Definition
A turbine engine lubrication system in which oil returning from the engine bearings and accessories is routed directly back to the oil tank without first passing through a cooler. The oil cooler is located downstream of the tank, on the supply (pressure) side of the system, so the oil is cooled before being delivered back to the engine rather than before being returned to the tank.
Plain English
A type of engine oil system where the used oil goes back into the tank still hot, and is only cooled on its way out to the engine again. The tank itself runs warm, which is why it is called a hot-tank system.
Context Anchor
Seen in aircraft engine lubrication system descriptions, especially for turbine engines and dry-sump oil systems.
Derivation
Called 'hot tank' because the oil tank holds oil at the high temperature it had when it left the engine. The opposite arrangement is a 'cold-tank' system, where the oil is cooled before going back into the tank.
Why Pilots Care
Determines how quickly oil reaches operating temperature, affects warm-up procedures, and influences the risk of oil thinning or coking during prolonged ground operations.
Analogy
Think of returning hot soup to a pot before it passes through a cooling step. The pot itself stays hot because the liquid reaches it before being cooled.
Intuition Check
“Hot-tank” does not mean the system is overheating or unsafe. It means the oil tank normally receives oil while that oil is still hot from the engine.
Example Sentence 1
Most modern turbine engines use a hot-tank lubrication system, with the oil cooler placed on the pressure side between the tank and the engine.
Example Sentence 2
In the hot-tank setup the scavenge pumps return oil directly to the tank without passing through the cooler first.