Radio Navigator
Glossary

Radial vs course

Direct answer

A radial is a magnetic bearing measured FROM a VOR station; a course is the track you select on the OBS and intend to fly. They are the same number outbound, and reciprocals inbound.

Also written as: radial or course, OBS setting.

Radials belong to the station. The 090 radial is the line running due magnetic east from the VOR, and it stays the 090 radial no matter which way you are flying along it. The course you set on the OBS belongs to you: it is the track you intend to make good relative to that station.

The two numbers coincide only when you are tracking outbound. Tracking the 090 radial outbound, you set 090 and expect a FROM indication. Tracking that same radial inbound, you are flying west, so you set the reciprocal, 270, and expect a TO indication. Setting the radial value while tracking inbound is the classic reverse-sensing error: the needle then tells you to turn away from the course rather than toward it.

Where this comes up

Sources

  1. ICAO Annex 10 (Aeronautical Telecommunications), Volume I, Radio Navigation Aids. Defines VOR azimuth signal characteristics and the radial convention.
  2. FAA Aeronautical Information Manual, Section 1-1-3 (VOR). Course selection, TO/FROM sense and reverse sensing.

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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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