Definition
A low-power, low- or medium-frequency non-directional radio beacon installed in conjunction with an instrument landing system (ILS), used as an aid to final approach. A locator usually has an average radius of coverage of between 10 and 25 NM and is typically co-located with the outer or middle marker of the ILS.
Plain English
A small radio beacon placed near an ILS approach so pilots can home in on it during the final part of the approach. It does not give precise guidance on its own — it just helps the aircraft find and line up with the ILS.
Context Anchor
Seen on instrument approach charts and in approach procedures that use older ground-based radio navigation aids.
Derivation
From the Latin locare, 'to place.' The beacon's job is to help the pilot 'locate' the final approach course leading to the runway.
Why Pilots Care
Provides reliable bearing information during instrument approaches when visibility is low and other navigation aids may be limited.
Intuition Check
Locator does not mean any device that finds something. In this FAA use, it means a specific ground radio beacon used to help identify a place on an instrument approach.
Example Sentence 1
The approach plate showed a locator co-located with the outer marker, so the crew tuned the ADF to identify it before commencing the ILS.
Example Sentence 2
On the ILS approach the crew used the locator to establish the initial approach fix before intercepting the localizer.