Aeronautical Code signals

The Aeronautical Code signals are radio signal codes. They are part of a larger set of Q Codes allocated by the ITU-R. The QAA–QNZ code range includes phrases applicable primarily to the aeronautical service,[2] as defined by the International Civil Aviation Organisation.

First defined in ICAO publication "Doc 6100-COM/504/1" in 1948 and in "ICAO Procedures for Air Navigation Services, Abbreviations and Codes (PAN a S-ABC)" [Doc8400-4] (4th edition 1989), the majority of the Q codes have slipped out of common use; for example today reports such as QAU ("I am about to jettison fuel") and QAZ ("I am flying in a storm") would be voice or computerized transmissions. But several remain part of the standard ICAO radiotelephony phraseology in aviation.

Altimeter settings

Code	Meaning	Sample use
QFE	Atmospheric pressure at a specified datum such as airfield runway threshold. When set, the altimeter reads the height above the specified datum.	Runway in use 22 Left, QFE 990 millibars
QFF	Atmospheric pressure at a place, reduced to MSL using the actual temperature at the time of observation as the mean temperature.
QNE	Atmospheric pressure at sea level in the International Standard Atmosphere (ISA), equal to 1013.25 mbar or hPa and used as reference for measuring the pressure altitude. When flight levels are used as an indication of altitude, 1013.25 hPa is used as mean sea level (QNH).
QNH	Atmospheric pressure at mean sea level (may be either a local, measured pressure or a regional forecast pressure (RPS)). When set on the altimeter it reads altitude.	Request Leeds QNH

Radio Navigation

Code	Meaning	Sample use
QDM	Magnetic heading to a station	(callsign) request QDM (callsign)[1]
QDL	Series of bearings taken at regular intervals
QDR	Magnetic bearing from a station	(callsign) request QDR (callsign)[1]
QFU	Magnetic bearing of the runway in use	Runway 22 in use, QFU 220[2]
QGE	Distance
QGH	Controlled Descent through Clouds (Royal Air Force use)
QTE	True bearing from a station	(callsign) request QTE (callsign)[1]
QTF	Position in relation to a point of reference or in latitude and longitude
QUJ	True heading to a station

Radio Procedures

Code	Meaning	Sample use
QGH	controller-interpreted DF let-down procedure, on UHF or VHF[3]

References

1. CAP 413 Radiotelephony Manual 21 2 complete.pdf Archived May 8, 2014, at the Wayback Machine., p.12
2. QFU on The Free Dictionary
3. QGH on The Free Dictionary