FAA Powerplant Written Practice Test

During the on-speed condition of the propeller, what is balanced?

1. Centrifugal force of the governor flyweights vs. propeller thrust

2. Centrifugal force of the governor flyweights vs. speeder spring tension

3. Engine RPM vs. propeller pitch

4. Airspeed vs. blade angle

The correct answer is: Centrifugal force of the governor flyweights vs. speeder spring tension

In the context of propeller operation, particularly during the on-speed condition, it is crucial to understand the interplay between the governor flyweights and the speeder spring. At this specific condition, the centrifugal force generated by the governor flyweights is balanced against the tension of the speeder spring. When the engine reaches a certain RPM, the centrifugal force acting on the flyweights increases. This force pulls the flyweights outward, causing the governor to take action to adjust the propeller's blade angle. If the RPM is increased above the governor’s set point, the force on the flyweights will exceed the tension of the speeder spring, which in turn will lead to a decrease in blade angle to throttle back the engine power and maintain the desired RPM. Conversely, if the engine RPM drops below this set point, the spring tension dominates, and the governor will increase the blade angle to allow more thrust and bring the RPM back up to the desired level. This balance is essential for maintaining a stable operation of the propeller and engine configuration, ensuring optimal performance and efficiency. Understanding this relationship helps mechanics to diagnose issues with propeller governors effectively and to ensure safe operation of the aircraft.