Radio Navigator
Glossary

QDM and QDR

Direct answer

QDM is the magnetic bearing TO a station. QDR is the magnetic bearing FROM it. The two are always reciprocals of each other.

Also written as: Q-codes, QDM QDR difference.

These are surviving Q-codes from radiotelegraphy, and they persist because they are unambiguous in a way that "bearing" is not. QDM points at the station: it is the magnetic track you would fly, in nil wind, to reach it. QDR points away from it, and is therefore identical in meaning to a VOR radial.

The pairing matters most around holds and intercepts, where a procedure is described relative to the fix rather than relative to you. If a hold is described by its inbound QDM and you are given a QDR to intercept, converting between them is simply adding or subtracting 180.

Where this comes up

Sources

  1. ICAO Doc 8400, Procedures for Air Navigation Services: ICAO Abbreviations and Codes. Defines the Q-code set, including QDM and QDR.
  2. FAA Aeronautical Information Manual, Section 1-1-3 (VOR). Magnetic bearing conventions to and from a station.

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This article does not constitute flight instruction. Always defer to the guidance of your qualified flight instructor and to current charts and procedures or regulations published by your country's aviation authority.

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