Definition
A turbine engine lubrication system in which oil returning from the engine bearings and gearboxes is routed back to the oil tank without first passing through a cooler. Cooling is performed downstream of the tank, between the tank and the engine, so the oil sitting in the tank remains hot.
Plain English
An engine oil system where the oil tank holds hot oil. The oil is cooled after it leaves the tank on its way back into the engine, not before it goes into the tank.
Context Anchor
Seen in aircraft powerplant lubrication-system discussions, especially when identifying where the oil cooler is located in the oil flow path.
Derivation
Called 'hot-tank' simply because the oil tank stores oil that is still hot from the engine. The contrast is the 'cold-tank' system, where oil is cooled before entering the tank, so the tank holds cool oil.
Why Pilots Care
Knowing whether an engine uses a hot-tank or cold-tank system helps a technician interpret oil temperature readings correctly and troubleshoot the oil cooler, since the cooler sits in a different place in each system.
Intuition Check
Hot-tank does not mean the tank has a heater. It means the oil reaches the tank before it passes through the cooler.
Example Sentence 1
Because this engine uses a hot-tank lubricating system, the oil cooler is located on the pressure side, between the tank and the engine.
Example Sentence 2
During preflight, the mechanic noted higher tank temperatures typical of the hot-tank lubricating system.