In a constant-speed propeller, what happens to engine RPM when blade angle increases due to reduced governor spring tension at fixed throttle?

In a constant-speed propeller, what happens to engine RPM when blade angle increases due to reduced governor spring tension at fixed throttle?

• A. RPM decreases
• B. RPM increases
• C. RPM stays the same
• D. RPM fluctuates

Answer: (A)

In a constant-speed propeller system, the governor continuously adjusts blade pitch to hold the engine at the selected RPM. If the blade angle increases, the propeller presents a heavier load to the engine because coarser pitch resists turning and requires more torque to maintain speed. With the throttle fixed, the engine cannot deliver more power to meet that increased load, so the engine RPM falls. The governor would normally try to bring the speed back up by reducing pitch or increasing fuel, but the described condition—blade angle rising due to lower governor spring tension—leads to a lower RPM.

In a constant-speed propeller system, the governor continuously adjusts blade pitch to hold the engine at the selected RPM. If the blade angle increases, the propeller presents a heavier load to the engine because coarser pitch resists turning and requires more torque to maintain speed. With the throttle fixed, the engine cannot deliver more power to meet that increased load, so the engine RPM falls. The governor would normally try to bring the speed back up by reducing pitch or increasing fuel, but the described condition—blade angle rising due to lower governor spring tension—leads to a lower RPM.