Constant speed propeller

A type of propeller used on an airplane to hold the engine at a constant RPM as the air load on the propeller changes. A centrifugal governor senses the engine RPM, and if it increases above that for which the governor is set, the pitch of the propeller blades will increase. This increased blade angle increases the air load on the propeller, and the engine slows down. If the RPM drops below that for which the governor is set, the propeller pitch will decrease, and the decreased air load allows the engine to speed back up to its on-speed condition.