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."