What happened
On April 23, 2020, a Pilatus PC-12, registration N477SS, was performing a Part 91 positioning flight when the pilot reported a loss of engine power shortly after takeoff. The pilot initially attempted to divert to Rockwall Municipal Airport, but after reporting that the power loss had stabilized, intended to return to Dallas-Fort Worth International Airport. Shortly thereafter, the pilot reported a second instance of power loss and decided to divert to Mesquite Airport (HQZ).
While performing a 360-degree turn to establish a left base for the approach at 4,500 feet, the engine lost all power. The aircraft was unable to reach the runway and impacted terrain in a muddy field short of the airport. The impact caused the wings to separate from the airframe and resulted in a small post-crash fire. The pilot sustained one serious injury and was not fatal.
The investigation
Maintenance records indicated that work had been performed on the day of the accident to address difficulty moving the Power Control Lever (PCL) into the reverse position. During that maintenance, technicians identified severe binding in the beta control cable assembly, which was subsequently cleaned, reinstalled, and rigged.
An examination of the engine and propeller assembly revealed that the beta control cable was mis-rigged. The propeller blades were found in the feathered position, and the beta valve plunger was extended beyond the chamfer face of the propeller governor. This position was consistent with a state that would shut off oil flow from the governor oil pump to the constant speed unit (CSU). Investigators found that the forward beta control cable clevis adjustment nut was rotated full aft, and the swaging ball end on the forward end of the cable was not properly secured, allowing it to rotate freely within the assembly.