Definition
A magnetic field-sensing device used as the detecting element in a remote-indicating compass system. The flux gate is mounted in a wingtip or other location away from magnetic interference and senses the direction of the Earth's magnetic field by detecting how that field affects the magnetic flux flowing through a set of soft-iron cores wound with electrical coils. The signal it produces is sent electrically to a heading indicator in the cockpit.
Plain English
A small sensor mounted out in the wing that picks up the direction of the Earth's magnetic field and sends that information electrically to a heading display in the cockpit. It replaces the old idea of having the compass itself sit in front of the pilot.
Context Anchor
Seen in remote compass systems, heading displays, and troubleshooting when cockpit heading information appears wrong or unstable.
Derivation
The name comes from the way the device works: the Earth's magnetic flux (its field lines) is repeatedly 'gated' on and off through small iron cores by an alternating current in the coils. Each time the gate opens, the Earth's field induces a small voltage whose strength reveals the field's direction. 'Flux' means the magnetic field flowing through; 'gate' refers to the cyclic switching that allows the measurement to be made.
Why Pilots Care
It supplies stable, low-error magnetic heading data to navigation systems and autopilots without the turning and acceleration errors of wet compasses.
Intuition Check
Do not picture a physical gate that opens and closes. A flux gate is a magnetic sensor that measures the Earth’s magnetic direction.
Example Sentence 1
Before the first flight of the day, the pilot checked that the heading indicator was tracking correctly with the flux gate signal from the wingtip.
Example Sentence 2
During preflight the technician verified that the flux gate output matched the known runway heading.