What happened
On February 14, 2024, an Airbus AS350 B3, registered HB-ZES, was performing an external sling load operation near Niouc, Switzerland. The mission involved transporting a 250 kg metal walkway from a pick-up area to a destination located 350 meters higher up a slope.
After completing a reconnaissance of the area, the pilot landed to attach the load using a 30-meter sling. During the wait for the ground crew to prepare the destination, the pilot began focusing on the subsequent mission, leading to a loss of situational awareness regarding the current task. Upon receiving clearance to depart, the pilot initiated a vertical takeoff and climbed directly toward the destination. This flight path took the aircraft directly under a 65,000 V high-voltage power line.
Although a task specialist on the ground attempted to warn the pilot via radio, the main rotor blades struck and severed two of the high-voltage cables. The impact caused significant vibrations and loss of control. The pilot attempted an emergency descent into a steep, wooded area, intentionally pitching the tail boom into the vegetation to absorb impact energy. The helicopter struck the trees and was destroyed. The pilot sustained serious injuries but managed to evacuate the wreckage unaided before a small fire broke/extinguished.
The investigation
The investigation, conducted by the BEA on behalf of the Swiss Transportation Safety Investigation Board (STSB), examined the flight data from the Helicom V2 unit, ground-based videos, and wreckage analysis. Investigators examined the state of the high-voltage lines, the condition of the rotor blades, and the engine's performance. The investigation also reviewed the operator's flight preparation procedures, the use of tablets for navigation, and the communication protocols between the pilot and the task specialists.