Swiss Helicopter Collision with Unregistered Cable in Uri (HB-ZDX)

Incident Overview and Aircraft Details On August 8, 2018, at approximately 07:55 local time, an AS 350 B3 helicopter registered as HB-ZDX was involved in a collision with an obstacle during a commercial visual flight rules (VFR) operation. The aircraft was owned and operated by Swiss Helicopter AG, based in Chur. The pilot, a Swiss national born in 1961, held a commercial pilot license for helicopters issued by the Federal Office of Civil Aviation (BAZL) under EASA regulations. He had a total of 13,505 flight hours, including 6,599 hours on the accident aircraft type. ## Flight Operations and Accident Sequence The helicopter departed from Erstfeld (LSXE) at 07:44 local time for a transport mission to Schwand in the canton of Uri. The pilot had been asked to perform the flights the previous evening because a colleague lacked sufficient experience. A detailed briefing was conducted using a printed map excerpt and an electronic moving terrain device, which included obstacles under 25 meters above ground. During the approach to the drop-off site, located about 80 meters northeast of the Schwand farm, the flight helper B opened the left sliding door to observe obstacles. The pilot confirmed via intercom that the landing area was clear after consulting the electronic map. Just before touchdown, the pilot noticed a cable on the right side at the height of the front door frame. The flight helper, monitoring the left side, did not see it. The pilot called out “cable” as the main rotor blades struck the obstacle, causing strong vibrations. ## Emergency Response and Damage The pilot determined that his only chance of survival was to land the helicopter directly beneath him. He pushed the collective pitch lever down with full force and successfully landed the aircraft. Both the pilot and the flight helper remained uninjured. The pilot secured the collective and attempted to shut down the engine according to the Rotorcraft Flight Manual, but the helicopter was unstable due to ground resonance and repeatedly bounced. The pilot opened his right door to create an escape route and exited safely after the main rotor stopped. The collision and subsequent vibrations damaged the main rotor blades, rotor head, landing gear, cabin, and engine intermediate flange. The aircraft was heavily damaged, with no third-party damage reported. ## Obstacle Reporting and Regulatory Context The involved hay cable was not registered and therefore not included in the Swiss aviation obstacle database. The helicopter was equipped with a cable cutter system but did not have a collision warning device installed at the time of the accident. In Switzerland, aviation obstacles have been required to be reported since 1973 under the Ordinance on Air Navigation Infrastructure (VIL). Cantons are responsible for designating authorities to receive and forward obstacle reports to the BAZL. The BAZL database includes reported obstacles in non-built-up areas that are 25 meters or more above ground. Obstacles below this threshold are generally not systematically recorded, as the BAZL considers the data volume unmanageable and the safety benefit insufficient. The Web-GIS Obstacle Map (WeGOM) is updated twice weekly with published obstacles. While ICAO guidelines require recording obstacles outside aerodromes only above 100 meters, Swiss national regulations use a 25-meter threshold. Some cantons, such as Ticino and Uri, maintain separate lists for material cableways, and certain cantonal power companies provide digital line data to the BAZL. The Swiss Air-Rescue (REGA) has also independently sought to systematically record obstacles under 25 meters above ground.