Aviation accident ANC15LA015

The failure of the ball bearing within the pitch change spider assembly due to its operation with no grease within the bearing, which resulted in the subsequent fracture of the spider assembly and a loss of tail rotor control authority. Also causal to the accident were the overhaul facility’s failure to follow the helicopter manufacturer’s spider assembly overhaul procedures, which resulted in the assembly leaving the facility with no grease in the bearing, and the mechanic’s failure to complete all of the tasks on the 600-flight-hour/24-month inspection checklist, which led to the lack of grease in the bearing going undetected.