Summary
On 5 September 2000, at approximately 0915 hours local time, a SA315B Lama helicopter (registration HB-XTW) crashed in a clearing near Lac Retaud, close to the Col du Pillon, in the commune of Ormont-Dessus, Vaud, Switzerland. The pilot, who was the sole occupant, sustained fatal injuries. The accident was notified to the Federal Bureau of Aircraft Accident Investigation by the Swiss Air Rescue Guard REGA at around 0930 hours.
Accident Details
The helicopter had departed from the Glacier du Sex Rouge earlier that morning for a load transport to a field near the Col du Pillon. The pilot, who had a total flight experience of 5,198 hours, including 3,200 hours on the type, performed a slower-than-usual engine start and a two-phase hover check for vibrations before departure. During the flight, the pilot communicated that he anticipated arriving in two to three minutes. A witness near the accident site reported hearing the engine power decrease and seeing white smoke from the rear of the turbine, followed by a left rotation and loss of altitude. The helicopter crashed in a wooded area.
Aircraft Information
The helicopter was a SA315B Lama, manufactured by Eurocopter France/Aérospatiale in 1979, serial number 2537. It was powered by a single Turbomeca Artouste III B1 turboshaft engine, serial number 1093. The aircraft was registered to Air Glaciers SA and operated under VFR day and night for private use and VFR day for commercial operations. At the time of the accident, the airframe had 10,840 hours total time, and the engine 13,647 hours. The helicopter's weight was approximately 1,327 kg, well below the maximum takeoff weight of 1,950 kg. The last 100-hour inspection was performed on 18 August 2000.
Investigation
The investigation was conducted by the Federal Bureau of Aircraft Accident Investigation in collaboration with the cantonal police. The wreckage exhibited significant compression to the cabin, with the tail boom forming an approximately 90-degree angle. The main and tail rotor blades showed no deformation from rotation. Instrument readings were consistent with impact forces. Examination of warning lamps indicated that the "Pression huile G.T.M." (engine oil pressure) and "Disjonction génératrice" (generator disconnect) lamps were illuminated at impact, and the "Alarme" lamp likely as well. The collective pitch indicator showed a needle impression between 0.9 and 1.0. The ELT functioned. An autopsy revealed the pilot died from multiple major traumatic injuries, with no evidence of alcohol, drugs, or medical impairment.
Cause
The accident was caused by an unnoticed engine failure during descent. The engine failure was probably due to the ingestion of at least one piece of ice that had lodged at the rear end of an air intake.