AMP - Aviation Maintenance Technician Powerplant Practice Exam

In order to maintain a constant oil pressure as the clearances between the moving parts of an engine increase through normal wear, the supply pump output?

1. Increases as the resistance offered to the flow of oil increases

2. Remains relatively constant (at a given rpm) with less oil being returned to the pump inlet by the relief valve

3. Remains relatively constant (at a given rpm) with more oil being returned to the pump inlet by the relief valve

4. Decreases as the engine temperature increases

The correct answer is: Remains relatively constant (at a given rpm) with less oil being returned to the pump inlet by the relief valve

As an engine runs, parts inside of it are inevitably subjected to wear and tear. This can cause clearances between the moving parts to increase, which leads to changes in oil flow and pressure. In order to maintain a constant oil pressure, the supply pump output needs to adjust accordingly. Option A is incorrect because as resistance to the flow of oil increases, the pump would have to work harder to maintain pressure, resulting in a decrease in output. Option C is incorrect because if more oil is being returned to the pump inlet, there would be less oil available to be pumped out and thus pressure would decrease. Option D is incorrect because engine temperature does not directly impact oil flow or pressure. Therefore, option B is the correct answer as it correctly states that the pump output remains relatively constant even as clearances between moving parts increase, allowing for consistent oil pressure.