Definition
A heading indicator whose gyroscope is automatically corrected by a remote magnetic sensor (typically a flux gate or flux valve mounted in a wingtip or tail), so the displayed heading stays aligned with magnetic north without the pilot manually resetting it.
Plain English
A heading instrument that uses a spinning gyro for steady, smooth indication, but quietly keeps itself synced to magnetic north using a magnetic sensor somewhere on the aircraft. The pilot doesn't have to keep correcting it.
Context Anchor
Seen during the after-engine-start instrument check, when the pilot verifies that the heading system is aligned and operating normally before taxi.
Derivation
Slaved' here is an engineering term meaning one device is automatically controlled or aligned by another. The gyrocompass is 'slaved' to the magnetic sensor because the sensor tells it where magnetic north is and the gyro follows.
Why Pilots Care
Prevents heading drift and removes the need for frequent manual resets, giving reliable directional information in instrument flight.
Intuition Check
“Slaved” does not mean the pilot simply set the instrument once by hand. Here it means the heading display is automatically made to follow a magnetic reference.
Example Sentence 1
After engine start, the pilot checked that the slaved gyrocompass agreed with the magnetic compass before taxi.
Example Sentence 2
In the turn the slaved gyrocompass held steady while an unslaved directional gyro would have begun to precess.