NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The purpose of the flight was to perform low-level aerial surveillance of power transmission lines using an external gimbal-mounted infrared camera to detect problems with the patrolled power lines. While patrolling above a power line that passed through a valley, the helicopter struck another power line that crossed perpendicular to the helicopter’s flightpath and was at a higher elevation than the patrolled power line and ran from poles mounted atop higher terrain. The struck power line was not marked with high-visibility balls nor was it required to be. The sun was directly in front of the helicopter and 30 degrees above the horizon at the time of the accident, which likely made it difficult for the pilot to see the crossing wire. Postaccident examination of the helicopter did not reveal any preimpact anomalies. Given that this was a low-level surveillance flight of power transmission lines, the pilot should have familiarized himself with the power lines he was going to patrol and any other wires or obstructions in the area before the flight. It is likely that he did not adequately plan for the flight and that, if he had, he might have been aware of the power line and been able to avoid it.