What happened
On June 30, 2006, at approximately 13:31, an SA315B Lama, registration HB-XUA, operated by Heli Bernina AG, was performing support duties for an avalanche protection project near Rüggen, in the municipality of Klosters. The aircraft was tasked with transporting personnel and light equipment to assist a Kaman K-1200 helicopter working in the area.
While performing a low hover approximately 20 to 30 cm above the ground, the pilot attempted to board three flight assistants from a loading area on a steep slope. As the final passenger climbed into the cabin, the aircraft began to tilt forward and to the left. During this movement, the main rotor blades struck the hillside. The pilot attempted to compensate by adjusting the cyclic and collective controls, but the aircraft struck the ground with its skids, overturned, and came to rest on its left side. The incident resulted in two light injuries to the crew and one light injury to a passenger, while the remaining occupants were unhurt. The aircraft sustained serious damage.
The investigation
The investigation examined the operational procedures, the aircraft's technical condition, and the environmental factors at the site. Investigators found that the aircraft's mechanical systems and engine were in good working order, with no pre-existing technical failures contributing to the crash.
While the total weight of the passengers and cargo exceeded the maximum authorized limits for the cabin and the external cargo basket, the investigation determined that the center of gravity remained within prescribed limits. However, the investigation noted that the passengers were not seated in approved seats but were positioned on the cabin floor, which is not a regulatory configuration for passenger transport.
Findings
- The primary cause of the accident was the collision of the main rotor with the terrain due to the selection of an inappropriate location for passenger embarkation.
- The steep 30-degree slope created an asymmetric ground effect, which, combined with a north wind, required significant control inputs.
- The physical movement of the final passenger climbing into the aircraft created a dynamic shift that the pilot could not compensate for, as the cyclic control was already near its physical limit.
- The chosen landing orientation, while making it easier to manage doors, made it difficult for the pilot to accurately judge the clearance between the left skid and the rotor blades relative to the slope.