Accident Overview
On 6 November 1987, at approximately 1330 local time, a SA 315B Lama helicopter (registration HB-XRB) crashed while approaching a landing site near Chironico, in the canton of Ticino, Switzerland. The helicopter, operated by Heli TV on behalf of Titlis Transport AG, was engaged in logging operations. The accident resulted in one passenger sustaining fatal injuries, three passengers suffering serious injuries, and the pilot sustaining minor injuries.
Flight History
Earlier that day, the pilot had conducted several logging rotations. After a lunch break in Lavorgo, the pilot departed with a flight assistant and three loggers on board, intending to carry an empty container as an underslung load to the Ces area. Upon arrival at the logging site, the ground assistant reported that he was not ready for the load. The pilot then decided to land at a known landing site situated downhill, where the helicopter was typically parked overnight. Approximately 30 seconds into the approach, with low forward speed, the helicopter crashed.
Wreckage Examination
The wreckage trail indicated that the helicopter impacted with high sink rate and a left turn. The tail boom was found severed; the tail rotor gearbox and a section of the boom were separated and located 15 meters downhill on a road. The main rotor blades showed impact marks consistent with contact with the tail rotor boom. Paint residues from the main rotor blade tip caps were found on the tail rotor shaft and boom at the separation point. The engine showed no pre-existing abnormalities; however, grass and debris ingestion suggested the engine was still running after ground impact. The main rotor gearbox was locked. All control linkages were examined and found intact.
Passenger Restraints
Post-accident inspection revealed that the passenger seat belts were in the closed position but were not worn. The pilot used his seat belt and shoulder harness, which remained intact under load. The report notes that had the passengers worn their seat belts, the serious and fatal injuries might have been avoided.
Weather Conditions
At the accident site, weather was clear with visibility exceeding 20 km. Wind was from the northwest at 5–10 knots, with gusts up to 15 knots. Temperature was 15 °C, dew point approximately 5 °C. Local foehn turbulence was possible.
Probable Cause
The investigation determined that the accident was probably due to a harsh control maneuver during the approach to the landing site, which caused the main rotor blades to sever the tail rotor boom.
Aircraft and Pilot Information
The helicopter was a single-engine, five-seat turbine helicopter (SA 315B Lama), built in 1975. At the time of the accident, its mass was approximately 1592 kg, within the maximum takeoff mass of 1950 kg. The pilot held a professional helicopter license with 829:58 total flight hours, about 750 on type. He had no medical restrictions.