What happened
On January 18, 2018, an Airbus Helicopters AS 350 B3, registration LN-OST, was conducting a power line inspection in the Marnardal municipality of Norway. Operated by Pegasus Helicopter AS, the mission was commissioned by Agder Energi Nett to assess damage caused by recent heavy wind and snow.
While flying approximately 30–40 meters above a 22 kV line, the pilot maneuvered the aircraft to maintain clearance from nearby trees. During this maneuver, the pilot discovered a crossing power line directly ahead and to the right. To avoid a collision, the pilot had to perform an instinctive and sudden descent to pass beneath the unexpected wires. The crossing line was difficult to detect because the supporting masts were partially obscured by terrain and forest vegetation.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the circumstances leading to the encounter. The investigation found that the crew had been tasked with an unplanned mission to inspect a different area due to urgent needs. While the crew had reviewed digital maps on an iPad, the specific crossing line was not included in the observer's map data.
Furthermore, the pilot was using the Air Navigation Pro application for situational awareness. However, because the pilot had zoomed in on a specific branch of the line, the "moving map" function had not been reactivated. Consequently, the aircraft symbol had drifted off-center, and the pilot lost the ability to see the approaching crossing line on the digital display. The observers on board were also unable to provide warning as the hazard was not marked on their available digital resources.
Findings
- The primary cause of the near-miss was the failure to maintain situational awareness regarding the crossing power line due to both visual and digital limitations.
- The pilot's digital map failed to provide adequate warning because the tracking function was not active, and the aircraft's position had moved out of the visible map area.
- The crossing line was difficult to visually identify because the masts were obscured by trees and hills.
- The mission planning was compromised by external pressure to complete urgent inspections, leading to a lack of familiarity with the new flight area.
- The observers lacked the necessary map data to identify the hazard and were not trained or equipped to detect the crossing line in this instance.
Safety action
Following the incident, Agder Energi Nett committed to improving safety by implementing physical signage on power lines before crossing points. The company also moved toward establishing formal framework agreements with helicopter operators and improving the training and selection of observers for line inspections. Additionally, the utility provider is considering the use of gyro-stabilized video equipment to allow inspections to be conducted at safer altitudes.