FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsMedium
A twin-engine aircraft experiences a fuel pump failure on the left engine. The pilot opens the fuel crossfeed valve. What is the primary function this action performs?
- AIt vents excess fuel overboard to reduce weight
- BIt shuts off fuel supply to both engines simultaneously for safety
- CIt allows fuel from the right tank to supply the left engine, or vice versa
- DIt transfers fuel between tanks to correct a lateral imbalance without engine use
Show answer & explanationAnswer & explanation
Correct answer: C. It allows fuel from the right tank to supply the left engine, or vice versa
A crossfeed valve connects the fuel systems of both engines so that fuel from one tank can supply either engine, allowing the aircraft to continue using fuel from the tank on the side with the inoperative pump or engine.
Why the other options are wrong
- A. Fuel jettison, not crossfeed, vents fuel overboard.
- B. Crossfeed does not shut off fuel to both engines; it reroutes fuel supply.
- D. That describes a fuel transfer system, a separate function from crossfeed.
Fuel Crossfeed System
A system with a valve that connects fuel lines between engines so fuel from either tank can supply either engine, commonly used during single-engine or pump-failure operations.
- Distinct from fuel transfer systems used to balance tank quantities
- Typically manually selected by the pilot
- Critical for extending range or managing failures in multi-engine aircraft
Memory trick: Crossfeed lets one tank feed either engine like a shared straw.