Pacific
Topic Author
Posts: 1043
Joined: Fri Mar 10, 2000 2:46 pm

Unpressurised Aircraft At 20,000ft

Tue Jan 27, 2009 6:50 pm

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?
 
DaBuzzard
Posts: 66
Joined: Fri Sep 07, 2007 6:11 am

RE: Unpressurised Aircraft At 20,000ft

Tue Jan 27, 2009 7:11 pm

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.
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Unpressurised Aircraft At 20,000ft

Tue Jan 27, 2009 7:44 pm

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 :-)
 
JoeCanuck
Posts: 3948
Joined: Mon Dec 19, 2005 3:30 am

RE: Unpressurised Aircraft At 20,000ft

Tue Jan 27, 2009 9:56 pm

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...?
 
DashTrash
Posts: 1266
Joined: Mon Aug 21, 2006 8:44 am

RE: Unpressurised Aircraft At 20,000ft

Tue Jan 27, 2009 10:34 pm

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

Those old radials are all supercharged.
 
Mir
Posts: 19093
Joined: Mon Jan 05, 2004 3:55 am

RE: Unpressurised Aircraft At 20,000ft

Wed Jan 28, 2009 4:28 am



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
 
sccutler
Posts: 5567
Joined: Thu Jan 27, 2000 12:16 pm

RE: Unpressurised Aircraft At 20,000ft

Wed Jan 28, 2009 5:00 am

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 avatar
Starlionblue
Posts: 17087
Joined: Fri Feb 27, 2004 9:54 pm

RE: Unpressurised Aircraft At 20,000ft

Wed Jan 28, 2009 5:26 am



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." - John Ringo
 
User avatar
NWOrientDC10
Posts: 1283
Joined: Sun Mar 06, 2005 12:18 pm

RE: Unpressurised Aircraft At 20,000ft

Wed Jan 28, 2009 6:12 pm

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
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Unpressurised Aircraft At 20,000ft

Wed Jan 28, 2009 7:38 pm



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 :-)
 
Pacific
Topic Author
Posts: 1043
Joined: Fri Mar 10, 2000 2:46 pm

RE: Unpressurised Aircraft At 20,000ft

Thu Jan 29, 2009 7:57 am

Thanks to everyone for the very informative replies!
 
iRISH251
Posts: 622
Joined: Fri Nov 26, 2004 3:56 am

RE: Unpressurised Aircraft At 20,000ft

Thu Jan 29, 2009 7:32 pm



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.

Who is online

Users browsing this forum: No registered users and 17 guests