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Old 26th Jun 2009, 10:22
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smithgd
 
Join Date: Dec 2002
Location: Hampshire, UK
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Renard
You said.......The altimeters in my plane are calibrated for the standard atmosphere i.e. 27mb/100 feet.

Is that correct given in the standard atmosphere it varies?

Is 27ft/mb considered to be an ISA lapse rate for all altitudes?

So given the following info:
Aircraft at FL180
QNH = 1025mb

Using 27ft/mb (ISA lapse rate?) gives an altitude of 18,324ft AMSL.
Using 48ft/mb (Calculated lapse rate at 18000ft) gives an altitude of 18,576ft AMSL.

cheers
smithgd
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