Which statement correctly describes common fuel pump types in aircraft and their purposes?

Which statement correctly describes common fuel pump types in aircraft and their purposes?

• A. Hydraulic pumps provide primary feed; electric pumps provide only priming.
• B. Manual hand pumps supply main feed.
• C. Mechanical gear-driven pumps provide primary feed; electronic/auxiliary pumps provide boost or redundancy.
• D. Vacuum pumps supply fuel to injectors.

Answer: (C)

In most aircraft fuel systems, the main source of fuel pressure is the engine-driven mechanical pump, which is driven by the engine’s accessory gear train and provides the primary feed as long as the engine is running. Electric pumps, or electronic/auxiliary pumps, are added to supply boost or redundancy: they kick in to boost pressure when the engine-driven pump can’t keep up (such as at high power settings or high altitude), or serve as a backup if the primary pump fails. They can also be used for priming during start, but their main roles are boosting pressure and providing a reliable secondary path for fuel flow, enhancing safety and system reliability. The other statements confuse the roles (manual pumps are typically for priming, and vacuum pumps are for instrument vacuum, not fuel), which is why the described arrangement is the best fit.

In most aircraft fuel systems, the main source of fuel pressure is the engine-driven mechanical pump, which is driven by the engine’s accessory gear train and provides the primary feed as long as the engine is running. Electric pumps, or electronic/auxiliary pumps, are added to supply boost or redundancy: they kick in to boost pressure when the engine-driven pump can’t keep up (such as at high power settings or high altitude), or serve as a backup if the primary pump fails. They can also be used for priming during start, but their main roles are boosting pressure and providing a reliable secondary path for fuel flow, enhancing safety and system reliability. The other statements confuse the roles (manual pumps are typically for priming, and vacuum pumps are for instrument vacuum, not fuel), which is why the described arrangement is the best fit.