A remote-indicating fuel quantity system uses a transmitter (rotor) that rotates in proportion to fuel level, electromagnetically coupled to a receiver unit in the cockpit that duplicates the rotor's angular position without a mechanical connection. What type of device provides this remote position-indicating function?
- AA rheostat-based potentiometer circuit
- BA synchro (autosyn) system
- CA capacitance-type bridge circuit
- DA Bourdon tube mechanism
Show answer & explanationAnswer & explanation
Correct answer: B. A synchro (autosyn) system
A synchro (autosyn) system uses a transmitter and receiver, each with a rotor and stator winding, electromagnetically coupled so that the receiver rotor duplicates the angular position of the transmitter rotor without any mechanical linkage. This principle is used in many remote-indicating instruments, including fuel quantity, flap position, and control surface position indicators.
Why the other options are wrong
- A. A potentiometer changes resistance with position but does not electromagnetically duplicate angular position remotely in this manner.
- C. Capacitance-type systems are typically used for fuel quantity measurement based on dielectric changes, not angular position transmission.
- D. A Bourdon tube is a mechanical pressure-sensing device, unrelated to remote position transmission.
Synchro (Autosyn) System
An electromagnetic device consisting of a transmitter and receiver, each with rotor and stator windings, used to transmit angular position information remotely without mechanical linkage.
- Used in fuel quantity, flap position, and control surface indicators
- Transmitter rotor position induces corresponding voltages in receiver stator
- Receiver rotor aligns to match transmitter rotor angle
- No mechanical connection required between transmitter and indicator
Memory trick: Think of two dancers mirroring each other's moves across a room without touching — that's the synchro's electromagnetic mirroring.