What happens when a pilot operates the manifold pressure lever on an aircraft equipped with a constant speed propeller?

When a pilot operates the manifold pressure lever, they are adjusting the power output of the engine by controlling the amount of fuel-air mixture entering the engine cylinders. In an aircraft equipped with a constant-speed propeller, the propeller's speed (RPM) remains constant regardless of changes in engine power settings.

When the pilot increases the throttle, it implies an increase in engine power. To maintain the designated RPM despite the increased power, the propeller governor responds by increasing the pitch of the propeller blades. This adjustment effectively slows down the propeller's rotational speed to counterbalance the additional power being produced by the engine. Maintaining a constant RPM is crucial for optimal engine performance and efficiency, as well as ensuring smooth flight operations.

This describes why increasing the throttle results in an increase in propeller pitch to maintain constant RPM, making it the correct response to the question.