The propeller slip is defined as

The propeller slip is defined as

• A. The difference between geometric pitch and effective pitch
• B. The difference between thrust and drag
• C. The blade's angle of attack
• D. The rpm difference between engines

Answer: (A)

Propeller slip is the difference between the distance the prop would advance in one revolution if there were no slippage (geometric pitch) and the distance it actually advances in flight (effective pitch). Geometric pitch is set by the blade geometry, the theoretical advance per revolution, while effective pitch is the real advance achieved at a given airspeed and RPM. The gap between these two measures shows how much the blade is “slipping” through the air due to aerodynamic effects. The other ideas—thrust minus drag, blade angle of attack, or rpm differences between engines—do not describe this distance difference and thus are not slip.

Propeller slip is the difference between the distance the prop would advance in one revolution if there were no slippage (geometric pitch) and the distance it actually advances in flight (effective pitch). Geometric pitch is set by the blade geometry, the theoretical advance per revolution, while effective pitch is the real advance achieved at a given airspeed and RPM. The gap between these two measures shows how much the blade is “slipping” through the air due to aerodynamic effects. The other ideas—thrust minus drag, blade angle of attack, or rpm differences between engines—do not describe this distance difference and thus are not slip.