Definition
A turbine engine lubrication system in which the oil cooler is positioned in the return (scavenge) line, so the oil is cooled before it is returned to the supply tank. The tank therefore holds oil that has already been through the cooler, keeping the tank temperature lower than in a hot-tank system.
Plain English
A way of arranging an engine's oil system so the oil is cooled first and then sent back to the storage tank. Because the oil is cooled before it reaches the tank, the tank stays cooler.
Context Anchor
Seen in aircraft engine maintenance descriptions, especially when tracing how oil moves from the engine, through the cooler, and back to the tank.
Derivation
Called 'cold-tank' because the oil reaches the tank after passing through the cooler, so the tank itself stays at a lower temperature. The contrast is the 'hot-tank' system, where the cooler sits in the supply line and oil enters the tank still hot from the engine.
Why Pilots Care
Prevents oil overheating and maintains consistent lubrication pressure and flow in high-performance or inverted-flight capable engines.
Grounding Statement
After the oil leaves the hot engine, it passes through a cooler before sitting in the tank.
Intuition Check
Do not read “cold” as freezing or chilled. In this term, “cold” means cooler than oil that has just left the engine, because the oil is cooled before it reaches the tank.
Example Sentence 1
In a cold-tank lubrication system, the oil cooler is placed in the scavenge line so returning oil is cooled before it enters the supply tank.
Example Sentence 2
Mechanics check the external tank level in cold-tank systems before each flight to ensure adequate oil supply.