Which statement correctly describes a dry-sump lubrication system?

• A. Wet-sump stores oil in the engine sump and uses a pump to circulate.
• B. Dry-sump uses external reservoir and scavenger pumps.
• C. Reservoir stores oil permanently.
• D. Oil cooler routes oil back to tank.

Answer: (B)

In a dry-sump lubrication system the oil is stored in an external tank, not in the engine’s sump. Scavenger pumps continuously pull oil from the crankcase and push it into that external reservoir. The engine’s pressure pump then draws oil from the reservoir to lubricate the moving parts, with the oil circulating through a cooler before returning to the reservoir. This arrangement keeps the crankcase dry, prevents oil starvation during high-load or inverted flight, and allows a larger oil capacity and flexible placement of the cooler and pumps.

The other descriptions describe a wet-sump setup, where oil sits in the engine sump and is circulated by a pump, which is not how a dry-sump system operates. The idea of storing oil permanently in a reservoir isn’t accurate, since the oil is continually circulated between the engine and the external tank. The specific role of the cooler in a dry-sump arrangement is to cool the oil as it circulates, with the cooled oil returning to the reservoir or to the supply path, rather than implying a fixed return to a tank in isolation.