Definition
A low-power, low- or medium-frequency (L/MF) radio beacon installed at the outer or middle marker of an instrument landing system (ILS), used by pilots with an automatic direction finder (ADF) to locate and track inbound to the marker as part of the ILS approach. Typical usable range is at least 15 nautical miles.
Plain English
A small radio beacon placed at one of the marker points along an ILS approach. A pilot with an ADF receiver can home in on it to find and follow the approach path.
Context Anchor
Seen on instrument charts and chart legends, especially around instrument approach routes and older navigation aid symbols.
Derivation
"Compass" here refers to the older sense of a radio compass (the ADF), which points toward a non-directional radio beacon. "Locator" means it helps the pilot locate a specific point on the approach. So the name literally describes its job: a beacon that the radio compass uses to locate the marker.
Why Pilots Care
Gives pilots a reliable initial fix and course guidance when flying an instrument approach in low visibility.
Intuition Check
Do not read compass locator beacon as the aircraft’s magnetic compass or as a visible light. Here, it means a ground-based radio signal used to locate a known point.
Example Sentence 1
The approach chart showed a compass locator beacon co-located with the outer marker, so the pilot tuned the ADF to use it as a backup to the localizer.
Example Sentence 2
On the approach plate the compass locator beacon marked the initial approach fix for the ILS.