NTSB final report: Robinson R44 Raven II C-FICL
Analysis
The Canadian certificated commercial helicopter pilot was conducting a cross-country delivery flight with a non-rated passenger occupying the copilot seat. The passenger and pilot together had previously made delivery flights from the Robinson factory to Canada. Two witnesses saw the helicopter just before it impacted the ground and reported that the tail boom had separated from the fuselage. No witnesses were identified who saw the initial breakup sequence. Both main rotor blades were bent downward at significant angles, with one blade having penetrated the cabin on the right side with a downward slicing front to rear arc. The primary wreckage debris field was approximately 500 feet long on an easterly heading. The helicopter sustained damage consistent with a high-energy, fuselage level, vertical ground impact. Detailed post accident investigation of the engine, the airframe, and the control systems disclosed no evidence of any preimpact anomalies. The removable cyclic was installed on the left side copilot's position, contrary to manufacturer's recommendations when a non-rated passenger is seated in the left seat. The removable pedals and collective for the left side were not installed. The cyclic controls for both the pilot's and copilot's positions were broken from their respective mounting points. The copilot's cyclic grip exhibited inward crushing. The Safety Board adopted a Special Investigation Report on April 2, 1996, following the investigation into R22 and R44 accidents involving loss of main rotor control and divergence of the main rotor disk, which included a finding that the cause of the loss of main rotor control in many of the accidents "most likely stems from a large, abrupt pilot control input to a helicopter that is highly responsive to cyclic control inputs."
Probable Causeand Findings
The National Transportation Safety Board determines the probable cause(s) of this accident to be:
a loss of control and the divergence of the main rotor blade system from its normal rotational path for undetermined reasons.