I saw something recently that stated that the reason commercial airlines don’t fly over the Himalaya Mountains is because in case of a sudden loss of cabin pressure, the pilots wouldn’t have the room to drop down far enough for passenger safety.
Not that I doubt the math of it but do planes suddenly lose cabin pressure enough for that to be a concern? Also don’t planes have about 20 minutes of oxygen in the drop down masks?
Questions, is the above true? Do *any *planes fly above the Himalayas? Are the Himalaya Mountains the only range too high to fly over?
Disclaimer: I know just about nothing regarding airplanes and less about the Himalayas.
The board’s commercial pilots can answer much more authoritatively than I can, but in the meantime:
You want to get out of danger as quickly as possible, and in my experience (as an engineer, not as a passenger or pilot) standard procedure is to dive down to ~10,000 feet ASAP. Most flights have >100 passengers, and the chances are pretty good that one of them has impaired lung function or another issue that makes high altitude a problem even with supplemental oxygen.
Also, if one or more of the oxygen generators or masks is defective—and remember, there are about 150 chances to find a defective one on every flight—that person may die if you dawdle at 35,000 feet.
I’d argue that oxygen generators/masks are there to help more people survive an immediate descent than they are to allow one to descend at one’s leisure.
And in the accounts I’ve read of sudden decompression, most passengers assume the steep dive is a result of the bang they just heard rather than a reaction to it. The dive is a lot steeper than people are used to, so people assume that the angle alone means terrible things.
Given all that, I can see how anything that impairs a steep dive to 10,000 feet could be taken as an unacceptable risk.
I have been on a commercial flight (Delta to be precise) which lost cabin pressure and had to quickly descend and go for an emergency landing. The O2 masks deployed.
The ear pain was really bad and all fellow travelers crying and praying made it really really bad but I remember the masks lasting more than 10 mins or so. My sense of time was distorted but it was definitely longer than 2 mins. More like 10 to 15 mins.
Oh and the angle of descent is very steep. It feels like you are in free fall.
After the incident, I got really scared every time there was turbulence on normal flights and it took me a good many years to get over it.
I have flown over the Himalayas
I have landed in the Himalayas
I also live in them so there is that.
The Himalayas are the meeting point of 3 nuclear powers, they are some of the most observed parts of the planet. Both the ground and the air space If you want to fly between India and China and Pakistan and China, you need to fly over them
The airport in Lukla, Nepal is about 9383 feet in altitude. What makes it so dangerous is that the landing strip is so short (1729 feet) and the runway incline is 12%. The planes land “up hill”. After the runway ends, the cliff drops about 2000 feet and there is a “wall” of mountain just on the other side of this cliff. After take off, the pilots make a sharp left turn to avoid hitting this mountain.
When I was there in the early 80’s, the runway was just a grass field, but it was paved many years ago now. The crashed aircraft from previous disasters on the side of the airfield was very comforting.Edmund Hillary’s wife was killed in a crash there.
I’ve seen a documentary about a landing with a jet plane in Lukla from the sight of the cockpit, the pilot commenting, on my regular 32" flat screen, and I felt very dizzy. You could give me all the money in the world but I wouldn’t fly there.
In my many years at Boeing, we have built quite a few 737’s for Air China and others just for flying the high mountain routes. All of these planes do not use traditional oxygen canisters for oxygen, all use gaseous oxygen. The aft cargo holds 12 large oxygen bottles for this purpose. They are designed to land at airports at more than 14,000 feet in altitude without deploying the oxygen system. All other commercial aircraft are designed to deploy oxygen masks at 14,000 feet. I hated working on these planes, a normal 737 takes about 30 minutes to test the oxygen system and restore the plane. The high altitude planes took 8 to 10 hours.
I was about to ask where all these fourteener airports are, and then I found this list. Well dayum. I know that excessive density altitude can occasionally require airports in the US to close; these would be airports at moderate altitude on extremely hot days, e.g. Phoenix Skyharbor. But wow, that’s gotta be interesting flying out of an airport that’s actually at 14K feet. Surely that air there on a normal day is thinner than Skyharbor on a hot day?
I didn’t think it was so much the density altitude was too high at Sky Harbor, but rather the exterior conditions were outside the hard numbers listed in the POH. (And I was told that extending the trend for an extra degree or two Fahrenheit was out of the question)
Density altitude calculator. Plugging in typical numbers for Daocheng climate yields a density altitude in excess of its already ridiculous altitude of 14,472 feet. I’m guessing lots of runway, a steely eye looking for V1 and V2, and not that much payload.
I used to live in Phoenix and I’ve flown out of the appropriately-named El Alto airport in Bolivia (13,300 feet). The takeoff run at El Alto was noticeably longer than any other I can recall, including at Sky Harbor on a hot day.
Gray Ghost has it: while density altitude is often a significant factor at Phoenix, the real issue is the maximum operating temperatures. Machine Elf’s link actually calls this out specifically: 118 is the max for many Bombardier regional jets. Many Boeings can go to about 125 degrees F.
Paro, Bhutan. Only 15 pilots are qualified to land here (according to the pilot in the video.)
ETA: I set the URL to start as they are getting ready for landing(I’d call it being on final approach, if it weren’t for the mountains they still have to dodge), about 3 minutes before touchdown, and a few seconds before the pilot starts praying.
Thanks, that must’ve been it. It wasn’t exactly the same footage I saw, but a different approach with a different pilot, but everything else looks familiar, especially the narrow valleys and the sharp right turn just before the landing.
From what I’ve read, they do fly over the Himalayas, but it involves more advance planning. They have to have a pre-planned route to follow during the decent in the event of a loss of cabin pressure, rather than simply descending straight ahead.