Definition
A navigation aid used on an instrument landing system (ILS) approach, consisting of a low-power non-directional beacon (NDB) installed at the same site as the outer marker. It allows the pilot to home to the outer marker position using ADF and also receive the outer marker's audio and visual signal as the aircraft passes overhead.
Plain English
A small radio beacon placed at the outer marker of an ILS approach. Pilots can fly toward it using their ADF, and as they pass over it, the outer marker tone and light confirm their position on the approach.
Context Anchor
Seen on instrument approach charts and used during instrument approaches to runways served by an instrument landing system.
Derivation
Locator' is used here in the sense of helping the pilot locate or home in on a specific point — the outer marker. The term combines the function of an NDB (which a pilot can track to) with the position-fixing role of the outer marker.
Why Pilots Care
It marks the final approach fix so pilots know they are at the correct altitude and position before descending on the glide slope.
Intuition Check
Do not picture a painted sign or physical marker outside the airport. In this term, the marker is an instrument-approach position identified by radio signals, and the locator is the radio beacon associated with it.
Example Sentence 1
The approach chart showed the LOM five miles outside the runway threshold, so the crew tracked the NDB inbound to intercept the localizer.
Example Sentence 2
ATC cleared the flight direct to the LOM for the ILS approach.