FAA Powerplant Written Practice Test

What is a primary characteristic of the hydraulic main bearing in turbine engines?

1. It requires constant monitoring of the oil temperature

2. It depends on gravity for its functionality

3. It helps reduce vibration tendencies in the rotor system

4. It allows for rapid rotor acceleration

The correct answer is: It helps reduce vibration tendencies in the rotor system

A primary characteristic of the hydraulic main bearing in turbine engines is its role in helping to reduce vibration tendencies in the rotor system. These bearings are designed to provide a stable environment for the rotating components, minimizing the impact of vibrations that can originate from various sources, such as aerodynamic forces or mechanical imbalances. By effectively dampening these vibrations, hydraulic main bearings contribute to smoother operation, enhanced reliability, and extended lifespan of engine components. The design of hydraulic bearings typically allows for a thin film of lubricating oil to support the rotor, which not only facilitates smooth rotation but also helps in absorbing and dissipating vibrational energy. This characteristic is critical in maintaining the overall performance and safety of turbine engines, especially at high operational speeds where the potential for vibration increases. While monitoring oil temperature and gravity effects are important in other contexts, they do not primarily define the primary purpose and characteristic of hydraulic main bearings. Rapid rotor acceleration, though beneficial, is a result of various factors and designs in the engine, rather than a defining characteristic of the bearing itself.