Background
A construction company contracted Air-Glaciers SA to transport and place prefabricated elements for a single-story building at Euloz, in the municipality of Fully, Valais. The previous day, the wooden floor had been delivered by a different helicopter type without issues. On the accident day, operations began around 09:45 after the pilot surveyed the site.
Flight Sequence
The helicopter, a Eurocopter AS350 B3 registered HB-XQJ, initially used a 50-meter sling with two 8-meter straps (total ~58 m). After the first wall placement, the ground crew found the downwash too strong, so a 20-meter cable was added, making the total length about 78 meters. Following a pause to resolve an alignment problem between two walls, operations resumed. During the break, tensions were reported between the pilot and the flight crew.
For the south façade element weighing approximately 400 kg, the helicopter lifted it from a truck and flew to the construction site. The pilot used the "vertical reference" technique, maintaining direct visual contact with the load. The wall was set in place and held by five ground workers. After adjustments, the site foreman signaled the helicopter to release the load, and two workers inside the building began disconnecting the straps. The first strap was removed using a V-shaped stepladder. The worker then moved to disconnect the second strap.
Accident
As the second strap was released, the flight assistant (chef assistants) moved to the downhill side of the wall and expressed surprise via radio about the retrieval of transport equipment. Only three people were now holding the wall. The flight assistant guided the helicopter to pick up steel straps and guide ropes stored at the center of the site. The helicopter then departed southward toward the loading area. At that moment, the entire construction crew felt the helicopter's downwash. The south wall element tipped over downhill; the workers tried but failed to hold it. The flight assistant, positioned downhill, attempted to escape but was fatally injured when the wall fell on him.
Weather
MeteoSuisse data and pilot reports indicated variable wind of 2–4 knots at the site, with the pilot noting winds of 5–8 knots and gusts. The sky was partly cloudy, visibility over 20 km, temperature 20 °C, dew point 14 °C. Sun azimuth was 136° with an angle of 44°.
Cause
The investigation determined that the accident was caused by the airflow from the helicopter tipping over a building element, which fatally injured a flight assistant in the danger zone. Contributing was the lack of at least temporary mechanical securing of the wall element.