What happened
On September 21, 2015, an Airbus Helicopters AS 350 B3, registration LN-OGL, was conducting an aerial survey mission for the Norwegian Geological Survey (NGU) near Lagovaggi, Norway. The mission involved flying a specialized probe suspended approximately 30 meters beneath the aircraft. To ensure accurate data collection, the pilot was required to maintain a relatively constant altitude of roughly 60 meters above the terrain while following pre-defined flight lines.
During the operation, the aircraft was navigating terrain with significant elevation changes. As the crew approached the Skjomtinden mountain area, the pilot focused on maintaining altitude relative to the cloud base, which was barely above the highest peaks. While descending into a valley, the onboard equipment operator alerted the pilot to a high-voltage power line ahead, using a paper map for reference. However, the pilot encountered the line much sooner than anticipated. Despite an attempt to maneuver away, the suspended probe became entangled with the power line, which was positioned 58 meters above the ground. The pilot, flying at approximately 97 meters, successfully released the probe using both electrical and mechanical release mechanisms and subsequently landed the aircraft safely.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the flight procedures, the crew's workload, and the equipment used for navigation. The investigation looked into the disparity between the pilot's experience level and the company's operational requirements, as well as the effectiveness of the communication between the pilot and the sensor operator.
Findings
- The pilot was managing a high workload due to the complexity of maintaining precise altitude and flight paths over varying terrain.
- The pilot had been granted a dispensation from the company's standard requirement of 1,000 helicopter flight hours, as the pilot possessed 880 total hours.
- The cloud base was lower than the minimum altitude requirements specified in the operator's manual, which likely increased the pilot's cognitive load.
- A discrepancy in situational awareness existed between the pilot and the operator; the pilot relied on a GPS-based indicator, while the operator used a paper map, leading to different perceptions of the aircraft's position relative to obstacles.
- The power line was encountered much closer than expected, leaving insufficient time for an effective avoidance maneuver.
Safety action
Following the incident, HeliScan AS and NGU updated their equipment, providing the operator with an iPad running AirNav Pro software to replace paper maps. Additionally, plans were discussed to upgrade the GPS-based indicator to include automated warning zones, which would display red lines around known obstacles to alert the pilot when approaching hazards.