Aircraft systems and instrumentsQuestion 646 of 934

What is the purpose of the auxiliary (boost) fuel pump?

  1. To feed the engine at start and if the main pump fails
  2. To drain water from the sump during preflight
  3. To balance the fuel between the left and right tanks
  4. To raise fuel pressure for engine cooling in a climb
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Correct answer: To feed the engine at start and if the main pump fails

The electrically-driven auxiliary pump adds reliability to the fuel system.

Source: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 7: Aircraft Systems — Fuel Systems — Fuel-Pump System, page 185

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Questions last reviewed: 18 October 2026