Definition
A built-in self-checking circuit within a VOR ground station that continuously verifies the accuracy and integrity of the transmitted signal. If the bearing accuracy drifts beyond approximately one degree, or if certain signal components fail, the monitor either removes the identification (Morse code ID) and navigation features from the signal or shuts the station down, alerting pilots that the VOR should not be used for navigation.
Plain English
A watchdog inside the VOR ground station that constantly checks whether the station is putting out a correct signal. If something goes wrong, it either removes the station's ID code or takes the station off the air so pilots know not to trust it.
Context Anchor
Seen in discussions of VOR ground station components and how the station protects the accuracy of the navigation signal pilots receive in the aircraft.
Derivation
Automatic' (from Greek 'automatos', acting of itself) and 'monitor' (from Latin 'monere', to warn). Together: a system that watches and warns without needing a human to check it.
Why Pilots Care
It prevents a faulty VOR signal from reaching aircraft, protecting navigation accuracy and reducing the risk of course deviation or missed approaches.
Intuition Check
Do not read automatic monitoring system as something in the airplane that checks the pilot’s instruments automatically. In this context, it is part of the VOR ground station and it checks that station’s own transmitted signal.
Example Sentence 1
When the Morse identifier on the VOR went silent, the pilot realized the automatic monitoring system had taken the station off the air and selected a different navaid.
Example Sentence 2
Because the automatic monitoring system had already shut down the primary transmitter, the standby unit came online before any aircraft received inaccurate bearings.