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Unpressurised Aircraft At 20,000ft  
User currently offlinePacific From Hong Kong, joined Mar 2000, 1073 posts, RR: 0
Posted (5 years 10 months 6 days 13 hours ago) and read 4998 times:

I've been looking at the specifics of some propeller aircraft recently and noticed that unpressurised props have rather high certified ceilings. While Wikipedia is hardly a reliable source, the DC-3, Pilatus PC-3 Porter and the Twin Otter aircraft have service ceilings far exceeding 20,000ft.

How does high altitude flying work with these aircraft?
1. Do pilots need to use supplementary oxygen?
2. Are there heating systems on such aircraft or do pilots brave the cold?

11 replies: All unread, jump to last
 
User currently offlineDaBuzzard From Canada, joined Sep 2007, 136 posts, RR: 0
Reply 1, posted (5 years 10 months 6 days 13 hours ago) and read 4983 times:

1: Yes. Would not be good to have the flight crew taking a nap  Smile

2: As a rule, yes. At the very least you need to keep the windshield clear of ice / mist.

Higher altitude = lower fuel burn, and may allow you to take advantage of wind to further stretch your range.


User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 2, posted (5 years 10 months 6 days 13 hours ago) and read 4950 times:

Also, under current US FARs, you cannot take the aircraft any higher than a cabin altitude of 15,000 feet if you are carrying passengers (well, unless you want to give the pax supplemental O2...)  Smile

If those big Wright Cyclone radials on a DC-3 are anything like non-turbocharged GA flat piston engines, I'll bet their power output drops off significantly at FL200...  Wink Also, with turbocharged GA piston engines, at high altitudes, the lower volume of air through the air cooling fins in the engine jugs starts to become a factor (not an insurmountable one, just one that creates limitations, like having to keep an eye on CHTs and oil temperatures during climbs...). I don't know round engines, though (other than they sound incredibly cool and create great noisy oily starts  Cool ) .



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5478 posts, RR: 30
Reply 3, posted (5 years 10 months 6 days 10 hours ago) and read 4850 times:

Under certain circumstances, supplemental oxygen is required for flight starting at above 10.500 feet.

WWII flyers flew unpressurized in the mid to high 20's...with oxygen...and lots of warm clothing.



What the...?
User currently offlineDashTrash From United States of America, joined Aug 2006, 1550 posts, RR: 2
Reply 4, posted (5 years 10 months 6 days 10 hours ago) and read 4829 times:

I've flown a T210 into the mid 20s unpressurized on the mask.

Those old radials are all supercharged.


User currently offlineMir From United States of America, joined Jan 2004, 21804 posts, RR: 55
Reply 5, posted (5 years 10 months 6 days 4 hours ago) and read 4714 times:



Quoting Pacific (Thread starter):
1. Do pilots need to use supplementary oxygen?

Yes. Above 14,000 feet they need to be on oxygen full-time, and above 18,000 they have to be wearing masks - canulas won't cut it.

Quoting Pacific (Thread starter):
2. Are there heating systems on such aircraft or do pilots brave the cold?

Heaters are very common even on small GA planes. The Cessna 172 has a heater that's quite effective once the engine gets warmed up a bit.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineSCCutler From United States of America, joined Jan 2000, 5583 posts, RR: 28
Reply 6, posted (5 years 10 months 6 days 3 hours ago) and read 4696 times:

My plane has s ervice ceiling of 18,000', but it is normally aspirated; the turbocharged variant is certified to 26,600.

I do not routinely cruise above 12,000', and would never do so without O2.



...three miles from BRONS, clear for the ILS one five approach...
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17118 posts, RR: 66
Reply 7, posted (5 years 10 months 6 days 3 hours ago) and read 4678 times:



Quoting Pacific (Thread starter):
2. Are there heating systems on such aircraft or do pilots brave the cold?

For extra fun, imagine the WWII side gunners on a B-17, firing out of an open windows. COOOOOLD!



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineNWOrientDC10 From United States of America, joined Mar 2005, 1404 posts, RR: 4
Reply 8, posted (5 years 10 months 5 days 14 hours ago) and read 4532 times:
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Something else which should be considered are the physiological effects of trying to operate an a/c at high altitudes without cabin pressurization.

Three Canadian Armed Forces members participated in a "High Altitude Indoctrination" training program as referenced here:

http://www.cmaj.ca/cgi/content/full/169/8/803

Decreased pressure stress can result from nonpressurized flight, from loss of cabin pressure in pressurized aircraft, with work in hypobaric chambers and with extravehicular activities in space.

About 6 hours after the end of HAI training, the 3 patients boarded a commercial flight from Winnipeg to Vancouver (at sea level). During the flight, which lasted just over 3 hours, patient A experienced knee pain, which became severe and progressed to his hips, back, shoulders, elbows and neck. Patient B noted chest discomfort followed by numbness in his left arm and difficulty breathing. Patient C experienced retrosternal chest pain followed by back pain, headache, shortness of breath and bilateral tingling in his calves; he also had trouble swallowing and speaking for 20 minutes during the flight.

DCI following high-altitude exposure is rare but has a presentation similar to that of DCI due to other causes.

According to the information, simply being in a low pressure environment can have negative physiological consequences.

Good Day  Smile

Russell



Things aren't always as they seem
User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 9, posted (5 years 10 months 5 days 13 hours ago) and read 4494 times:



Quoting Starlionblue (Reply 7):

For extra fun, imagine the WWII side gunners on a B-17, firing out of an open windows. COOOOOLD!

IIRC, the waist gunners had electrically heated flight suits which plugged into the plane at their station that they wore, along with fur-lined flight jackets and boots (all marginally effective, from what I understand  Wink ). I've seen the B-17 crew provisions before in museums...

And some of the highest bombing runs (like the infamous Dresden ball bearing plant bombings) were conducted at 30,000 feet (!).



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlinePacific From Hong Kong, joined Mar 2000, 1073 posts, RR: 0
Reply 10, posted (5 years 10 months 5 days ago) and read 4331 times:

Thanks to everyone for the very informative replies!

User currently offlineIrish251 From Ireland, joined Nov 2004, 981 posts, RR: 4
Reply 11, posted (5 years 10 months 4 days 13 hours ago) and read 4183 times:



Quoting KELPkid (Reply 9):
And some of the highest bombing runs (like the infamous Dresden ball bearing plant bombings) were conducted at 30,000 feet (!).

Dresden was not a ball-bearings target - you may be thinking of Schweinfurt.


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