What prevents a propeller from feathering automatically when the engine is shut down?

The reason that a feathering lock operated by centrifugal force prevents a propeller from feathering automatically when the engine is shut down relates to the design of the propeller and its feathering mechanism. In multi-engine aircraft, the feathering of a propeller typically occurs to minimize drag when an engine fails or is shut down. However, this process is not automatic, particularly not during an engine shutdown, because of the centrifugal force that acts on the propeller blades due to their rotation.

When the engine experiences a reduction in power and subsequently shuts down, the centrifugal force from the rotating propeller keeps the blades in a "flat" position, which is optimal for producing drag rather than a feathered position that would align the blades with the airflow and significantly reduce drag. The feathering lock mechanism relies on the centrifugal force to maintain the propeller blades in position until the pilot actively engages the feathering process, thus ensuring that the propeller does not inadvertently feather due to loss of power. This is crucial for pilots, as an unintentional feathering of a propeller could complicate flight operations and affect safety.

Understanding this mechanism is vital for pilots during checkrides and operational scenarios, as it informs them about the behavior of the aircraft during engine shutdown