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Old 20th June 2002 | 18:37
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Eagle1
 
Joined: Jan 2001
Posts: 14
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From: Amsterdam, Holland
Cool Qnh?

Hi all,

Just started studies for my JAR-CPL, and one of the first subjects we tackled was altimetry. Basically it's all clear - and most of it was PPL-stuff anyway, except for the temp. corrections - but there is one little question that puzzles me.

There we go: when QNH is given, I read anywhere that QNH is basically a calculated pressure level (which might have to do with the temperature corrections). I always thought that QNH was the actual pressure level at sea level, but indeed, when you start correcting for non-standard temperature, your QFE might be wrong.
So, is QNH basically the real, actual pressure level, without temp. corrections taken into account, or is it indeed a calculated level, so with temp. corrections your airfield level is indeed the level you see on your altimeter? What's practice?

Hope for an answer, thanks.
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