QNH Atmospheric Pressure HPa


All the time, at all airports, at any altitude from 0 ft to FL430, the atmospheric pressure at Infinite is always 1013HPa, or is it the current “METAR” pressure in the real world?

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Hmm. The pressure is definitely there, because if you fly at 230kts at 45,000ft your ground speed would be 520kts.

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I stand to be corrected… but I believe the answer is neither.

My understanding is the whole world is set to a single (accurate yet generic) QNH… ie if an airfield elevation is 100ft, you will see 100ft on the ground there etc. And there are no pressure differences around the globe on IF.

Which would technically mean there are no flight levels, as flight levels are based solely off 1013. Transition level is around 3-6000ft (yes I know it’s higher elsewhere) and I’ve never seen the altimeters switch on the way up or down.

As mentioned at the start, I’ve never really looked into it so could well be wrong 😊


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