Definition
An electrically driven heading reference system that senses the horizontal component of the Earth's magnetic field using a fixed, pendulously mounted sensor (the flux valve) located in a wingtip or vertical stabilizer where magnetic disturbance is minimized. The sensor detects the direction of magnetic flux passing through its segmented core and transmits this information electrically to a remote indicator in the cockpit, providing a stable magnetic heading that is largely free from the dip errors and oscillation that affect a traditional liquid-filled magnetic compass.
Plain English
It is a magnetic compass that does not sit on the dashboard. A small sensor is mounted out in the wingtip or tail, where the aircraft's own electrical and metal interference is lowest. That sensor picks up the Earth's magnetic field and sends the heading to a display in front of the pilot, giving a steadier and more accurate reading than the bobbing compass on the windscreen.
Context Anchor
Seen in instrument flying discussions about heading information, compass systems, and electrically displayed direction in the cockpit.
Derivation
Flux refers to the flow of the Earth's magnetic field through the sensor's core. Gate comes from electrical engineering, where a gate is something that opens and closes to let a signal through; the sensor's core is electrically saturated and unsaturated in a repeating cycle, gating the magnetic flux on and off so it can be measured. Together, flux gate describes how the device works: it gates magnetic flux to detect direction.
Why Pilots Care
Delivers stable heading data during turns and acceleration when a traditional wet compass would swing or lag.
Analogy
It is like putting the compass sensor in a better spot and sending its reading to a display on the panel, instead of trying to read a small compass mounted where interference may be worse.
Intuition Check
Do not picture a physical gate opening and closing. In this term, the flux gate is an electrical magnetic-field sensor that helps the aircraft determine direction.
Example Sentence 1
During the preflight check, the pilot confirmed the heading indicator was slaved to the flux gate compass system and showed the correct magnetic heading.
Example Sentence 2
In the clouds the flux gate compass system kept supplying accurate direction while the airplane banked.