DL 767-300 decompression (DL 2353 9/18)
Sep 20, 2019, 1:24 pm
#46
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Climbing a peak is not the same as sudden decompression. Your body has time to acclimatize when you are climbing a mountain. When the cabin of an aircraft loses pressurization, your body effectively is going from 6-8k feet to whatever the external altitude is within 1-2 seconds.
Again, those people are acclimatized, not experiencing a rapid decompression. The human body can acclimatize up to ~8,000m, but it takes months to achieve this. A sudden decompression to 14k feet gives around 30 mins of useful consciousness.
There's an exemption for quick deploying masks. Really, the most sinister type of decompression is when there is a bleed valve issue or something similar, where the pilots slowly lose situational awareness due to hypoxia. This is what killed Payne Stewart and what happened with the Helios flight in 2005. The pilots will set an altitude in the autopilot and slowly become hypoxic, which makes it even harder for them to identify that there is an issue.
Again, those people are acclimatized, not experiencing a rapid decompression. The human body can acclimatize up to ~8,000m, but it takes months to achieve this. A sudden decompression to 14k feet gives around 30 mins of useful consciousness.
There's an exemption for quick deploying masks. Really, the most sinister type of decompression is when there is a bleed valve issue or something similar, where the pilots slowly lose situational awareness due to hypoxia. This is what killed Payne Stewart and what happened with the Helios flight in 2005. The pilots will set an altitude in the autopilot and slowly become hypoxic, which makes it even harder for them to identify that there is an issue.
Sep 20, 2019, 4:11 pm
#47
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MSP media are reporting that this happened again. On Monday, a 757 flight to MSP from SLC diverted to Rapid City. Oxygen masks weren't deployed. Apparently at least one TV station was contacted by a local couple on the flight.
Sep 20, 2019, 4:33 pm
#48
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IIRC, Leadville, CO is the highest incorporated town in the US at 10,152'. It has about 2800 people.
But looking outside of the US it's easy to find large populations at altitude.
La Rinconada, Peru: 16,732 with ~50,000 people
Nagqu, Tibet: 14,800 with ~42,000 people
Juliaca, Peru: 12,546 with ~216,000 people
Cusco, Peru:11,152 with ~428,000 people
El Alto, Bolivia: 13,620 with ~846,000 people
Quite a few more of varying sizes: https://en.wikipedia.org/wiki/List_of_highest_cities
But looking outside of the US it's easy to find large populations at altitude.
La Rinconada, Peru: 16,732 with ~50,000 people
Nagqu, Tibet: 14,800 with ~42,000 people
Juliaca, Peru: 12,546 with ~216,000 people
Cusco, Peru:11,152 with ~428,000 people
El Alto, Bolivia: 13,620 with ~846,000 people
Quite a few more of varying sizes: https://en.wikipedia.org/wiki/List_of_highest_cities
Cant seem to find anything online about this. Seems weird to lose pressure but not have masks deploy. Curious if issue was something else.
Sep 20, 2019, 4:38 pm
#49
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These are used to higher altitude. Also despite these not being small numbers of people, even in total they're not even .01% of the Earth's population.
Cant seem to find anything online about this. Seems weird to lose pressure but not have masks deploy. Curious if issue was something else.
Cant seem to find anything online about this. Seems weird to lose pressure but not have masks deploy. Curious if issue was something else.
Sep 20, 2019, 7:23 pm
#50
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Yes, but you don't go from 8k to 14k in a couple of seconds. Also people who climb up peaks like that are likely a bit fitter then your average passenger. Thirdly there is an FAR on O2. Simply stated -As a pilot you have to use supplemental oxygen if you fly more than 30 minutes at cabin pressure altitudes of 12,500 feet or higher. And that at cabin altitudes above 14,000 feet pilots must use oxygen at all times. And that above 15,000 feet each occupant of the aircraft must be provided supplemental oxygen. All of this is spelled out in Federal Aviation Regulations Part 91.211.
Sep 20, 2019, 9:07 pm
#52
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IIRC, Leadville, CO is the highest incorporated town in the US at 10,152'. It has about 2800 people.
But looking outside of the US it's easy to find large populations at altitude.
La Rinconada, Peru: 16,732 with ~50,000 people
Nagqu, Tibet: 14,800 with ~42,000 people
Juliaca, Peru: 12,546 with ~216,000 people
Cusco, Peru:11,152 with ~428,000 people
El Alto, Bolivia: 13,620 with ~846,000 people
Quite a few more of varying sizes: https://en.wikipedia.org/wiki/List_of_highest_cities
But looking outside of the US it's easy to find large populations at altitude.
La Rinconada, Peru: 16,732 with ~50,000 people
Nagqu, Tibet: 14,800 with ~42,000 people
Juliaca, Peru: 12,546 with ~216,000 people
Cusco, Peru:11,152 with ~428,000 people
El Alto, Bolivia: 13,620 with ~846,000 people
Quite a few more of varying sizes: https://en.wikipedia.org/wiki/List_of_highest_cities
Clearly my question was about sizeable towns above 12,000' in COLORADO.
So far we have . . . zero.
Sep 20, 2019, 9:15 pm
#53
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These are used to higher altitude. Also despite these not being small numbers of people, even in total they're not even .01% of the Earth's population.
Cant seem to find anything online about this. Seems weird to lose pressure but not have masks deploy. Curious if issue was something else.
Cant seem to find anything online about this. Seems weird to lose pressure but not have masks deploy. Curious if issue was something else.
Passengers on the diverted DL 1695 apparently were boarded onto another DL plane to continue the trip to MSP.
ADDED: According to flightaware, they did indeed fly somewhat slowly at approximately 10,000 ft for a long while and then diverted to Rapid City, continuing to MSP the next morning in an A320. [I've been on flights that have done something like this (flying somewhat slowly and definitely at very low altitude for a mainline jet, but without rapid descent) in response to a mechanical issue, but there wasn't a decompression. In my case, we landed at the intended airport and were met by fire equipment, although nothing happened and we were soon permitted to deplane through the jetway.] It's a bit curious that the pilots decided to go to Rapid City rather than some larger airport in Colorado, such as DEN, but perhaps the mechanical problem became worse as the flight continued even at low altitude. I'd guess that a 757 would be an unusual sight at Rapid City. I wouldn't expect DL to have staff and hotels available there at midnight, so it's surprising that reports have said nothing about the overnight arrangements.
Somewhere there should be a record of a rescue A320 flight to Rapid City and a special section or ferry flight to get the DL 757 out of there.
Last edited by MSPeconomist; Sep 20, 2019 at 9:29 pm
Sep 20, 2019, 10:30 pm
#54
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It was DL 1695 on Monday (September 16...
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It's a bit curious that the pilots decided to go to Rapid City rather than some larger airport in Colorado, such as DEN, but perhaps the mechanical problem became worse as the flight continued even at low altitude. I'd guess that a 757 would be an unusual sight at Rapid City. I wouldn't expect DL to have staff and hotels available there at midnight, so it's surprising that reports have said nothing about the overnight arrangements.
...
It's a bit curious that the pilots decided to go to Rapid City rather than some larger airport in Colorado, such as DEN, but perhaps the mechanical problem became worse as the flight continued even at low altitude. I'd guess that a 757 would be an unusual sight at Rapid City. I wouldn't expect DL to have staff and hotels available there at midnight, so it's surprising that reports have said nothing about the overnight arrangements.
Sep 20, 2019, 10:43 pm
#55
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again, I’m pretty sure that once the pilots declare an emergency, the flight manual and ops manual procedures — in no uncertain terms—say “Land at the nearest suitable airport”
Sep 20, 2019, 10:51 pm
#56
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The N1608, one of the newest 763s in the fleet that often got used for transpacific flights (e.g., SEA-PEK and SEA-ICN), also had a loss of cabin pressure a couple of years ago: Incident: Delta B763 near London on Aug 13th 2017, loss of cabin pressure.
Sep 21, 2019, 6:02 am
#57
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1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;
I understand the cabin altitude on this flight only got to about 15,000 feet.
Sep 21, 2019, 6:11 am
#58
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There's a JustPlanes cockpit ridealong in a Challenge 757 which came out in the late 1990s in which the first segment is MIA-LPB. Prior to arrival (and again just after takeoff to UIO), the pilots don oxygen masks and set the cabin pressure altitude to 13,000 feet. I knew the reasons to go on oxygen given that scenario, but never fully understood why they were setting the cabin altitude to that point (assuming some sort of procedure to adjust to the high altitude?) .
Sep 21, 2019, 6:40 am
#59
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I think the argument has morphed into: Can people actually be "usefully conscious" at altitudes above 12,000 feet? Clearly, they can.
My BF and I drove up Trail Ridge Road in RMNP. He's acclimated to Boston; I'm acclimated to Denver. At the top, he bounded out of the car and wanted to climb the hill to the tippy top - another hundred or two hundred feet of elevation. I plodded along; he anteloped. Then, at the very top, he said "headache out of nowhere" and we descended back to the car much more slowly. My only symptoms were being a bit out of breath - I commented that it was like being on the elliptical. He had increasing headache pain concentrated around the back of his head and became miserable. I knew the only cure was water and lower altitude. 20 minutes later, we were below 9,000 feet, and it was as if it had never happened to him. I really didn't feel much different at all.
Neither of us lost any kind of "useful consciousness." But I know this isn't the same as being at effectively 8,000 feet and moving to 35,000 feet in a matter of minutes or seconds (but with supplemental oxygen immediately available).