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.
Plain English
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.
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.
Intuition Check
Do not confuse an oil sump with a fuel sump or a drain point. Here, sump means the engine’s oil collection and storage area.
Example Sentence 1
During preflight, the pilot pulled the dipstick and confirmed the oil level in the sump was within limits.
Example Sentence 2
A wet-sump engine stores all its lubricating oil in the sump at the bottom of the crankcase.