Incident Overview
On 13 October 2017, at approximately 11:40 local time, a workplace accident occurred during helicopter external load operations involving an Airbus AS 350 B2 helicopter, registration HB-XVM, operated by Heli Rezia AG. The helicopter was transporting prefabricated wooden and plasterboard elements from a loading area at the Tesserete sports field to a construction site in the village of Tesserete, Capriasca, Ticino. During the operation, prefabricated elements tipped over due to the helicopter's rotor downwash, seriously injuring two workers.
Sequence of Events
The flight crew consisted of a Swiss pilot (born 1967) with a commercial pilot license (CPL(H)) and 6,900 total flight hours, including 1,874 hours on type. Three flight helpers (A, B, and C) and two carpenters were involved in ground operations. After approximately 30 rotations, the helicopter landed about 50 meters from the truck to perform hot refueling. Meanwhile, the carpenters prepared the next element for transport. Flight helper A was busy refueling with his back to the truck.
Following refueling, the helicopter lifted off and moved sideways with a left yaw to position over the next element. Flight helper A approached with the two hooks of the sling. As he prepared to hand over the first hook, the element began tipping toward him and the carpenters. The apprentice carpenter was struck on the shoulder and elbow, sustaining serious injuries. The truck driver, who had been near the cab, rushed to assist but was hit on the head by two other interlocked elements that also tipped over. His helmet broke, and he lost consciousness for several seconds. The pilot observed the accident, immediately landed, and assisted with first aid and emergency calls.
Meteorological Conditions
At the time and location of the accident, weather was sunny with light winds, under the influence of a high-pressure system extending from North Africa to Central Europe.
Findings
The investigation determined that the workplace accident was attributable to the insufficient securing of the prefabricated elements, which tipped over due to the rotor downwash. Contributing factors included a systemic lack of verification of the securing of the elements and an underestimation of the tipping danger caused by downwash. Additionally, the investigation identified the following factors that contributed to the origin and development of the accident but were not considered causal: insufficient safety margin of the sling used, and improper arrangement and use of the sling.