What happened
On the evening of January 17, 2001, a Bell 206L-1 helicopter, registration SE-HPO, was engaged in an urgent search and rescue mission near Kåsjön, Sweden. The pilot was tasked with locating a person reported missing after an ice-skating accident. During the operation, the crew identified a hole in the ice and needed to transport a police search and rescue dog team to the site.
Because the shoreline was unstable due to thin ice, the pilot attempted a precarious maneuver by placing the left-hand landing skid on a small wooden bridge to facilitate the boarding of the dog team. The operation took place in darkness, with the pilot relying on searchlights for visibility. While the pilot believed there was a safety margin of approximately 1.5 meters between the rotor disk and nearby vegetation, the aircraft was operating below the required three-meter safety distance.
As the passengers boarded, the helicopter experienced lateral movement. The pilot subsequently felt and heard the main rotor making contact with tree branches. While the pilot initially believed the contact was minor, a post-flight inspection revealed that the tips of both rotor blades had been significantly damaged, rendering the aircraft unserviceable.
The investigation
The Swedish Accident Investigation Authority (SHK) examined the circumstances of the collision, focusing on the environmental conditions and the pilot's maneuvering. The investigation established that the mission was highly demanding, requiring low-altitude flight in darkness with limited external visual references. The investigators also reviewed the aircraft's maintenance status and the pilot's qualifications, finding both to be in order.
Findings
- The mission requirements placed significant operational demands on the pilot.
- The pilot was aware that the maneuver was being performed within a distance to obstacles that was less than the mandated safety margin.
- Due to the darkness and the specific appearance of the tree—which had darker bark and was leaning over the water—the pilot misjudged the actual distance to the obstacle.
- The lateral movement of the aircraft during the boarding process caused the rotor to strike the birch tree.