What happens if both the electric boost pump and the engine-driven low-pressure pump fail?

• A. The engine will stall
• B. The engine will flame out
• C. The engine will overheat
• D. The engine will shut down

Answer: (B)

In the event that both the electric boost pump and the engine-driven low-pressure pump fail, the most critical consequence is that the engine will flame out. The electric boost pump is responsible for providing additional fuel pressure to the engine, while the engine-driven low-pressure pump supplies fuel from the tank to the engine itself. If both systems are inoperative, there will be insufficient fuel pressure to keep the engine running, leading to a flameout due to a lack of fuel.

A flameout typically occurs when the engine is unable to maintain combustion because the required fuel flow is interrupted. This situation highlights the importance of redundancy in fuel systems; the design intends for multiple pumps to ensure continued operation even if one fails.

The other outcomes are less likely: the engine stalling typically refers to a temporary interruption in power, which isn’t as severe as a flameout. Overheating might occur due to other factors but is not a direct result of the pumps failing. An engine shutdown generally indicates a controlled process where the pilot turns off the engine, which differs from an uncontrolled flameout due to fuel starvation. Therefore, faced with the failure of both pumps, the critical issue is indeed the loss of fuel and subsequent flameout.