What are the two types of propeller slips?

• A. Geometric pitch—Theoretical and Effective pitch—Actual
• B. Geometric pitch—Actual and Effective pitch—Theoretical
• C. Geometric pitch—Theoretical
• D. Effective pitch—Actual

Answer: (A)

The idea being tested is how propeller pitch is described and what slip means in that context. The propeller has two ways to define pitch: geometric (or theoretical) pitch, which is the distance the blade would move in one revolution if there were no aerodynamic losses—it's based on the blade’s geometry. The other is effective (or actual) pitch, which is the distance the aircraft actually moves forward in one revolution under real flight conditions, with air resistance and loading.

Propeller slip is the difference between those two values. So the two terms involved are geometric pitch (theoretical) and effective pitch (actual). The other choices mix or omit these pairings, which doesn’t align with how slip is defined in propeller theory.