Definition
A cockpit instrument that combines a magnetic compass card with one or two needles that point directly to the station being received by an ADF (automatic direction finder) and/or a VOR (VHF omnidirectional range) receiver. The compass card rotates with the aircraft's heading, so the needle indicates the magnetic bearing from the aircraft to the station, with the tail of the needle showing the bearing from the station.
Plain English
An instrument with a rotating compass face and one or two needles that always point toward a selected ground-based radio station, telling the pilot which direction the station lies relative to the aircraft.
Context Anchor
Seen on aircraft instrument panels, especially in instrument navigation, when a pilot is using radio navigation signals to maintain position awareness or navigate toward a selected source.
Derivation
Radio (because the needle is driven by signals from a ground radio station) plus magnetic (because the rotating card is referenced to magnetic north) plus indicator (a display). The name describes exactly what it does: shows where a radio station is, referenced to magnetic direction.
Why Pilots Care
Gives immediate visual bearing information that reduces cockpit workload and helps maintain accurate courses to or from navigation stations.
Intuition Check
Do not read “magnetic” as meaning the needle is physically attracted to the radio station. Here it means the heading and bearing are shown using magnetic north as the direction reference.
Example Sentence 1
The pilot glanced at the RMI and saw the needle pointing to the right, confirming the VOR station was off the right wing.
Example Sentence 2
With the RMI set to the VOR, the needle showed a 30-degree relative bearing that matched the desired intercept angle.