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
CodeMeaningSample use
QFEAtmospheric 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 hectopascals
QFFAtmospheric pressure at a place, reduced to MSL using the actual temperature at the time of observation as the mean temperature.
QNEIndicated altitude at the landing runway threshold when 1013.25 hPa or 29.92 inHg (atmospheric pressure at sea level in the International Standard Atmosphere) is set as altimeter setting. This would be done at aerodromes at high altitudes where setting of a QFE would not be possible.
QNHAtmospheric 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
CodeMeaningSample use
QDMMagnetic bearing to a station(callsign) request QDM (callsign)[1]
QDLSeries of bearings taken at regular intervals
QDRMagnetic bearing from a station(callsign) request QDR (callsign)[1]
QFUMagnetic bearing of the runway in useRunway 22 in use, QFU 220[2]
QGEDistance
QGHControlled Descent through Clouds (Royal Air Force use)
QTETrue bearing/track from a station(callsign) request QTE (callsign)[1]
QTFPosition in relation to a point of reference or in latitude and longitude
QUJTrue bearing/track to a station
Radio Procedures
CodeMeaningSample use
QGHcontroller-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
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