If the Primary Prop Governor fails, what could happen to the prop RPM?

When the Primary Prop Governor fails, the propeller's RPM could overspeed or feather. The governor is responsible for regulating the propeller speed by adjusting the blade pitch, and if it fails, it can no longer control this function effectively.

In the event of a governor failure, the propeller blades may be pitched for maximum performance, potentially allowing them to overspeed beyond their normal operational limits. This overspeed condition can put excess stress on the engine and propeller, leading to possible mechanical failure or damage. Additionally, if the propeller feathers – which refers to the blades being turned to a position that minimizes drag – it can result from the failure of the governor to maintain the appropriate pitch for flight conditions.

In essence, the correct answer reflects the reality that without the governor's control, the propeller could operate outside its safe RPM range, leading to significant operational risks.