Definition
A flux valve is a sensing device, typically mounted in a wingtip or tail where magnetic interference is minimal, that detects the horizontal component of the Earth's magnetic field and sends that directional information electrically to the heading system. It has no moving parts; instead, it uses a set of coils wound around a soft-iron core to measure how the Earth's magnetic field flows through the core, allowing the system to calculate the aircraft's magnetic heading.
Plain English
A small electronic sensor placed in a quiet part of the airframe that reads the direction of the Earth's magnetic field and feeds that information to the cockpit heading instruments.
Context Anchor
Seen in instrument flying when learning how an AHRS or other heading system gets magnetic heading information.
Derivation
The word comes from Latin fluxus, meaning 'a flowing.' In this device, magnetic lines of force 'flow' through the iron core, and the valve senses how that flow shifts as the aircraft turns. The 'valve' part refers to the way the core alternately allows and resists the magnetic flux as the coils energize, much like a valve opening and closing.
Why Pilots Care
Supplies reliable magnetic heading data essential for navigation when visual references are lost.
Intuition Check
Do not read “valve” as something that opens and closes to control fluid. A flux valve is a magnetic sensor, not a plumbing part.
Example Sentence 1
The flux valve in the left wingtip feeds magnetic heading data to the HSI.
Example Sentence 2
During preflight the pilot confirmed the flux valves were aligned before taxiing for an IFR departure.