Accident Details
On 27 June 1986, a helicopter accident occurred at Reusch, on the Bernese side of the Col du Pillon, Switzerland. The aircraft involved was a SA315B Lama, registration HB-XMR, operated by Heliswiss SA. The pilot, a Swiss national born in 1951, held a professional pilot license for helicopters and had a total of 1,430 flight hours, including 560 hours on type. The flight assistant, who held a valid Swiss aircraft controller license, had been employed by Heliswiss since 1985 as a mechanic and flight assistant with good experience in timber transport.
Sequence of Events
The pilot began timber transport operations at approximately 0900 local time from Reusch. By 1700 hours, on the 93rd rotation out of 95 planned, the helicopter was in a hover over the unloading area. The flight assistant attached a bundle of three 5-meter-long cable ropes to the 40-meter longline suspended from the helicopter's cargo hook. He then moved about 15 meters away along a path that intersected the departure axis at a right angle and radioed the pilot that it was clear to depart. The pilot initiated a left turn to leave the unloading area. At that moment, the load left the ground and the assistant observed a pendular movement of the cables swinging toward him. He tried to flee but was caught under one arm, lifted approximately 5 meters off the ground, and thrown about 25 meters, sustaining serious injuries. Despite his injuries, he managed to radio the pilot and inform him of the incident.
Investigation Findings
The investigation established that the pilot was properly licensed and authorized for the mission, though his experience in timber transport was relatively limited. The accident occurred after five and a half hours of flight, following a one-hour break at 1300. The pilot reported feeling in good condition. The helicopter had valid certificates of airworthiness, and its mass and center of gravity were within prescribed limits. The unloading area was located on a forest-edge meadow beside a drivable path. Weather conditions were excellent: clear sky, visibility over 20 km, no wind at the site, and temperature 23°C. The pilot relied on a rearview mirror to monitor the hover phase but did not see the assistant's position. The investigation noted that a vertical ascent before initiating the turn might have limited the pendular motion of the longline.
Probable Cause
The primary cause of the accident is attributed to the fact that, at the moment of departure, the helicopter was not vertically above its load when it left the ground.