FAA Powerplant Written Practice Test

Which component of a piston engine is most susceptible to the defect known as "pitting"?

1. Piston crowns

2. Connecting rods

3. Bearing races

4. Cam lobes

The correct answer is: Bearing races

The component of a piston engine that is most susceptible to the defect known as "pitting" is the bearing races. Pitting is a form of surface fatigue failure characterized by the formation of small holes or pits on the surface of a metal. This typically occurs due to repeated stress cycles and can significantly weaken the material. Bearing races, which are part of the engine's bearings, experience constant and direct contact with rotating components, exposing them to high loads and friction. Over time, the repetitive stress from the moving parts can lead to surface fatigue, which manifests as pitting. Since these surfaces are designed to handle heavy loads and provide smooth rotation for various engine components, they are particularly vulnerable to such damage. While other components like pistons, connecting rods, and cam lobes can experience wear and damage, they do not typically develop pitting to the same extent as bearing races do. Piston crowns, for instance, may suffer from thermal degradation or deposits, and connecting rods can experience bending or fatigue, but these issues are different from the specific surface degradation characterized by pitting.