Definition
A mechanism that automatically aligns the compass card of a Radio Magnetic Indicator (RMI) with magnetic north by linking it to a remote magnetic sensor (typically a flux detector or flux valve) mounted in a wingtip or other location away from magnetic interference. The slaving system continuously corrects the RMI's heading display so that it always reads the aircraft's actual magnetic heading, allowing the RMI's needles to point accurately to the bearing of NDB or VOR stations.
Plain English
It's the automatic system that keeps the RMI's compass dial lined up with magnetic north on its own, so the pilot doesn't have to manually adjust it during flight.
Context Anchor
Seen when using an RMI for navigation, especially when checking whether the instrument’s heading card and bearing pointers can be trusted.
Derivation
Slaving' here means one device is made to follow another automatically — the RMI compass card is 'slaved' to the remote magnetic sensor, so it copies whatever heading the sensor detects.
Why Pilots Care
A misaligned slaving system produces incorrect relative bearings that can lead to navigation errors or failed course intercepts.
Analogy
It is like a clock that automatically resets itself to the correct time, instead of slowly drifting and needing you to fix it by hand.
Intuition Check
Do not assume the slaving system is what points to the radio station. It keeps the RMI heading card aligned with magnetic heading; the bearing pointer is separate information shown on that card.
Example Sentence 1
During the runup, the pilot checked the RMI slaving system and confirmed the compass card matched the magnetic heading shown on the standby compass.
Example Sentence 2
After maintenance, the RMI slaving system was tested to confirm the compass card followed heading changes without lag.