In the USA (and other countries) how do pilots performing aerobatic displays above high-elevation airfields set their altimeters?
Discorde,
The same way as everyone else - they use the current Altimeter Setting (QNH* to you) and then convert all their gate heights to the appropriate altitude.
Of course, sometimes pilots get it wrong:
Just out of interest, I checked the Winter altimeters in my club’s two-week old ASK21B. With the field elevation of 3700’ set, the sub-scale read 1020 mb. I then made 43 twists of the knob to bring the altitude to 0’ and the sub-scale read 997 mb. I was surprised I was able to do this. Last time I tried this many years ago on an old US altimeter, I ran out of sub-scale.
The observant will notice I used mb rather than inches. This is because our glider was delivered with European altimeters! We shall be having words with the factory!
Using the Altimeter Setting doesn’t seem to cause any problem for new pilots. Our students have no difficulty figuring out that the downwind leg starts at 4500’ (800’ AGL).
* I would guess that 99% of North American light plane pilots would have no idea what QNH, QFE or any of the Q codes are.