What happened
On February 11, 2015, an Eurocopter AS 350 B3, registration HB-ZIG, was conducting a commercial transport flight under visual flight rules near Meiringen, Switzerland. The mission involved transporting two workers for the Kraftwerke Oberhasli AG (KWO) from one facility to the Grubenbachfassung installation.
As the aircraft approached the target, the pilot noted that the landing area on the building's roof was extremely confined. Due to a snowdrift on the larger, lower section of the roof that appeared unstable, the pilot attempted to land on the smaller, upper platform. During the approach, the pilot observed rising terrain and bushes ahead. As the aircraft descended, the pilot attempted to abort the landing by increasing collective pitch. However, during this maneuver, the main rotor struck a rock formation located to the right of the aircraft. The impact caused the helicopter to rotate clockwise and tip onto its right side, coming to rest on the edge of the roof platforms and the sloping terrain. All four occupants—the pilot, a flight assistant, and two passengers—were uninjured and successfully evacuated from the wreckage.
The investigation
SUST examined the circumstances surrounding the landing at the Grubenbachfassung site. The investigation established that the aircraft was within weight and center of gravity limits, and no technical malfunctions were found in the engine or rotor systems. The investigation also looked into the familiarity of the crew with the site, noting that neither the pilot nor the flight assistant had previously landed at this specific location. Furthermore, the investigators reviewed the information available to the crew, including verbal accounts from workers who had previously used the roof for similar drop-offs.
Findings
- The primary cause of the accident was the main rotor making contact with an obstacle because the pilot attempted to land in a site with insufficient clearance.
- The crew members were performing their first landing at this specific location.
- There was a lack of pertinent, detailed information regarding the specific constraints of the landing site.
- Previous experience shared by workers suggested that landings on the roof were possible, which influenced the decision to attempt the landing.
- The physical dimensions of the upper platform were too small to allow for a safe landing without rotor interference from the adjacent rock and vegetation.