If the oil line between the scavenger pump and the oil cooler bursts, what will happen to the return oil?

When the oil line between the scavenger pump and the oil cooler bursts, the return oil will typically be vented to the atmosphere instead of being directed back to the oil tank or remaining within the engine system. In this situation, the scavenger pump, which is responsible for returning oil from the engine to the oil system, will continue to operate, but due to the burst line, the oil instead flows out of the system, which could lead to it being pumped overboard.

The burst in the line creates a pressure drop, allowing the oil to escape rather than returning to the tank where it should normally be contained and cooled. This loss of oil may result in other operational issues, such as reduced lubrication and potential damage to the engine if oil levels drop significantly. Therefore, the scenario described in the question accurately reflects that the oil would be undesirably lost to the environment rather than leaking into the engine itself, evaporating, or simply returning to the tank.