FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsEasy
A mechanic is briefing an apprentice on the purpose of the electric fuel boost pump located inside a fuel tank. What is the primary function of this pump?
- ATo provide positive fuel pressure to the engine-driven pump and prevent vapor lock
- BTo pressurize the fuel tank vent system
- CTo meter fuel flow to the engine cylinders
- DTo transfer fuel between wing tanks during cruise
Show answer & explanationAnswer & explanation
Correct answer: A. To provide positive fuel pressure to the engine-driven pump and prevent vapor lock
The boost pump supplies fuel under positive pressure to the inlet of the engine-driven fuel pump, preventing vapor lock and fuel starvation at altitude, during hot conditions, or during engine start.
Why the other options are wrong
- B. The vent system is unpressurized and independent of the boost pump.
- C. Metering fuel to cylinders is done by the carburetor or fuel injection system, not the boost pump.
- D. Fuel transfer between tanks is handled by transfer pumps or crossfeed valves, a separate function.
Fuel Boost Pump
An electrically driven pump in the fuel tank that supplies fuel under positive pressure to the engine-driven pump inlet, preventing vapor lock.
- Prevents vapor lock at altitude/heat
- Used for engine starting and backup
- Independent of engine-driven pump
Memory trick: Boost pump BOOSTS pressure before the engine pump