Agusta A109K2 HB-XWM Collision with Cable in Brändlen

Incident Overview and Aircraft Details On May 12, 2008, at approximately 14:45 local time, an Agusta A109K2 helicopter, registration HB-XWM, operated by Schweizerische Luft-Ambulanz AG, was involved in an accident in Brändlen, Gemeinde Wolfenschiessen/NW, located about 18 km south-southeast of Luzern, Switzerland. The aircraft, a twin-engine multi-purpose helicopter manufactured by Giovanni Agusta S.p.A. in 1994, was on a commercial visual flight rules (VFR) mission. The helicopter sustained damage to its fuselage and nose gear, with one main rotor blade severely damaged and the main rotor gearbox overloaded. The cable involved in the collision was severed. ## Operational Context and Flight Sequence The helicopter, based in Erstfeld/UR, was dispatched at 14:10 to rescue a glider pilot who had become entangled in trees on a steep slope at Alp Brändlen. The flight carried five individuals: the pilot, a doctor, a helicopter emergency medical services crew member (HCM), and two helicopter rescue specialists (RSH). The pilot selected an approach path perpendicular to the slope to minimize collision risks with other gliders and potential electrical wires. During a reconnaissance flight, the pilot and HCM assessed the situation using a moving terrain display. The pilot decided to land at an intermediate site approximately 500 meters south of the glider pilot's location to prepare for a winch rescue. During the final approach to this landing site, the doctor observed a cable, and the helicopter experienced an unnatural deceleration. The pilot saw a piece of the cable under the winch mirror and attempted to stop and move backward. A loud bang and a dull thud were heard, and the helicopter began to vibrate but remained controllable. The pilot then executed a normal landing in the ground effect. The glider pilot subsequently freed himself from the trees. ## Investigation Findings and Contributing Factors The Swiss accident investigation bureau (BFU) determined that the accident was caused by the helicopter colliding with a cable during the approach to a rural landing site. Contributing factors included the pilot's choice of a risky flight route and the fact that the cable, located in the area of the only usable helicopter landing site for this type of intervention, was not recorded in the obstacle database. The pilot and HCM had never been to Brändlen before this mission. The helicopter was equipped with a FLOICE collision warning device but did not have a cable cutter installed.