Primary finding
Probable cause
The pilots failure to follow written instructions in the flight manual for an engine failure, and the improper use of flight controls (cyclic/collective) during an autorotation resulting in a hard landing, and collision of the main rotor blades with the tailboom assembly. Contributing to the accident was the improper installation of circlips on the counterweight assembly during an engine overhaul. This resulted in a subsequent total failure of the number 5 connecting rod.