Accident Sequence
On the afternoon of 15 December 1993, the pilot of a SA 315B "Lama" helicopter, registration HB-XTM, departed Grindelwald carrying an external load for a construction site on the Jungfraujoch. After delivering the load and loading materials, the pilot departed Jungfraujoch around 1530 hours with three passengers, intending to land at the Eigergletscher station. During the approach, the pilot observed a snowdrift approximately 20 meters west of the station. To avoid the snowdrift, he planned to touch down on an area between the snowdrift and the station. After initial ground contact with the landing skids, the pilot increased collective pitch to lift the helicopter slightly and reposition it forward. At that moment, a gust of foehn wind from behind pushed the helicopter approximately two meters forward, causing the main rotor blades to strike a protruding concrete wall of the building.
The three passengers exited the helicopter unharmed. The helicopter sustained damage to the main rotor blades.
Findings
The pilot held a valid professional pilot license and had sufficient experience for such transport. The helicopter was airworthy and within weight and balance limits. The landing area on the southwest side of the Eigergletscher station was snow-covered. Weather conditions included foehn winds with turbulence; the wind was from southeast at 15 knots with gusts up to 35 knots, and the pilot reported turbulent winds from 180° to 240°. Technical malfunction was ruled out as a cause.
Causes
The investigation determined the accident was due to:
- Landing with insufficient safety distance from a building;
- Underestimation of the wind influence.