Incident Overview
On June 15, 1975, an SA 315 B Lama helicopter with the registration HB-XEN crashed into a steep rock face approximately 400 meters southwest of Chelenlücke in the canton of Uri, Switzerland. The accident occurred at an altitude of 3,180 meters. The pilot and two passengers on board were killed, and the aircraft was destroyed.
Operational Context
The helicopter was operated by Heliswiss for the Swiss Air Rescue (Schweiz. Rettungsflugwacht). The mission involved a search flight for a missing alpinist who had been reported absent from the Tierberglihütte. The pilot departed from the Hotel Steingletscher helipad with two mountain guides on board. Witnesses observed the helicopter flying along the Gwächtenhorn ridge before disappearing behind the Tierberglücke in westerly-southwesterly direction.
Aircraft and Crew Details
The aircraft was a single-engine, five-seat helicopter manufactured by Société Nationale Industrielle Aerospatiale. It was equipped with a Turbomeca Artouste III B engine. The pilot held a commercial license and had over 795 hours of experience on the specific model. The two passengers were mountain guides without flight training.
Investigation Findings
The investigation concluded that the exact cause of the accident could not be definitively established. However, two probable hypotheses were identified: a collision with terrain while in clouds, or a loss of control following damage to the main rotor caused by a bird strike. Evidence at the crash site included three horizontal scratch marks on a vertical rock face made by the main rotor blades. Additionally, a torn bird carcass was found near the site over a year later, supporting the bird-strike hypothesis. The pilot's actions in failing to contact his companions earlier were noted as an indirect contributing factor.