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Posts: 3053
Joined: Sun Jan 28, 2001 2:24 pm

Coldest Outside Air Temperature At Altitude

Thu Jan 15, 2004 1:29 am

I came across this pic and the caption got me to thinking. . .just what are some of the lowest outside air temps when flying at altitude (for airliners). I would venture to guess that Concorde recorded the lowest, for an airliner, but what about the no-supersonic a/c?

I've also heard that the lowest "at-altitude" temps occur over the Pacific. . .any truth to that?

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RE: Coldest Outside Air Temperature At Altitude

Thu Jan 15, 2004 3:16 am

In the standard atmosphere, 216 K or -57 degrees Celsius, between 11,000 FL360) and 25,000 (FL820) meters absolute altitude ASL.

The atmosphere is usually non-standard so you're bound to see lower readings at times, but that's the neighbourhood.

I thought I was doing good trying to avoid those airport hotels... and look at me now.

RE: Coldest Outside Air Temperature At Altitude

Thu Jan 15, 2004 3:38 am

The coldest OATs that I have encountered were generally around tropical and equatorial areas. It sometimes happens to be at STD - 20 degrees C... I have seen the OAT at some -70 C and was seriously concerned about fuel heat for our tanks... our fuel has to remain above - 37 C... By chance, we do not assume OAT as been the limiting factor, but the RAT (or TAT) which is some 30 degrees warmer than OAT in cruise at Mach 85...
Since the temperature lapse rate is supposed to stabilize when reaching 36,089 feet, at a value of -56.5 C, the tropopause is much higher in these areas of the globe, the result is that you might be at 41,000 and still below the tropopause...
Same thing in reverse over polar areas... I have flown a few times at latitudes of 85 N, or straight over the South Pole... it is generally "warmer" over the poles, because the tropopause is often as low as 28,000 feet...
So a good thing to remember (and a "trick" question) -  Big grin
What is the coldest tropopause...?
Polar tropopause...?
Tropical tropopause...?
If you think of Polar bears, you are wrong...
The correct answer is that it might be right over... Central Africa...
Happy contrails -
(s) Skipper
Time to go back to the beach and enjoy a cold "Brahma"...