What happened
On March 23, 2026, Fjord Helikopter AS was conducting commercial power line construction work near Heggjabygda in Stad municipality. The operation involved transporting composite masts from a rigging site to an installation point approximately 9 kilometers away using an Airbus Helicopters AS 350 B3 with registration LN-OVB. One person was on board, and there were no injuries or damage to the aircraft.
The pilot and a task specialist performed a pre-flight safety analysis and adjusted the ground crew's plan, increasing the number of personnel receiving the mast from two to three. The sling was attached to the load hook by a contractor employee while the task specialist observed. During the flight, the pilot noted that the composite mast began to pendulum at 20 knots. After traveling about 6.5 kilometers, the pilot felt a jerk and the helicopter rose slightly. Looking down, he saw the mast falling into steep terrain.
Upon returning to the rigging site, the crew found the sling intact but damaged at the point where it had been attached to the hook. The load hook was removed from service and sent to the manufacturer for inspection.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined several potential causes for the loss of the suspended load. These included a failure of the sling, a technical defect in the load hook, an accidental release by the pilot, incorrect attachment of the sling, or the sling twisting out of the hook.
Technical inspection by Select Helicopter Services Ltd found no faults with the load hook. The pilot confirmed he did not accidentally trigger the two-stage release mechanism on the cyclic stick. NSIA assessed that the sling was likely attached correctly, as both the ground crew and the task specialist observed proper engagement. Furthermore, an incorrectly attached sling would typically have slipped off during the initial lift or shortly thereafter.
Findings
NSIA concluded that the most probable cause was dynamic movement of the mast during transport. The authority determined that the upper section of the load sling likely swung up and lay over the latch tip on the outside of the locking pin. The weight and motion of the load then pressed the locking pin inward, causing the sling to disengage from the hook.
The investigation noted that composite masts exhibit different flight characteristics compared to wood or metal, described by the pilot as a "jerk and snap" pendulum motion. The longer-than-usual transport distance increased the likelihood of the sling interacting with the latch tip. Damage found on the sling at the attachment point was consistent with pressure against the locking pin or wear from the pin while the sling was in the hook gap.
Safety action
Fjord Helikopter AS implemented several measures following the incident. The company introduced a control screen during composite mast flights to reduce pendulum movements. Additionally, they developed a method involving drilling two holes in the top of the mast to attach two separate slings, providing redundant security. NSIA also noted that industry stakeholders are developing training courses for external personnel involved in helicopter operations to improve safety standards.