What happened
On October 16, 2021, an Airbus Helicopters AS350 B3, registration LN-OGA, operated by Helitrans AS, was engaged in a commercial waste transport mission in the Lofoten region. The mission involved transporting large bags of refuse from various coastal collection points to designated landfills.
After completing several successful transport legs, the pilot attempted to return to a collection point to pick up the remaining crew. During this leg, the pilot chose a flight path through a narrow sound between Mortsundholmen and Mortsund. While flying through the passage, the 15-meter-long synthetic sling line attached to the aircraft's cargo hook made contact with an uninsulated 230V power line. The impact severed the line, causing the sling and its attached hook to fall into the sea. The pilot immediately activated the electrical release mechanism to disconnect the line and maintained control of the aircraft.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the flight path, the aircraft's equipment, and the regulatory status of the power line. The investigation confirmed that the power line, which spanned approximately 95 meters between poles, was not registered as an aviation obstacle at the time of the incident. While a maritime warning sign indicated a 15-meter height for ship traffic, the line did not meet the reporting criteria for aviation obstacles under the regulations in effect at the time.
Investigators also reviewed the pilot's pre-flight planning, which utilized digital mapping services. The investigation found that the mapping software used did not feature specific aviation obstacle layers, making the line difficult to detect during planning without a physical reconnaissance of the area.
Findings
- The power line was severed because the Airbus Helicopters AS350 B3 flew too low, allowing the 15-meter sling line to strike the wires.
- The pilot's decision to fly through the narrow sound was a departure from the safer routes used during previous legs of the mission, potentially due to a loss of focus after the primary cargo tasks were completed.
- The power line was not officially documented as an aviation obstacle, as the utility company's reporting obligations for such lines were subject to recent regulatory changes.
- The pilot demonstrated good judgment by quickly releasing the load and assessing the aircraft's stability, though an immediate landing for a technical inspection would have been the more appropriate safety response.
Safety action
- The NSIA noted that recent changes to regulations regarding the reporting of power lines as obstacles may create a period of risk during the implementation phase.
- The investigation suggests that helicopter operators should utilize mapping tools that specifically include aviation obstacle data to improve situational awareness during mission planning.