What happened
On April 16, 2016, an Air-Glaciers EC135 T1 helicopter, registration HB-ZRK, was dispatched from Lauterbrunnen to the Jungfraujoch mountain landing site to assist with a medical emergency involving a tourist. The pilot, seeking to assess the wind conditions at the landing site, performed a reconnaissance flight.
During a second low-level pass at approximately 10 to 20 meters above the terrain, the pilot initiated a right-hand turn to reposition for the landing. While maneuvering near a rock spur, the aircraft's indicated airspeed dropped abruptly to zero, accompanied by a sudden increase in the rate of descent. Despite the pilot's immediate attempt to increase collective pitch and maintain forward movement, the aircraft could not maintain altitude and made contact with the deep powder snow in a running landing. The crew, consisting of the pilot, a doctor, and a medical crew member, remained safe, though the medical crew member sustained minor back injuries.
The investigation
SUST examined the flight dynamics and environmental conditions at the time of the incident. The investigation focused on the aircraft's performance capabilities at high density altitude and the impact of local wind patterns. Investigators reviewed the pilot's flight preparations, including the mass and balance calculations and the hover out of ground effect (HOGE) performance assessments conducted prior to departure. The investigation also looked into the aerodynamic effectiveness of the Fenestron tail rotor at high altitudes and the specific wind measurements recorded at the Jungfraucoch station.