Definition
A small instrument indicator, usually centered on zero with deflection markings on either side, that shows whether the remote indicating compass system is correctly aligned with the magnetic heading sensed by the flux valve. When the needle is centered, the heading indicator and the flux valve are in agreement; deflection to one side shows the system is in the process of slaving (re-aligning) the heading indicator to match the flux valve.
Plain English
A tiny gauge that tells the pilot whether the heading indicator is matched up with the airplane's magnetic sensor. Centered means matched. Off-center means the system is busy correcting itself.
Context Anchor
Seen in discussions and diagrams of remote indicating compass systems, especially systems that automatically keep a heading indicator matched to a remote magnetic sensor.
Derivation
From 'slave,' used in engineering to mean a device that automatically follows the movements of a master device. The flux valve is the master (it senses the true magnetic heading); the heading indicator is the slave (it follows). The meter shows how well the slave is keeping up.
Why Pilots Care
Lets the pilot verify the system is aligning correctly and spot malfunctions that could produce inaccurate heading information.
Intuition Check
Do not read “slaving” as an everyday social word here. In this instrument context, it means one part of the compass system is automatically following and matching another part.
Example Sentence 1
During the runup, the pilot glanced at the slaving meter and saw the needle oscillating gently around center, confirming the heading indicator was tracking properly.
Example Sentence 2
A steady needle on the slaving meter during cruise told the pilot the gyro was staying properly corrected.