Facts
On 18 January 2018 at 1505 local time, an Airbus Helicopters AS 350 B3 (registration LN-OST, year of manufacture 2016, engine Turbomeca Arriel 2B1) operated by Pegasus Helicopter AS was conducting a power line inspection for Agder Energi Nett. The flight was a specialised operation (SPO) under visual meteorological conditions in daylight. The crew consisted of the pilot and two observers from the power company. No injuries or damage to the helicopter were reported.
Sequence of Events
The pilot began his duty at 0800, departed Stavanger Airport Sola at 0850, and met the observers at Kvinesheia. After a safety job analysis, they completed a 2.6-hour inspection, followed by a 35-minute break and a shorter session. After the planned mission, they were assigned to inspect a 22 kV line in an unfamiliar area near Marnardal. The observers used a digital map on an iPad that did not include crossing lines. The pilot used a fixed iPad with the Air Navigation Pro app, which did show crossing lines.
While flying approximately 30–40 m above the 22 kV line northbound, the line turned right. The pilot climbed to avoid tall pine trees to the right. As he lowered the collective to return to the original altitude, he spotted a crossing power line ahead and to the right. He instinctively lowered the collective further to fly under it. The crossing line was concealed by terrain and trees; its left mast was hidden behind a hilltop and the right mast partially obscured by pines. The pilot estimated his speed at 25–30 kt and the distance to the line at 50 m when he detected it.
At the time, the pilot had zoomed in on his electronic map to follow a branch line, and the moving map function (centering the helicopter symbol) was deactivated. As a result, the helicopter symbol moved off the displayed map area, and the pilot did not see the crossing line on his screen. The observer’s map lacked crossing-line data, so he could not warn the pilot. The crossing line was not required to be physically marked because less than 100 m of it exceeded 60 m above ground.
The pilot considered the incident serious and ended the mission for the day.
Operator Actions
Pegasus Helicopter AS conducted an internal investigation and concluded that its Standard Operating Procedures (SOP) for power line inspection were adequate. However, a combination of factors left the pilot’s attention as the only barrier against collision. The company emphasized the need for physical signage at crossing lines to prevent recurrence.
Agder Energi Nett later stated that the situation was unusual, with four helicopter companies contracted to survey storm damage. They had no framework agreement with Pegasus at the time. The power company acknowledged the risk and decided to strengthen its procurement competence for helicopter services, improve training for personnel on inspections, and mark all crossing lines with signs. They also established framework agreements with selected helicopter operators.
AIBN Assessment
The Accident Investigation Board (AIBN) noted that a number of factors led to the serious incident: high external pressure on Agder Energi Nett, insufficient planning due to willingness to accommodate the customer, the crew’s unfamiliarity with the area, lack of crossing-line data on the observer’s map, loss of situational awareness from the pilot’s zoomed map, and the inconspicuous nature of the crossing line. The Board found that only luck and the pilot’s quick reaction prevented a collision. It also referenced a similar unreported incident on 13 February 2018 with Fonnafly AS and a subsequent accident on 21 June 2018 involving Heliwest that resulted in rotor blade damage (report 2019/08).