The helicopter pilot reported that, after a high reconnaissance the helicopter was descended to about 30 ft above the power lines for the powerline inspection, while flying about 30-35 knots. While patrolling, they climbed over an identified crossing line, and then descended back down. During the decent , the passenger spotted a previously unseen power line in their flight path so the pilot "pulled hard aft cyclic with right pedal" but the main rotor blades struck the power line. The helicopter acquired a vibration in the main rotor system, but pilot was able to land without further incident.

The helicopter sustained substantial damage to the main rotor blades.

The pilot reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation.