What defines a cold-tank lubrication system for a turbojet engine?

• A. A lubrication system in which the oil cooler is in the scavenge subsystem, and the scavenged oil is cooled before returned to the tank.
• B. A lubrication system in which the oil cooler is in the pressure subsystem and the scavenged oil is not cooled.
• C. A lubrication system with no oil cooler.
• D. A lubrication system where the oil reservoir is cooled by external air.

Answer: (C)

Cold-tank lubrication systems are defined by the absence of an oil cooler in the lubrication loop. The oil is drawn from the tank to feed the engine, and after use it returns to the same tank without passing through a cooler in the flow path. Temperature control relies on the tank’s ambient environment rather than an in-line cooling loop.

If a cooler were placed in the scavenge path, or in the pressure path, or if the reservoir itself were actively cooled by external means, the system would involve active cooling in the oil loop, which would not meet the “cold-tank” definition.