NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.
The helicopter began the power line aerial observation flight near its maximum gross weight. As the pilot maneuvered the helicopter into an out-of-ground-effect hover with a 12-knot left crosswind, a nose-right yaw ensued that could not be corrected with a full left pedal application. Despite other remedial actions taken by the pilot, the helicopter descended to ground contact where the occupants egressed, but the helicopter was later destroyed by post-crash fire. The pilot stated there were no mechanical anomalies that would have precluded normal operation. He said, "It was an aerodynamic issue, not a mechanical issue."
FAA Advisory Circular (AC) 90-95, Unanticipated Right Yaw in Helicopters stated, "Any maneuver which requires the pilot to operate in a high-power, low-airspeed environment with a left crosswind or tailwind creates an environment where unanticipated right yaw may occur."