FAA Aviation Mechanic Powerplant (AMP)Fuel, Induction and LubricationEasy
A mechanic is briefing an owner-pilot on the fuel system of a light twin equipped with individual tanks in each wing. Which statement best describes the primary purpose of the fuel selector valve?
- AIt vents fuel tank vapors overboard to prevent excessive internal pressure
- BIt allows the pilot to choose which tank or combination of tanks supplies fuel to each engine
- CIt filters solid contaminants from the fuel before it reaches the engine-driven pump
- DIt regulates fuel pressure delivered to the carburetor or fuel injector
Show answer & explanationAnswer & explanation
Correct answer: B. It allows the pilot to choose which tank or combination of tanks supplies fuel to each engine
The fuel selector valve is a manually (or electrically) operated valve that lets the pilot direct fuel flow from a chosen tank, both tanks, or the off position to the engine(s). Filtering, pressure regulation, and venting are performed by other components.
Why the other options are wrong
- A. Venting is handled by the fuel tank vent system.
- C. Filtering contaminants is the job of the fuel strainer/filter, not the selector valve.
- D. Pressure regulation is done by a fuel pump relief valve or pressure regulator.
Fuel Selector Valve
A valve, usually pilot-operated, that directs fuel from a selected tank (or tanks) to the engine and provides an OFF position for shutdown or emergencies.
- Common positions: LEFT, RIGHT, BOTH, OFF
- Located between tanks and fuel pump/strainer
- Allows tank balancing and isolation of a leaking tank
Memory trick: Tank picks, valve flicks, strainer sticks (catches dirt), pump kicks fuel to the engine.