So what have we established? In extreme temperatures, either low or high, there can (and most likely will) be a discrepancy or deviation or difference between the real altitude and the altitude shown on the altimeter, even if set to the correct QNH.
Q1: how to determine said discrepancy?
Q2: why don't we fly to GPS altitudes? That would allow us to do away with the cumbersome QNH comm's and settings, including the (by some) hated regional QNH.
A2a: because all the procedures would have to be rewritten
A2b: because certain smart-asses would have less opportunity to show off
A2c: because it would make it harder to find 20 good complicated questions for the PPL theory exam
Last edited by Jan Olieslagers; 24th Jul 2016 at 07:50.