What causes an uncommanded propeller feather?

An uncommanded propeller feather occurs when the propeller unexpectedly moves into a feathered position, which can lead to a loss of thrust and control issues. The malfunctioning feather dump solenoid is critical in this scenario because it is responsible for regulating the movement of the propeller blades into and out of the feathered position. If this solenoid fails, it could inadvertently cause the propeller to feather without command from the pilot or other systems. This mechanical failure is a direct cause of the uncommanded event, making it the most accurate choice for this specific question.

In contrast, while electrical malfunctions can impact various systems, they are less likely to explicitly cause a propeller to feather without pilot input. Fuel starvation generally affects engine performance and thrust but would not directly lead to an uncommanded feathering of the propeller. Excessive engine temperature could lead to other issues, but it is not a primary factor in causing a propeller to feather unexpectedly.

Thus, the malfunctioning feather dump solenoid is the most relevant factor in leading to an uncommanded propeller feather situation.