Accident Summary
On August 2, 2004, at approximately 11:15 local time, an Eurocopter AS350B3 helicopter, registration HB-ZCB, was damaged when its tail rotor struck a wooden fence post during a landing maneuver on a forest path at Col de Jaman, in the commune of Montreux, Switzerland. The pilot, the sole occupant of the helicopter, was not injured.
Aircraft and Crew
The helicopter was an AS350B3 manufactured by Eurocopter Aérospatiale, operated by Hélicoptère Service SA, and owned by Dreieck Leasing SA. The pilot held a commercial pilot license for helicopters (CPL(H)) and a mountain landing endorsement. He had logged 5778:04 total flight hours, including 470:28 hours on the accident type. The flight was a commercial VFR operation for concrete transport.
Flight History
The helicopter departed from its base in Leysin around 07:50 and conducted multiple rotations between a concrete mixing station at Col de Jaman and a ski-lift construction site at Montagne d'Amont. During the final rotation, the pilot deposited a concrete bucket near a forest path, then returned to hook the bucket and pick up the flight assistant and the site manager. After the assistant hooked the bucket without issue, the pilot began to land on the forest path to board the two individuals.
Accident Sequence
While at about 1.5 meters above ground, the flight assistant radioed the pilot that the left skid was positioned directly above a rock block on the left side of the path and advised a maneuver to the right. During the rightward lateral movement, the tail rotor struck a wooden post of a fence running along the right side of the path. The pilot immediately landed the helicopter. The helicopter sustained damage to the tail boom, tail rotor, and tail rotor transmission. The fence suffered minor damage.
Findings
- The helicopter had no pre-existing technical defects; its airworthiness certificate and registration were valid. The last 500-hour airframe and 200-hour turbine inspections were completed on July 9, 2004.
- Fuel remaining was approximately 115 liters of Jet-A1. Mass and center of gravity were within limits. Performance at the altitude (1580 m) and temperature was adequate both in and out of ground effect.
- The pilot had not conducted a prior ground reconnaissance of the landing area. The chosen landing zone was a forest path with obstacles on both sides: a rock block on the left and a fence on the right.
- The flight assistant, who had started working for the operator in May 2004, received no documented training regarding assistance in landing site selection. The operator's Flight Operations Manual did not specify the assistant's responsibilities for safety in landing area decisions.
- Weather conditions were calm, with no significant wind, and the pilot was not dazzled by sunlight.
Cause
The accident was caused by a lateral displacement of the helicopter to the right during the final landing phase, resulting in the tail rotor contacting a fence near the landing area. Contributing factors were inadequate selection of the landing area and deficient assistance to the pilot.