Originally Posted by
island_airphoto
Having the altimeter read AGL would mean it would be jumping all over the place over any kind of hilly terrain and make traffic control impossible.
Do you mean that airfield QFE settings vary across hilly terrain —yes of course they do. It’s difficult to tell, but maybe you meant that altimeters set to a QFE fluctuate wildly when flying over hilly terrain—which is complete nonsense! Barometric Altimeters are sensitive to the pressure (or ‘weight’) of the atmospheric column of air above them, not below them.