How is 'slip' defined within propeller dynamics?

In propeller dynamics, 'slip' is defined as the difference between the geometric pitch and the effective pitch of the propeller.

Geometric pitch refers to the angle of the blades as designed, which determines how far the propeller would move forward in a single rotation if there were no slippage – essentially the theoretical distance traveled. Effective pitch, on the other hand, describes the actual distance the propeller moves through the air during operation, which can be less due to factors such as air resistance and drag.

When a propeller is in operation, various forces act on it, which can prevent it from achieving its designed geometric pitch. The result is that the effective pitch often falls short of the geometric pitch, and this discrepancy is what is referred to as 'slip.' This concept is crucial in understanding propeller efficiency and performance, as a high degree of slip indicates poor performance and energy conversion.