An in-flight failure of the engine-to-transmission driveshaft due to a fatigue fracture of the forward-most flex plate in the forward KAflex coupling that resulted from a loose bolt attachment between the flex plate and the forward driveshaft coupling. Contributing to the accident was maintenance personnel’s failure to identify the condition and remove the KAflex driveshaft for repair as specified by the manufacturer.

the pilot's failure to maintain an adequate fuel supply for the flight which resulted in a loss of engine power due to fuel exhaustion, and the loss of rotor rpm during the autorotation. The downhill sloping terrain was a related factor.