill speed; then drop gear and raise speedbrakes, THEN nose-over to max safe decent speed. Obviously, if you are willing to sacrfice the gear doors and/or gear, you can exceed those. During the TWA 841 dive, for example, the captain dumped the gear at ~~390-470 knots; I doubt THAT is within Boeing's limits... SignatureA host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 David Lesher <wb8foz@panix.com> wrote in news:g6o7qh$jun$1 @reader1.panix.com: >>> This enters into how many things the crew should break to get to 10K >>> faster. Obviously, exceeding Vmax is a bad idea, but by then you have [quoted text clipped - 12 lines] > dumped the gear at ~~390-470 knots; I doubt THAT is within Boeing's > limits... Scary. Imagine the scenario of a Concorde at 60,000 feet and Mach 1.whateveritdid. Has to kill three times the speed and drop 40,000 feet or more after passengers/crew are exposed to a near-vacuum. I doubt putting the engines into reverse at altitude and cruise speeds would be a survivable option, too. --Damon > Many aircraft will operate at over 40k, so a cabin depressurization will > be considerably more dangerous. The service ceiling for the Boeing 787 [quoted text clipped - 3 lines] > quick! > At 60,000 feet you are probably going to get the bends if you aren't wearing a pressure suit, as the nitrogen in your blood becomes gaseous. There's also other goodies like burst eardrums to consider. Although it wouldn't have done any good for passenger confidence, it might have been smart to have had the pilot and copilot of the Concorde wear pressure suits. Certainly if it had been a military aircraft operating at that altitude they would have been wearing pressure suits. There's stuff on depressurization here: http://www.sff.net/people/geoffrey.landis/vacuum.html > So a question arises: for a person breathing pure oxygen, what's the > maximum safe altitude to do so for up to 10 minutes? This emergency passenger mask was certified for continuous use at 40,000 feet: http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA305614 What makes the Qantas accident interesting is that the cause of the accident - the rupturing emergency oxygen tank - both damages the aircraft while at the same time taking away the crew's ability to deal with the emergency by not giving them oxygen. In short, a emergency safety system that can cause a fatal accident, rather than prevent one. Apparently, the tank mountings were suspect before the accident: http://www.timesonline.co.uk/tol/news/world/article4414114.ece Pat Qantas blast damaged landing systems, according to this newspaper: http://www.news.com.au/dailytelegraph/story/0,22049,24101664-5001028,00.html The ATSB bugle is careful not to say that himself, however. >What makes the Qantas accident interesting is that the cause of the >accident - the rupturing emergency oxygen tank - both damages the [quoted text clipped - 3 lines] >In short, a emergency safety system that can cause a fatal accident, >rather than prevent one. True, and a situation we often face. Take the Apollo fire. The hatch design was influenced by Gus's Mercury flight.. >Apparently, the tank mountings were suspect before the accident: >http://www.timesonline.co.uk/tol/news/world/article4414114.ece I believe Qantas has stated the warning did not apply to the aircraft involved. SignatureA host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433 |
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