Unpressurised airliners and mountain ranges

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Unpressurised airliners and mountain ranges

Post by DavidK »

Hi all,

Haven't tried searching for info about this yet as I thought someone might know and/or be able to point me in the right direction -- I've been flying around South America recently and wondering how / where unpressurised airliners crossed mountain ranges such as the Andes... I've improvised two crossings at under 10,000 ft (here and here) though the second proved more iffy than I'd recommend. Meanwhile, the first necessitated a considerable detour -- perhaps that's what was done..?

David

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DaveB
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Re: Unpressurised airliners and mountain ranges

Post by DaveB »

HI David :hello:

It's difficult to nail this down with any certainty. While the aircraft was unpressurised and normal cruising done below 10000ft, some 'flying around' may have been the order of the day but the crew would have had oxygen so climbing above would, I reckon, also have happened. They would not have navigated through mountainous regions below 'peak' levels.. scenic but too dangerous :) Routing I have shows only direct routes.. point to point and this may not be accurate. The accident with Star Dust was due to her flying in 45mph winds which were gusting to 60mph. Sadly, she was not where she was supposed to be.

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Re: Unpressurised airliners and mountain ranges

Post by DavidK »

DaveB wrote:Routing I have shows only direct routes.. point to point and this may not be accurate.
I'm guessing it's not, as flying direct between Buenos Aires and Santiago or Lima and Maiquetia would surely mean at least 12,000+ ft...!
The accident with Star Dust was due to her flying in 45mph winds which were gusting to 60mph. Sadly, she was not where she was supposed to be.
That's something I now appreciate a little more, if only in a small way: after threading my way back across the Andes en route from Lima to Maiquetia, I emerged onto a seemingly endless and featureless plain (the "Santiago-Comaina Reserved Zone", on the southeast border of Ecuador) and almost switched to IFR, as I wasn't confident if, when or how quickly the LR deflection pointers would move. And that was in good flying conditions...

Thanks for your reply,
David

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Re: Unpressurised airliners and mountain ranges

Post by DaveB »

Hello Mate :hello:

These flights really were ground breaking in many ways and the BSAA crews were top flight ex-RAF.. experienced men with many hours on the type under their belts. The strong wind that blew them off course wasn't unheard of in the area but not widely known about and certainly not fully understood. Flimsy is best how to describe radio navaids in that part of the world. Often, pilots would call for a 'tone' and use DF equipment to confirm their position.
While the Lancastrian's cruise alt was generally below FL100 (7500ft ish plus and minus), there was terrain avoidance when necessary as 'Flying with the Stars' shows. The Star Dust crew were sure they were only 5mins away from Santiago when their last report was sent but they were obviously very much off course by then. Here are the last 5 reports sent..

15:07 33 55'S. 62 33'W. Height 10,000ft, course 286, speed 196kts, ETA Santiago 17:30

16:00 33 25'S. 65 30'W. Height 10,000ft, course 282, speed 196kts, ETA Santiago 17:30

17:00 32 50'S. 68 30'W. Height 20,000ft, ascending to 24,000ft, speed 194kts, ETA Santiago 17:43

17:33 ETA Santiago 17:45

17:41 ETA Santiago 17:45

The 17:41 report was the last thing heard. Seems amazing doesn't it that the crew were probably looking forward to a nice cool beer in the bar in a few mins time. A damn shame :(

There you go. While a low cruise alt was desirable for passenger comfort.. don't feel forced to stay low on your trips in that part of the world. Miss the lumpy bits at all costs ;)
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Re: Unpressurised airliners and mountain ranges

Post by Garry Russell »

I've tried to find something on the net, but failed. Years ago I was reading an article on Empire flying boats and there it said they sometimes went up to 20,000 on some routes.

Perhaps, if brief it's not too bad. Some WW1 fighters went up to 20,000 on patrols I doubt if they had oxygen...or did they???
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Re: Unpressurised airliners and mountain ranges

Post by DaveB »

Hello Mate :)

I'm not sure if the Lancastrians were fully kitted with oxygen. Certainly, the crew would have been 'on supply' when needed but I doubt this exended to the pax. Sadly, I can't find anything to confirm it one way or the other :| No real danger to the passengers at FL200 but you'd not want to keep them there longer than necessary :)

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Re: Unpressurised airliners and mountain ranges

Post by Garry Russell »

Hi Dave

Probably just up and over...The Empires had steam radiators so they could keep them warm. I was reading about that last night, water was boiled by the exhausts to extract steam for the rads. :lol: :lol:

My query on Oxygen was the WW1 fighter. The Lancastrian probably had it as standard for the crew, but a WW1 fighter??? *-)
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Re: Unpressurised airliners and mountain ranges

Post by DaveB »

Hello Mate..

I may be completely wrong but no.. I can't see it in a WW1 fighter. I doubt very much if the effects of oxygen starvation were well documented during the 14-18 war though it may well have been known about. You might even say they didn't know a lot about flying in the First World War let alone about the need for oxygen at altitude :)

EDIT: Just taking the WWI bit a tad further.. we all know the Sopwith Camel and what an ace fighter it was. Having had a quick read-up.. one of the main reasons it was dropped soon after the war years was it's lack of performance above 10000ft.. FL120 being tops or thereabouts so during the war.. they were still only teatering around the 10K mark :)

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Re: Unpressurised airliners and mountain ranges

Post by Chris Trott »

With modern aircraft, unpressurized flying above 10,000 feet isn't as uncommon as people think. You only need to provide the pax with oxygen above 14,000 feet and crew only has to go on oxygen when above 12,000 feet or over 10,000 feet for more than 30 minutes. As such, it's not as big of a deal as people think. If you acclimate prior to your flight, those limits are raised appropriately. For instance, the FAA gives an exemption to people who live in Colorado. If you live in Denver, you're allowed to fly for up to 30 minutes at 14,000 feet without oxygen only being required to go on oxygen when above 15,000 (although most pilots "fudge" this in the daytime) Passengers aren't required to have oxygen until 16,000 feet (if acclimated). I imagine that there are allowances in places like Chile where a lot of these guys live at 10,000 feet plus to fly up close to 18,000 feet without oxygen, although I doubt much above that as the air simply gets too thin for you to breath and keep full consciousness no matter how acclimated you are.

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Re: Unpressurised airliners and mountain ranges

Post by DavidK »

Thanks for all the input -- when I tried searching the Web for any information on this topic, this happened to be the first result. So, it sounds like flying BSAA across South America really might've been more adventure than transport.

When I revisit South America in the Lancastrian, I'll lift the cruising altitudes across the Andes by a few thousand feet. I reckon, though, I'll still need to fly the same kinds of detour as before, but no longer so close to the ground.

David

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