What happened
On March 4, 1997, an SA 315B Lama, registration HB-XTP, was performing a routine commercial transport mission in the Swiss Alps. The flight originated from Gsteigwiler, carrying three workers and approximately 220 kg of equipment attached as an external underslung load. The objective was to deliver materials to the Konkordiahütte.
During the flight, the pilot encountered deteriorating weather conditions. While initial reports suggested visibility was good near the destination, the aircraft encountered heavy fog and low clouds while navigating the Jungfraujoch and Mönchsjoch regions. As the pilot attempted to navigate through the terrain, visibility became extremely poor, resulting in a complete loss of the horizon and visual ground references. While maneuvering, the external load struck an ascending snow slope on the Fieschergrat glacier. The sudden resistance from the impact pulled the helicopter into the terrain, causing a violent crash.
The investigation
Investigators from the Swiss Transportation Safety Investigation Board (SUST) examined the wreckage at the accident site, located at an altitude of approximately 3,560 meters. The investigation focused on the flight path, the meteorological conditions, and the mechanical state of the aircraft. The wreckage analysis showed no evidence of technical failure; the main rotor blades were bent from the impact, and the cockpit floor was heavily deformed, indicating a high-speed, nose-down collision with the glacier.
Findings
- The pilot was a licensed professional with significant experience on this aircraft type.
- The aircraft's weight and balance were within permissible limits, and the engine and mechanical systems were fully functional.
- The flight was conducted under Visual Flight Rules (VFR), but the pilot encountered rapidly changing mountain weather.
- The loss of visual references due to improper flight tactics led to the external load striking the rising terrain.
- The lack of a visible horizon in the white, diffuse environment prevented the pilot from identifying the approaching slope.
- The failure to jettison the external load may have contributed to the loss of control following the initial impact.
Safety action
No specific safety recommendations were recorded in this report, though the investigation highlighted the extreme danger of flying in high-altitude terrain when visibility is obscured by fog or low clouds.