FAA Powerplant Written Practice Test

Mean bearing oil seals in turbine engines are typically what type?

1. Rubber and synthetic composites

2. Labyrinth and/or carbon rubbing

3. Metallic and polymer blends

4. Flexible and rigid combinations

The correct answer is: Labyrinth and/or carbon rubbing

Mean bearing oil seals in turbine engines are primarily designed to effectively control oil leakage and minimize the entry of contaminants. The use of labyrinth seals and/or carbon rubbing seals is prevalent in turbine engines due to their effectiveness in achieving a reliable seal while being able to withstand high temperatures and pressures. Labyrinth seals utilize a series of grooves or channels that create a tortuous path for the oil, making it difficult for oil to escape, while also allowing for a minimal amount of leakage that is manageable and does not affect engine performance. Carbon rubbing seals, on the other hand, provide a low-friction interface, which is critical in high-speed turbine applications. They can conform to the shaft and create a seal without significant wear on the rotor, which is essential for maintaining the integrity and efficiency of the engine. In summary, the selection of labyrinth and carbon rubbing seals for mean bearing oil seals is due to their ability to maintain a balance between sealing effectiveness, durability, and performance in the demanding environment of a turbine engine.