Plain English Meaning

The pan at the bottom of the engine that stores the oil. Oil flows down into it after lubricating the engine, then gets picked back up and sent around again.

Full Definition

The reservoir at the bottom of an aircraft engine that holds the engine's oil supply. Oil drains into the sump after circulating through the engine, where it is cooled and held until the oil pump pulls it back through the system.

Context Anchor

Seen in aircraft engine oil-system descriptions and during oil level, leak, and engine-condition checks.

Derivation

Sump' comes from a Middle Dutch and Low German word meaning 'swamp' or 'pool of liquid.' The sense carried into engineering as 'a low place where liquid collects' — exactly what an oil sump does at the bottom of the engine.

Why Pilots Care

Knowing whether an engine uses a wet sump affects how oil quantity is checked, how much oil is carried, and certain operating limitations.