What happened
On the afternoon of January 27, 1978, an Enstrom F 280 C helicopter, registration HB-XET, was performing a return flight from Sedrun to Disentis. The pilot had previously flown to Sedrun to assist with a television news report and was returning to Disentantis to conduct passenger sightseeing flights.
During the approach to the landing site in Salaplauna, the aircraft deviated from the established flight path. While flying south of the designated safety boundary—marked by a highly visible high-voltage power line—the helicopter struck the cable of a material transport cableway. The impact severed the rear section of the fuselage and the tail rotor. The aircraft subsequently entered a forward pitch and a clockwise rotation before crashing into the forested terrain in the Vorderraterhein gorge. The impact caused a fire that destroyed the aircraft.
The investigation
The investigation, conducted in collaboration with the Graubünden Cantonal Police, examined the flight path, weather conditions, and the mechanical state of the aircraft. Investigators analyzed wreckage patterns, finding cable impact marks on the left skid and the underside of the tail section.
Evidence suggested that the pilot may have noticed the obstacle at the last moment and attempted an evasive maneuver by pitching up, but the collision was unavoidable. The investigation also noted that while the cableway was listed as a single obstacle in Swiss aeronautical charts, the cables themselves were not marked and were difficult to see against the snow-covered, shaded slope.
Findings
- The pilot was flying with valid authorization and was in good health.
- The Enstrom F 280 C was airworthy, and no pre-existing technical failures were identified.
- Weather conditions were favorable, with good visibility and light winds.
- The pilot was aware of the cableway's existence due to its presence in aeronautical charts.
- The pilot deviated from the prescribed approach sector for reasons that could not be determined.