What does feathering a propeller primarily accomplish?

Feathering a propeller primarily accomplishes the prevention of engine over-speed, making it a crucial safety feature in multi-engine aircraft. When a propeller is feathered, its blades are adjusted to align with the airflow, significantly reducing drag. This action minimizes the risk of engine over-speed during scenarios such as engine failure, where a windmilling propeller could generate excessive drag and cause the operating engine to work harder, potentially leading to critical failure.

By feathering the propeller, pilots can effectively manage the aircraft's performance and maintain control, ensuring that the remaining operational engine is not subjected to unnecessary strain. The feathering mechanism is particularly vital during various emergency situations, enhancing overall flight safety.