What happened
On May 14, 2003, during an emergency medicine certification course in the La Stampa area of Cadro, Switzerland, an Agusta A109K2 helicopter, registration HB-XWH, performed a demonstration of its rotor downwash. The flight was part of a scheduled static presentation of medical equipment by the REGA air rescue service.
As the helicopter approached the landing site, the group of participants was moved toward a retaining wall to better observe the airflow effects under existing wind conditions. While the aircraft was in a hover approximately 8 to 10 meters above the ground, the force of the rotor downwash pushed a participant toward the edge of the landing area. The individual was propelled over a low retaining wall, falling approximately 1.5 meters onto an adjacent access road. The fall resulted in severe injuries to the person's spine and left hand.
The investigation
The investigation examined the flight operations, the site selection, and the coordination of the ground participants. It was established that the flight was authorized as a non-operational flight for demonstration purposes. While the landing area itself was suitable for a static display, the investigation focused on the specific positioning of the participants during the active downwash demonstration. Technical inspections of the Agusta A109K2 revealed no pre-existing mechanical defects that contributed to the event. The pilot was found to be properly licensed and experienced in performing similar demonstrations at this location.
Findings
- The primary cause of the accident was the selection of an unsuitable location for the rotor downwash demonstration, specifically the proximity to a retaining wall.
- The force of the downwash was sufficient to displace a person of relatively light weight (approximately 55 kg) over the physical obstacle.
- A contributing factor was the inadequate supervision and management of the participants on the ground during the demonstration.
- Environmental factors, including a 15-knot wind with 25-knot gusts, influenced the movement of the group and the dynamics of the airflow.