In the UK the Aerodrome QFE is based on the Aerodrome elevation - ie the highest point on the manoeuvring area.
A threshold QFE is passed, in the case of an instrument runway, when the touchdown elevation is 7 feet or more below the aerodrome elevation.
Other States may have different criteria. Last time I looked in Greece the QFE is based on the elevation of the aerodrome reference point (usually about the middle of the main runway).
Regarding the QFE/QNH debate which is almost as old as aviation itself, having used both I definitely prefer QNH - far less winding on the altimeter and it breeds a lot more awareness of terrain elevation. Having seen many an altitude bust in the sim on Go Arounds when QNH has been set late (especially at higher elevation airports) or not at all, I think this is yet another reason for QNH operation.
That said what is really important is that the altimeters are being managed correctly whatever system you are using.
Also the altimeter tolerance check prior to flight should always be conducted on QNH (and not QFE) - the UK AIP lists apron elevations specifically for this purpose. At the general aviation level I have seen many a pilot attempt to conduct the altimeter tolerance check on QFE only to discover it is outside the prescribed limits because of the difference in elevation between the aerodrome elevation (assuming aerodrome QFE in this case) and the actual elevation of where the aircraft is standing. This is further compounded by some AG/FIS who only pass QFE when pilots ask for taxi and state their detail is circuits. They dont seem to understand that you need the QNH to check the altimeter for tolerance even if you are subsequently going to set QFE whilst in the circuit!!
Last edited by fireflybob; 11th January 2005 at 23:22.