FAA Powerplant Written Practice Test

What is a characteristic of a thrust bearing used in most radial engines?

1. Deep-grooved ball

2. Small diameter plain

3. Full roller bearing

4. Split sleeve type

The correct answer is: Deep-grooved ball

In radial engines, thrust bearings are designed to handle the axial loads generated during operation. A deep-grooved ball bearing is often used in these applications due to its ability to accommodate both radial and axial loads effectively. The deep grooves allow the balls to sit deeper within the races, providing a greater contact area and enhancing load distribution. This design contributes to increased stability and the ability to carry higher loads while maintaining a smooth operation. The other types of bearings mentioned may not provide the suitable characteristics needed for the thrust application in radial engines. For instance, a small diameter plain bearing might lack the necessary load capacity or could lead to increased wear under axial stress. Full roller bearings are typically used for radial loads but may not be ideal for certain thrust applications where axial stability is critical. The split sleeve type bearing could offer some advantage in terms of ease of maintenance but isn’t as effective in handling the dynamic loads present in a radial engine's thrust system compared to deep-grooved ball bearings. Thus, the characteristics of a deep-grooved ball bearing make it the best choice for ensuring reliable operation in the thrust bearing application of radial engines.