Definition
Pumps in a dry-sump engine oil system that draw used oil out of the engine sumps and return it to the external oil tank for cooling and reuse.
Plain English
Pumps that pull oil that has already done its job lubricating the engine out of the bottom of the engine and send it back to the tank so it can be cooled and used again.
Context Anchor
Seen in aircraft engine oil system descriptions, especially when comparing oil systems that carry oil in a separate tank instead of storing it all inside the engine.
Derivation
From the Old French escouve, 'to sweep or clean out.' A scavenge pump 'sweeps out' the oil that has collected in the engine after lubricating the moving parts.
Why Pilots Care
Without working scavenge pumps, oil would pool inside the engine, starve the pressure pump, overheat, and risk engine damage.
Intuition Check
Scavenge does not mean the pump cleans the oil like a filter. Here it means the pump collects oil from the engine and sends it back to the oil tank.
Example Sentence 1
In a dry-sump engine, scavenge pumps return oil from the engine back to the tank after it has lubricated the moving parts.
Example Sentence 2
During the preflight, the pilot checked that both scavenge pumps were operating by noting normal oil quantity and temperature after engine start.