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When is QFE, instead of QNH, used for the altimeter setting?

QFE: If you set the subscale of your altimeter to read ... millibars, the instrument would indicate its height above aerodrome elevation (above threshold, runway number ...).—Wikipedia

It seems like a good setting for flying in Class G, as the pilot would get height above ground level near the reporting station.

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    $\begingroup$ Be aware though, setting to QFE your altimeter will read the height above ground at the point the QFE measurement was taken. Terrain changes rather quickly so I would not say that this is your true AGL, its simple the height above the measurement. $\endgroup$ – Ron Beyer Aug 26 '16 at 13:21
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    $\begingroup$ There are multiple possible answers... likely contradictory from one country to the other. Simply said QFE is equivalent to height above measuring station at the time of the measure, not altitude. Quite handy for traffic pattern, but dangerous to fly over an extended area, as all aircraft may not use the same value, so they won't have the same altitude reference. $\endgroup$ – mins Aug 26 '16 at 16:55
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It is used in aerobatic competition.

It is much safer and easier to read AGL altitude directly from the altimeter than to attempt to do the arithmetic immediately prior to performing a maneuver.

I normally fly out of a field at an elevation of 1000'. If I were to fly a contest in Colorado where field elevation is 8000' or higher, my altimeter will show an unusually high reading even when I'm still on the ground.

If I reset to QFE I still have to deal with density altitude considerations but at least I will have unambiguous altitude information.

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    $\begingroup$ It is also commonly used by gliders. $\endgroup$ – Lnafziger Aug 28 '16 at 16:39
  • $\begingroup$ It is also used in all aviation below transition altitude in for example China and Russia. $\endgroup$ – Sami Jul 19 '18 at 18:00
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In the UK at least, QFE is used primarily by the military. There are still a number of airfields which are used by both the military and civilian flights (eg, RAF Northolt) and flying in there you will be given a QFE.

As a civilian pilot, you are only likely to be given a QFE on joining to land at an airfield, and while in the circuit.

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In the UK, General Aviation traffic typically uses QFE in the circuit, and regional QNH in the cruise.

From Pooleys Air Navigation Manual: "It is very convenient for circuit operations if the altimeter can be set to indicate height above aerodrome level (aal). This means that a 1,000ft circuit at, for example, Leicester airfield (elevation 469 ft) can be achieved with the altimeter indicating 1,000 ft rather than 1,469 ft if QNH was set in the subscale. It is a satisfactory procedure in the UK to set QFE in the subscale when flying in the circuit".

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