Definition
A fluxgate is a small, fixed magnetic sensor mounted in a stable part of the airframe (typically a wingtip or tail) that detects the direction of the Earth's magnetic field and sends that heading information electrically to the aircraft's heading indicator or HSI. It uses a ring-shaped iron core wrapped with coils; an alternating current drives the core in and out of magnetic saturation, and the surrounding Earth's magnetic field induces a measurable signal in the pickup coils that varies with the sensor's orientation relative to magnetic north.
Plain English
A fluxgate is a magnetic compass with no moving parts, mounted away from cockpit electrical noise, that senses which way is magnetic north and feeds that heading to your cockpit display electrically.
Context Anchor
Seen in HSI and remote compass system descriptions, especially where the instrument uses a magnetic sensor mounted away from cockpit interference.
Derivation
From 'flux' (the flow of magnetic field lines) and 'gate' (a device that opens and closes a path). The core is electrically driven into and out of magnetic saturation -- effectively 'gating' the magnetic flux on and off -- which is how the sensor extracts the Earth's field direction.
Why Pilots Care
Supplies accurate, low-drift heading information to the HSI without the turning and acceleration errors of a wet compass.
Analogy
Think of it as the sensing part of a compass, placed where the airplane’s metal and electrical equipment are less likely to disturb it. Instead of moving a visible needle, it sends an electrical signal to the cockpit display.
Intuition Check
A fluxgate is not a physical gate or valve. It is a magnetic sensor used to help determine aircraft heading.
Example Sentence 1
The HSI gets its heading reference from a fluxgate mounted in the wingtip, well away from the engine and cockpit electronics.
Example Sentence 2
During preflight the pilot verifies that the HSI heading matches the runway heading before trusting the fluxgate output.