FAA Aviation Mechanic Airframe (AMA)Airframe Electrical and InstrumentsHard
An aircraft uses a remote-indicating compass system in which a transmitter unit senses magnetic heading and electrically transmits that data to a cockpit indicator without a direct mechanical linkage. What type of device performs this heading transmission function?
- AVertical speed indicator diaphragm
- BFlux valve (magnetic flux detector)
- CStatic air temperature probe
- DPitot heat control relay
Show answer & explanationAnswer & explanation
Correct answer: B. Flux valve (magnetic flux detector)
A flux valve, also called a magnetic flux detector, senses the direction of the earth's magnetic field and generates an electrical signal proportional to heading, which is transmitted via a synchro system to remote heading indicators such as an RMI or HSI, eliminating direct mechanical linkage. The other listed components are unrelated instrument or system devices that do not perform heading sensing.
Why the other options are wrong
- A. The VSI diaphragm senses static pressure change rate, unrelated to heading.
- C. A static air temperature probe measures outside air temperature, not heading.
- D. A pitot heat relay controls heating elements to prevent pitot icing, unrelated to heading sensing.
Flux Valve (Flux Gate)
A magnetic heading sensor, usually mounted in a wingtip or tail away from magnetic interference, that electrically transmits heading information to remote cockpit indicators via a synchro system.
- Mounted away from magnetic interference sources
- Sends signal through a synchro/autosyn transmission system
- Feeds remote indicators such as RMI, HSI, and autopilot heading systems
Memory trick: Flux valve is the wingtip 'compass spy' radioing heading data to the cockpit