FAA Powerplant Written Practice Test

What is the pumping capacity of the scavenger pump in a dry sump aircraft engine lubrication system?

1. Less than the capacity of the oil pressure pump

2. Equal to the capacity of the oil pressure pump

3. Greater than the capacity of the oil pressure pump

4. Varies based on engine size

The correct answer is: Greater than the capacity of the oil pressure pump

In a dry sump aircraft engine lubrication system, the scavenger pump is designed to handle the oil that has circulated through the engine and is returning to the oil reservoir. Its primary function is to efficiently remove oil collected in the sump area and return it to the tank for re-circulation. The scavenger pump typically has a greater capacity than the oil pressure pump because it must cope with the excess oil that accumulates during engine operation. The oil pressure pump is responsible for delivering oil under pressure to the engine’s bearings and other moving parts for lubrication. However, oil flow rates and the overall mechanism of oil circulation can create situations where more oil needs to be returned than is available through the pressure generated by the oil pressure pump. This ensures that all oil is effectively managed and prevents any oil starvation conditions. Therefore, the design of the scavenger pump ensures that it can handle the requirements of returning oil from the engine back to the oil tank reliably while maintaining proper lubrication throughout the engine.