L2018-A1 Accident of helicopter OH-HNX in Norway on 21 June 2018
The two-man crew of helicopter OH-HNX of the Hughes 369D type, owned and operated by the company Heliwest Oy, was carrying out an inspection flight of power lines in Norway in the county of East Agder (Aust-Agder), when its main rotor hit a 132 kV transmission line crossing above the inspected 22 kV transmission line. The helicopter's main rotor was damaged in the collision, but the pilot was able to fly the helicopter back to its starting location. Agder Energi Nett company's 132 kV transmission line was cut in the collision. There were no personal injuries.
The Accident Investigations Board Norway (AIBN) investigated the incident, because the accident took place in Norway. The Safety Investigation Authority, Finland, appointed Safety Investigator Tii-Maria Siitonen as an authorised representative to the investigation, as Finland was the aviation company's operator country.
In addition to the pilot, an operator of the equipment of the subcontractor company was on board the helicopter. The database of the equipment did not include a mention of the intersecting transmission lines. Neither did the lower 22 kV transmission line have a marking warning about an intersecting transmission line. Norway's national regulations do not require the marking of intersecting lines unlike in Finland and Sweden, for example. In early 2018, two incident had occurred in Norway, where Norwegian helicopters inspecting electricity lines were close to hitting intersecting transmission lines.
Based on the investigation completed on 25 June 2019, The Accident Investigations Board Norway recommends that the Civil Aviation Authority introduce requirements for physical marking of crossing lines in Norway.