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Oil return in a dry-sump system

Aviation Mechanic Powerplant (AMP) practice question 8 of 9 on Engine Lubrication Systems. ACS element AM.III.G.K4 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONIn a pressure dry-sump lubrication system, what returns oil to the tank as quickly as it accumulates in the engine sumps?

  1. AThe engine-driven pressure pump
  2. BGravity flow through the vent line
  3. CThe scavenger pumps
Show the answer and explanation

Correct answer: C. The scavenger pumps

  • A — incorrect The pressure pump supplies oil from the tank to the engine; returning the accumulated oil is the job of the scavenge side.
  • B — incorrect The tank vent equalizes pressure and does not carry return oil; the return flow is pumped, not gravity fed.
  • C — correct A pressure pump circulates oil through the engine, and scavenger pumps then return it to the tank as quickly as it accumulates in the engine sumps.

BACKGROUND

In a dry-sump system the oil supply is carried in a separate tank rather than in the engine. A pressure pump circulates oil through the engine, and scavenger pumps return it to the tank as quickly as it accumulates in the engine sumps. Because the scavenge side must handle oil that is foamy and mixed with air, scavenge capacity is greater than pressure capacity. The principal units in a typical reciprocating engine dry-sump oil system include an oil supply tank, an engine-driven pressure oil pump, a scavenge pump, an oil cooler with an oil cooler control valve, an oil tank vent, the necessary tubing, and pressure and temperature indicators. On multiengine aircraft, each engine is supplied with oil from its own complete and independent system.

STUDY TIP

Learn the component list for a dry-sump system, since the dry-sump system contains all the components of a wet-sump system plus the tank, external tubing, and scavenge pump. Keep the pressure side and scavenge side straight when tracing oil flow.

KEY POINTS

  • A dry-sump system carries its oil supply in a separate tank.
  • A pressure pump feeds the engine; scavenger pumps return oil to the tank.
  • Typical components include the tank, pressure pump, scavenge pump, oil cooler with control valve, tank vent, tubing, and indicators.

SOURCES

  • sources/amp-powerplant/ch06.txt "Dry Sump Oil Systems"
  • sources/amp-powerplant/ch06.txt "Reciprocating Engine Lubrication Systems"
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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.