The purpose of the rotorcraft external load flight was to spray water from the helicopter and wash some outside insulators that were suspended from power line structure arms. During the wash, the crew heard a bang, and the helicopter descended into trees. A Federal Aviation Administration inspector examined the wreckage after the accident and observed substantial damage to the fuselage and rotor blades. The inspector also observed damage to the power line structure arm that was consistent with main rotor blade contact. The inspector did not find evidence of any preimpact mechanical malfunctions or failures of the helicopter, nor did the operator report any. Based on this information, it is likely that the helicopter’s main rotor struck the power line structure while the pilot was maneuvering in close proximity to it.