- Mar 9, 2010
Firstly, it's simply the rule in most countries. Russia is an exception, using QFE below 5000.Why not?. Customary?
Altitude above field elevation of zero sounds more logical unless there are other reasons for QNH
It does have it's uses. For instance, if you're doing aerobatic display flying, half way through a loop isn't the time to be trying to add airfield elevation to get your entry gate.
But, it causes issues with separation, as you'll need to work out how you're going to keep aircraft that aren't coming to a particular airport separate from ones going somewhere else, or in a go around. Local hills are also an issue, as you'll need your charts to give the terrain height differently for each local airport. It would be a nightmare at places like LA, where you have local very high terrain, and multiple airports, all at different elevations. Imagine a go around, where you need to fly QFE for the approach, QNH for the go around, and then back to QFE. All at low level, in a busy environment.