Which statement is true regarding bearings used in high-powered reciprocating aircraft engines?

The assertion that there is less rolling friction when ball bearings are used than when roller bearings are employed is accurate because of the fundamental differences in their designs. Ball bearings typically have a smaller contact area with the inner and outer races, which reduces the amount of surface area in contact and allows for smoother rotation. This results in lower rolling resistance compared to roller bearings, which have a larger contact area and generally more friction due to their shape and how they distribute loads.

In high-powered reciprocating engines, minimizing friction is critical for performance and efficiency, especially under high loads and varying operational conditions. Hence, the choice of using ball bearings often reflects a preference for reduced friction and improved efficiency in certain applications, enhancing overall engine performance.

Other choices suggest inaccuracies regarding bearing types and their operational characteristics which could lead to misunderstandings about the engineering principles behind the design choices in high-powered aircraft engines. For example, while the outer race of self-aligning ball bearings is designed for certain geometrical considerations, it doesn't hold true that it always equals the radius of the balls. Crankshaft bearings generally need to handle extreme loads, where roller bearings are more commonly used because they can better distribute these loads, contrary to the idea that ball bearings are the superior choice for such applications.