What happened
On October 13, 1998, at approximately 16:55 local time, an Alouette III SE3160, registration HB-XDE, crashed into a rock formation in the mountains near Verbania, Italy. The aircraft, owned by the Swiss Federal Office of Civil Aviation, was performing a ferry flight from Bern-Belp Airport to Locarno-Magadino Airport.
During the return leg of the flight, the pilot was navigating through a mountainous zone. Shortly before the impact, a group of technical workers near the Piano dei Camosci area observed the helicopter flying in steady, horizontal flight at an altitude of approximately 3,000 meters. However, the aircraft subsequently struck a rock outcrop at an altitude of roughly 2,970 meters, approximately 7/50 km northwest of the Claudio e Bruno alpine hut. The impact caused the total destruction of the helicopter and resulted in one fatality.
The investigation
The investigation, conducted by a joint commission of Italian and Swiss authorities, involved a detailed examination of the wreckage at a hangar in Locarno. Investigators analyzed the state of the tail boom, main rotor, and engine. While the tail drive shaft showed evidence of a torsional break, this was attributed to the inertia of the tail rotor after the shaft had already been blocked by the impact.
Technical analysis of the instruments revealed that the airspeed indicator was frozen at 113 km/h at the moment of impact. Microscopic examination of the warning light panel showed that several lamps, including those for fuel filter, generator, and oil pressure, were not illuminated at the time of the crash, indicating no active warnings were present. The investigation also included a reconstruction flight to assess visibility and terrain recognition at the time of the accident.
Findings
- The pilot was fully qualified and held all necessary flight authorizations.
- The meteorological conditions, while involving wind gusts, were suitable for the intended flight.
- The Alouette III SE3160 was airworthy and had been maintained according to regulations.
- No mechanical failures or operational malfunctions were identified as direct causes of the crash.
- Medical and pathological examinations of the pilot revealed no signs of a heart attack or toxicological issues, though evidence of long-term heart tissue degeneration was noted.
- The investigation concluded that the accident was likely caused by a sudden and temporary bout of nausea experienced by the pilot, leading to a loss of control and subsequent impact with the terrain.