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

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

• A. A lubrication system in which the oil cooler is in the pressure subsystem and the scavenged oil is not cooled before it is returned to the tank.
• B. A lubrication system in which the oil cooler is in the scavenge subsystem and the scavenged oil is cooled before it is returned to the tank.
• C. A lubrication system in which the oil cooler is external to the engine and the scavenged oil is cooled after it returns to the tank.
• D. A lubrication system with no oil cooler.

Answer: (B)

Hot-tank lubrication is defined by placing the oil cooler in the scavenge path, so the oil that returns from the bearings to the tank is cooled before it goes back into the oil sump. This arrangement cools the scavenged oil rather than the pressure-fed oil, keeping the return oil from heating the tank oil as it cycles back. That description matches the option where the cooler is in the scavenge subsystem and the scavenged oil is cooled before returning to the tank. If the cooler were in the pressure path, external to the engine, or if there were no cooler at all, those setups would not fit the hot-tank configuration.

Hot-tank lubrication is defined by placing the oil cooler in the scavenge path, so the oil that returns from the bearings to the tank is cooled before it goes back into the oil sump. This arrangement cools the scavenged oil rather than the pressure-fed oil, keeping the return oil from heating the tank oil as it cycles back. That description matches the option where the cooler is in the scavenge subsystem and the scavenged oil is cooled before returning to the tank. If the cooler were in the pressure path, external to the engine, or if there were no cooler at all, those setups would not fit the hot-tank configuration.