What is the reason for using cam-ground pistons in certain aircraft engines?

Using cam-ground pistons in certain aircraft engines primarily serves to provide a better fit at operating temperatures. Cam-ground pistons are designed with an oval shape in their diameter, which allows them to expand and adjust their shape as the engine heats up during operation.

As the temperature rises, the piston expands, and the cam-ground design helps maintain a closer tolerance between the piston and the cylinder wall at high operating temperatures. This reduces wobble and improves the overall seal between the piston and the cylinder, which is crucial for maintaining efficient combustion and preventing blow-by of gases. By optimizing the fit in this manner, cam-ground pistons can enhance engine performance and durability, contributing to the overall efficiency and reliability of the engine.

This design also helps in maintaining a balance between a snug fit when the engine is cold and allowing necessary clearance when the engine is hot, ultimately leading to a more efficient combustion process and better engine performance.