What is the purpose of the propeller governor in a reciprocating engine?

The purpose of the propeller governor in a reciprocating engine is to maintain a constant propeller speed by adjusting the blade pitch. The governor achieves this by sensing the rotational speed of the propeller and automatically changing the angle of the blades. When the propeller speed exceeds a predetermined limit, the governor increases the pitch of the blades, which reduces the angle of attack and thus slows the propeller speed down. Conversely, if the speed drops below this limit, the governor decreases the pitch, allowing for a faster rotation.

This mechanism is crucial for optimizing engine performance and fuel efficiency while ensuring stable flight conditions. Maintaining an optimal propeller speed is important for effective thrust generation and overall efficiency of the aircraft during various phases of flight, such as climbing, cruising, or descending. The other options pertain to different functionalities that do not involve the direct control of propeller speed or pitch, which is the core function of the propeller governor.