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 is for study. Follow the instructions from your qualified flight instructor. Use current charts, procedures, and the regulations from your aviation authority.

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