What happened
On July 11, 2005, an SA315B helicopter, registration HB-ZFU, was performing transport duties near the Cabane des Vignettes in the Valais region of Switzerland. After completing several successful rotations to deliver supplies and passengers, the pilot attempted a second rotation to drop off two passengers and a 300 kg external load.
During this flight, weather conditions began to deteriorate, with cloud cover dropping to approximately 100 meters above the hut. To ensure a quick departure before visibility worsened, the pilot positioned the aircraft on a small metallic landing platform. Due to the limited space on the 5 x 8 meter platform, the pilot oriented the aircraft into the wind, which placed the cabin door facing the hut's entrance. As the pilot prepared for takeoff, two individuals—a hut keeper and a passenger—remained on the left side of the aircraft.
While the pilot's attention was focused on the people on the left, the main rotor blades struck the front overhang of the hut. The impact caused the helicopter to pivot sharply, leading the tail rotor to strike the building as well. The aircraft overturned and slid approximately 20 meters down the glacier, landing upside down. The pilot escaped the wreckage uninjured.
The investigation
The investigation examined the technical condition of the aircraft, the operational environment, and the meteorological factors present at the time of the accident. Investigators found no mechanical defects in the HB-Z15B; the aircraft had recently undergone a major overhaul. The investigation also analyzed the dimensions and layout of the landing platform, noting its proximity to the hut's structure and the lack of safety netting.
Findings
- The primary cause of the accident was the collision of the main rotor with an obstacle during takeoff from an undersized platform located too close to the hut.
- The pilot's attention was diverted toward the individuals on the left side of the aircraft, causing him to lose situational awareness regarding the proximity of the roof on the right.
- Deteriorating weather conditions created psychological pressure on the pilot to depart the site as quickly as possible.
- The landing platform's dimensions (5m x 8m) were insufficient to allow for safe passenger and crew movement without placing people in the immediate rotor path.
Safety action
- The investigation identified a significant safety deficiency regarding mountain landing platforms, noting that the lack of safety netting and the proximity to buildings pose unacceptable risks to both flight crews and ground personnel.
- A safety recommendation was issued for the Federal Office of Civil Aviation to mandate specific safety standards for mountain platforms, including minimum dimensions, required distances from obstacles, and the installation of protective netting.