Definition
The omnibearing selector is the rotatable course-selecting knob and azimuth ring on a VOR indicator that lets the pilot choose which radial (magnetic bearing from the VOR station) they want to track. Turning the OBS rotates the compass-card scale (or moves a digital readout) until the desired course appears under the index, at which point the course deviation indicator (CDI) shows whether the aircraft is left, right, or on that selected course.
Plain English
It is the knob on the VOR instrument you turn to pick which course line, measured outward from the station, you want to fly. Once you set the course, the needle on the instrument tells you whether you are on it or off to one side.
Context Anchor
Seen when using a VOR navigation display during instrument flying or instrument training.
Derivation
Omni' comes from Latin 'omnis' meaning 'all', and 'bearing' is a navigation direction. So 'omnibearing selector' literally means 'a selector for any bearing' — reflecting that the pilot can dial in any of the 360 radials around the VOR station.
Why Pilots Care
Selecting the correct radial lets the pilot track a precise course to or from the station, which is essential for staying on airways and flying instrument approaches.
Intuition Check
Turning the OBS does not turn the airplane and does not tune the radio station. It only selects the course line that the navigation display will use for guidance.
Example Sentence 1
After tuning the VOR frequency, the pilot rotated the OBS to 270 to track the inbound course to the station.
Example Sentence 2
With the OBS set to the inbound course, the needle showed when the aircraft drifted left or right of the selected track.