FAA Powerplant Written Practice Test

What issue does the relief valve in the venting system of a turbine engine oil tank help prevent?

1. Oil contamination

2. Oil pump cavitation by maintaining positive pressure

3. Cooling of the oil

4. Excessive oil pressure

The correct answer is: Oil pump cavitation by maintaining positive pressure

The relief valve in the venting system of a turbine engine oil tank is crucial for maintaining the proper operating conditions of the oil system. Specifically, its primary function is to prevent oil pump cavitation by ensuring that there is a consistent positive pressure within the oil tank and lines. Cavitation occurs when the pressure of the oil drops below its vapor pressure, leading to the formation of vapor cavities or bubbles. When these bubbles collapse, they can cause significant damage to the pump and result in inefficient oil delivery to the engine components. By allowing excess pressure to be released, the relief valve helps prevent situations where the oil pressure might drop too low, thus promoting stable and reliable operation of the oil pump. The other options do not accurately describe the primary function of the relief valve. While oil contamination and cooling are important considerations in engine operation, they do not pertain directly to the relief valve's role in maintaining pressure. Additionally, while excessive oil pressure management is important, it is the prevention of cavitation that is the specific issue addressed by the relief valve.