Definition
In a flux gate compass system, the pickup coils are the three coils wound around the legs of a triangular, spider-shaped flux gate sensor. As the Earth's magnetic field passes through the sensor, it induces small electrical voltages in these coils. The strength of the voltage in each coil depends on how that coil is oriented relative to the Earth's magnetic field, and the combined signal from all three coils tells the system the aircraft's magnetic heading.
Plain English
Small wire coils inside the flux gate sensor that catch tiny electrical signals produced by the Earth's magnetic field. Those signals are then used to figure out which way the aircraft is pointing.
Context Anchor
Seen in diagrams and descriptions of the flux gate compass system, especially inside the remote compass sensor or flux valve.
Derivation
"Pickup" comes from the idea of picking up or receiving a signal, the same way a microphone or guitar pickup captures a small electrical signal. "Coil" refers to wire wound in loops, which is the shape needed to convert a changing magnetic field into a voltage. Together: coils that pick up a magnetic signal.
Why Pilots Care
They supply the magnetic reference data that keeps the compass accurate during turns and maneuvers when a standard magnetic compass would swing or lag.
Analogy
Think of the pickup coils like the pickups on an electric guitar. The guitar pickups don't make the sound themselves -- they sense the vibration of the strings and turn it into an electrical signal. The flux gate pickup coils don't generate the magnetic field; they just sense it and turn it into a signal the system can read.
Intuition Check
Pickup coils do not “pick up” physical parts or objects. Here, “pickup” means they detect a magnetic field and produce an electrical signal from it.
Example Sentence 1
The flight instructor explained that the three pickup coils in the flux gate sense the Earth's magnetic field and send heading information to the HSI.
Example Sentence 2
During preflight, the technician verified the alignment of the pickup coils to prevent heading errors in the compass system.