Radial vs course in aviation explained: see why VOR radials run from the station, how inbound reciprocals work, and how to read TO/FROM.
In aviation navigation, a radial is a magnetic bearing extending outward from a VOR station, always named for the direction from the station. A course is the direction of the path an aircraft intends to fly over the ground. The distinction is the same in real-world flying and flight simulators.
Radial vs course at a glance
The simplest distinction is that a radial identifies a line from a VOR, while a course identifies the direction you intend to travel.
| Term | What it describes | Example |
|---|---|---|
| Radial | A magnetic bearing extending from a VOR, based on the station’s north reference | The 090 radial is the half-line east of the station |
| Course | The intended direction of a path across the ground | Course 270 means travelling west along the selected path |
A radial does not reveal which way the aircraft is moving. An aircraft on the 090 radial could be flying towards the station, away from it or crossing the radial at any angle.
How do inbound and outbound courses relate to a radial?
An outbound VOR course normally has the same number as its radial, while an inbound course is the reciprocal.
- Flying eastbound away from the station on the 090 radial uses an outbound course of 090.
- Flying towards the station from the 090 radial uses an inbound course of 270.
- Flying towards the station from the 270 radial uses an inbound course of 090.
To find the reciprocal, add or subtract 180°. A useful mental shortcut is to add 2 to the first digit and subtract 2 from the second, or vice versa: 090 becomes 270, while 320 becomes 140.
A course can continue through the station. If you fly course 090 from west to east, you approach on the 270 radial and depart on the 090 radial. The course remains 090, but the indicator changes from TO to FROM during station passage.
What does the OBS select on a VOR indicator?
The OBS selects a course, although pilots sometimes informally describe this as selecting a radial.
- Choose the intended course. For outbound flight, this normally matches the radial; for inbound flight, select its reciprocal.
- Check the TO/FROM indication. TO means the selected course is oriented towards the station; FROM means it is oriented away from it. It does not prove that the aircraft itself is moving in that direction.
- Interpret the CDI. The needle shows displacement from the selected course line. It is not a turn command unless the intended course has been set and the aircraft is flying a sensible intercept.
- Apply wind correction. Adjust heading as required to keep the CDI centred rather than repeatedly chasing the needle.
Setting the reciprocal course by mistake produces confusing or reversed-looking CDI indications, commonly called reverse sensing. Near the VOR, CDI movement may also become rapid or unreliable during the cone of confusion. Our guide to practical VOR and NDB navigation in flight simulators covers interception and tracking technique.
Is course the same as heading or track?
Course, heading and track describe different things, even when their numbers happen to match.
- Course is the intended path direction over the ground.
- Heading is the direction the aircraft’s nose points.
- Track is the aircraft’s actual path over the ground.
- Radial identifies the aircraft’s line or position relative to a VOR.
With a crosswind, the heading must differ from the course to hold the required track. We explain that distinction further in our guide to course, heading and wind correction.
Is a radial the same as a bearing?
A radial is a specific type of bearing measured from a VOR station, whereas bearing is a broader term that can describe direction to or from any point.
If an aircraft lies on the 090 radial, the magnetic bearing from the VOR to the aircraft is 090; the bearing from the aircraft back to the VOR is approximately 270. This reciprocal relationship assumes both values use the same magnetic reference.
Published VOR radials use the station’s calibrated magnetic reference, which may not exactly match the magnetic variation used by another instrument or navigation database. NDB navigation also uses bearings to and from the beacon, but calling them VOR radials is normally incorrect.