Flight History
On 5 August 1986, a SA315B Lama helicopter, registration HB-XLT, operated by Air Glaciers, departed from Lauterbrunnen for a supply flight to the Mönchsjochhütte. After delivering a load, the pilot picked up a net containing empty bottles and other waste weighing approximately 250 kg. While descending past the Guggihütte on the north face of the Mönch, the helicopter suddenly began to rotate around its vertical axis. The pilot jettisoned the external load and transmitted the message "I am flying to my death" over the radio. The helicopter struck rocks about 400 meters lower, overturned, and came to rest on a debris slope at an elevation of 2300 m. The pilot, the sole occupant, sustained fatal injuries.
Aircraft Information
The helicopter was an Aérospatiale SA315B Lama, serial number 2020/13, rebuilt from parts of a damaged helicopter in 1985. It was powered by a Turbomeca Artouste IIIB turbine engine. The airframe had accumulated 2476 total hours, with 351 hours since the rebuild. The last official inspection occurred in October 1985, with 100-hour and 25-hour checks on 12 July and 28 July 1986, respectively.
Pilot Information
The pilot, a Swiss citizen born in 1959, held a professional helicopter pilot license with ratings for the accident type, night flight, and mountain operations. He had 1138 total flight hours, primarily on Lama and Alouette III, including 174 hours in the last 90 days (124 on the accident type).
Meteorological Conditions
The weather was influenced by a weak high-pressure system with some northerly blocking over the Alps. In the accident area, sky cover was 2-8/8 with a cloud base around 1200 m and an upper limit near 2300 m. Visibility exceeded 10 km outside clouds. Wind was light from the north. Temperatures ranged from 18°C in the valley to 4°C at 3600 m. Pressure was 1023 hPa QNH.
Wreckage and Examination
The wreckage was scattered over 300 m on rocky terrain below the Eiger Glacier. Key components included the pilot seat, right skid, turbine, left door, main wreckage (cabin floor, main rotor, transmission), tail boom, and tail rotor assembly. The first impact point was 70 m above the main wreckage. The pilot's jacket, found torn, was located 150 m above. The external load net and its contents (empty butane bottles and plastic bags) were found 500 m east on the glacier. Examination of the tail rotor showed all three blades broken at the root; one blade had no deformation but bore traces of a soft foreign object (polyamide, matching the jacket lining) on its leading edge. The tail rotor gearbox had fractured attachments, and the rear V-struts were broken. The right door was fragmented into five parts, two with collision marks from a main rotor blade. The door handle, secured with a nylon strap and carabiner to prevent inadvertent opening, was missing. The door hinge system (designed for emergency jettison) was functional, but the safety wire on the emergency release lever was missing.
Pathological Findings
External examination indicated death due to severe injuries, particularly to the head. Blood alcohol analysis showed 0.02‰, considered negligible. The pilot was wearing a seatbelt but no helmet; seat and harness anchorages failed on impact.
Probable Cause
The accident is due to the pilot losing control of the helicopter in mountainous terrain after the tail rotor and its gearbox detached from the tail boom, and being unable to avoid collision with the terrain. The in-flight damage resulted from the defective mounting of the right door and the pilot's anorak being blown into the tail rotor.