What is a key indicator of an uncommanded propeller feather?

An uncommanded propeller feather refers to a situation where the propeller blade angle increases inadvertently, typically due to a mechanical failure or system malfunction. In this scenario, several indicators arise that help identify the issue.

Increased RPM occurs because when the propeller feathers, it reduces its effectiveness in providing thrust. As a result, the aircraft's engine might spin up to a higher RPM, especially if the propeller is no longer providing the necessary resistance against the engine’s power.

Surge in torque is another indicator since when the propeller loses its ability to produce thrust effectively, it can cause changes in the load on the engine. This variation can manifest as a surge in torque, which is critical to monitor during flight operations.

A decrease in thrust is a direct consequence of the propeller feathering. Feathering reduces the aerodynamic efficiency of the propeller, leading to an overall drop in thrust output. This loss of thrust can impact the aircraft's performance and handling characteristics significantly.

The combination of all these factors provides a clear indication that there is an uncommanded feathering situation. Therefore, recognizing all these signs together is essential for pilots and operators to diagnose and address the situation properly.