QFE is a three letter acronym which can have meanings in aviation, in software development, and in internet usage.

Aviation acronym

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QFE is a Q code used by pilots and air traffic control (ATC) to refer to the barometric altimeter setting which will cause an altimeter to read height above the official reference datum for a particular airfield (generally the height of a particular runway threshold). An altimeter set to QFE will therefore read zero when on the ground at the beginning of the runway.

QFE is just one of many aviation Q codes. Originally, when the only method of communiction was by Morse code the Q codes ran from QAA to QZZ, each code could be decoded by a radio operator onboard an aircraft or in an ATCU by reference to the code book. The letters of the code do not in themselves stand for anything. The letter Q (--.-) was used to attract the attention of the radio operator to the following two letter coded message as it was "easy" to hear (da da de da) and not used often in normal "speech". The use of Q codes saved much time, for instance, instead of a radio operator sending the message "To what pressure setting must I set the subscale on my altimeter so that it reads zero on touchdown at your airfield?", he would simply send "QFE".

In modern aviation only a few of the most frequently used old Q codes are still used/remembered, eg.:

QFE - subscale setting to give height above aerodrome,

QNH - subscale setting to give altitude above sea level,

QNE - value indicated on altimeter at touchdown when a subscale setting of 1013 millibars (a standard atmospheric pressure setting used to fly Flightlevels) is set,

QDM - the magnetic bearing to a position,

QDR - the magnetic bearing from a position,

QTE - the true bearing to a position,

QUJ - the true bearing from a position,

QSY - change frequency to,

QFU - the precise magnetic heading of a runway,ie, the QFU of runway 24 is 238 degrees.

Student pilots sometimes think of QFE as "Q Field Elevation" to help them remember its meaning.

ATC will update pilots with the QFE when necessary. A typical radio conversation might go:

• Pilot: Golf Whiskey Alpha Charlie Foxtrot, requesting taxi clearance for local VFR.
• ATC: Golf Charlie Foxtrot, taxi to Alpha for two-five right hand, QFE niner-niner-eight millibars.
• Pilot: To Alpha, two-five right, QFE niner-niner-eight, Golf Charlie Foxtrot.

Here, the pilot of G-WACF (who is on the ground) requests a taxi clearance and is told to taxi to holding point A for runway 25, the circuit is right-handed and QFE is 998 millibars. The pilot acknowledges the information by reading it back to ATC.

In most parts of the world, QFE is given in millibars (or hectopascals, which is the same-sized SI unit). Whilst the Royal Air Force (RAF) and some European private pilots still use QFE, it is largely obsolete in commercial aviation, where QNH is preferred for take off and landing (and where sophisticated radio aids can be used during landing). In general aviation, QFE is routinely used during take off and landing (where the eyeball tends to be used) and when flying in the circuit. The exception to this is in the USA and Canada, where QFE is rarely used, the most common practice being to use QNH (known simply as the "altimeter setting") for all operations below the transition altitude.

Software development acronym

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QFE stands for Quick Fix Engineering. This is the Microsoft and Intel term for a 'Bug patch' or as it was previously known, a 'Hotfix'. Many software modules related to Microsoft products return a QFE number indicating a patch number in the version/build information. QFEs are often bundled together to make a 'Service Pack'.

Internet acronym

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QFE is also a popularly used internet forum acronym for "quoted for emphasis".

Networking hardware acronym

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QFE stands for Quad FastEthernet and is a type of vendor-specific network card with four network interfaces.

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