FAA Aviation Mechanic Powerplant (AMP)Reciprocating EnginesMedium
A mechanic notes that a float-type carburetor is equipped with an accelerating pump. What is the primary purpose of this component?
- ATo maintain constant fuel pressure during high-altitude cruise
- BTo automatically enrich the mixture during full-power takeoff
- CTo provide a momentary charge of extra fuel when the throttle is opened rapidly
- DTo prevent fuel from siphoning out of the carburetor bowl during shutdown
Show answer & explanationAnswer & explanation
Correct answer: C. To provide a momentary charge of extra fuel when the throttle is opened rapidly
The accelerating pump injects a shot of extra fuel into the airstream when the throttle is opened quickly, compensating for the momentary lag in airflow response and preventing a lean mixture and engine hesitation or stumble.
Why the other options are wrong
- A. Fuel pressure regulation at altitude is handled by mixture control and altitude compensation, not the accelerating pump.
- B. Full-power enrichment for continuous high power is the function of the economizer/power enrichment valve.
- D. Preventing bowl siphoning is unrelated to the accelerating pump's function.
Accelerating Pump
A carburetor component that injects a temporary shot of fuel when the throttle is rapidly opened to prevent a lean mixture and engine hesitation.
- Activated by throttle linkage
- Prevents lean-out/hesitation on rapid throttle opening
- Distinct from the economizer/power enrichment valve
Memory trick: Accelerate = quick squirt to catch up with air.