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Reciprocating engine oil pump type

Aviation Mechanic Powerplant (AMP) practice question 6 of 9 on Engine Lubrication Systems. ACS element AM.III.G.K2 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONAs oil enters a reciprocating engine, what type of pump pressurizes it?

  1. AA positive-displacement gear pump
  2. BA variable-displacement vane pump
  3. CA centrifugal pump driven by the crankshaft
Show the answer and explanation

Correct answer: A. A positive-displacement gear pump

  • A — correct Oil entering the engine is pressurized by a gear-type pump that is a positive displacement pump consisting of two meshed gears revolving inside a housing with small clearance between the teeth and the housing.
  • B — incorrect The engine oil pressure pump is a fixed, positive displacement design using meshed gears, not a vane pump whose displacement varies.
  • C — incorrect The engine oil pressure pump is a gear-type positive displacement pump whose splined drive shaft extends to an accessory drive shaft on the engine, not a centrifugal pump driven directly by the crankshaft.

BACKGROUND

The engine-driven oil pressure pump is a gear-type, positive displacement pump. Two meshed gears revolve inside a close-fitting housing; one gear is attached to a splined drive shaft that extends from the pump housing to an accessory drive shaft on the engine. As oil enters the gear chamber it is trapped between the gear teeth and the sides of the chamber, carried around the outside of the gears, and discharged from the pressure port into the oil screen passage. Seals prevent leakage around the drive shaft. Because output rises with engine speed, an oil pressure regulating valve, sometimes called a relief valve, limits oil pressure to a predetermined value that depends on the installation.

STUDY TIP

Remember that the pump moves a fixed volume for every revolution, which is why a regulating valve rather than the pump itself controls system pressure. Be able to trace the oil path from pump inlet, around the gears, to the discharge port and oil filter.

KEY POINTS

  • The engine oil pressure pump is a gear-type, positive displacement pump.
  • Oil is carried around the outside of the meshed gears and discharged into the oil screen passage.
  • An oil pressure regulating valve limits the pressure to a predetermined value for the installation.

SOURCES

  • sources/amp-powerplant/ch06.txt "Oil Pump"
  • sources/amp-powerplant/ch06.txt "Oil Pressure Regulating Valve"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-32B Aviation Maintenance Technician Handbook – Powerplant, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.