DH-8-100 Propeller Control Unit Involved In An Inadvertent Feather Event
On July 25, 2013, an inadvertent feather event occurred shortly after takeoff on a DeHavilland DHC-8-100 series aircraft. Flight data records indicated that the #1 PCU beta switch was closed and lit during takeoff when a beta condition did not exist. During this event, the switch remained closed as the propeller transitioned above the ground handling range during takeoff. This condition resulted in a propeller over-torque when the aircraft’s beta backup system became active and commanded the propeller to feather while the engine was in a high-power condition.