Occurrence
During a mission to place marker balls on high tension wires, the helicopter pilot misjudged the distance to the wires. Consequently, a main rotor blade struck the upper guide wire of the high tension wires, severing the tail boom assembly. Following the impact, the helicopter rotated, causing the tail boom assembly to strike the high tension wires stanchion. The helicopter then plummeted uncontrollably to the ground.
Examination
Examination of the wreckage and video tape disclosed no evidence of any preexisting malfunctions or failures.
Findings
The pilot misjudged the distance from the high tension wires, leading to the rotor blade striking the upper guide wire.