What happens to the blade angle in a Constant Speed Propeller when oil enters the piston?

In a Constant Speed Propeller system, oil pressure is used to control the pitch of the propeller blades. When oil enters the piston mechanism within the propeller hub, it applies pressure against a piston that changes the blade angle. Specifically, as oil enters the piston, it forces the blades to change to a higher angle, known as "coarse pitch."

This change allows the propeller to maintain optimal performance at higher airspeeds by reducing drag and increasing efficiency. By increasing the blade angle, the propeller can better match engine performance to varying flight conditions, particularly during climb and cruise phases. This mechanism is fundamental to the operation of constant-speed propellers, enabling pilots to manage power output effectively and maintain optimal RPMs for fuel efficiency and performance.

Thus, the correct understanding in this situation is that the blade angle increases when oil enters the piston, facilitating improved propulsion efficiency.