What happened
On November 14, 2018, an Airbus Helicopters AS 350 B3, registration LN-OAN, was engaged in a specialized mission near Svanvik, Norway. Operated by Heli-Team AS, the aircraft was tasked with dismantling a 45-meter-high telecommunications mast. The operation involved lifting nine individual sections of the structure using a longline and transporting them to a nearby landing zone.
During the removal of the second lowest section of the mast, the helicopter's main rotor blades struck the top of a spire on an adjacent, newly erected 48-meter mast. The impact caused immediate damage to the rotor blades. The pilot promptly aborted the mission, released the longline hook, and proceeded to an emergency landing at a pre-arranged gravel pit approximately 550 meters away. During the transit to the landing site, vibrations caused by the rotor damage intensified, but the pilot successfully landed the aircraft without further complications or injuries to the crew.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the technical aspects of the aircraft, the environmental conditions, and the operational planning. The investigation focused on the proximity of the adjacent structure and the calculations used to determine the necessary length of the longline. Investigators also reviewed the Safe Job Analysis (SJA) conducted prior to the mission, which had addressed the complexities of the mast's unique horizontal bolt construction and the presence of nearby obstacles.
Findings
- The primary cause of the incident was the use of a longline that was too short for the specific task.
- Calculations for the longline length were based on a mast height of 45 meters, failing to account for the 48-meter height of the adjacent structure.
- The pilot's attention was momentarily diverted when the hook initially landed between guy wires during the first attempt at positioning.
- The crewman on the ground was positioned in a location where the spire of the adjacent mast was not visible to him.
- There were no mechanical failures found in the Airbus Helicopters AS 350 B3 or any irregularities with the pilot's certifications.
Safety action
The NSIA issued two safety recommendations directed at the Civil Aviation Authority. The findings suggest that the industry's risk assessment and Safe Job Analysis (SJA) processes must be robust enough to identify all potential hazards, specifically regarding the required safety margins between the aircraft and nearby structures. The authority recommends that oversight bodies verify that SJAs are sufficiently comprehensive to act as an effective barrier against such operational errors.