What happened
On December 28, 2016, a paraglider pilot launched from the Güggel takeoff site near Oberdiessbach, Switzerland, at approximately 14:31. The flight was part of a planned second excursion following a successful first flight. Shortly after takeoff, while flying at an altitude of roughly 50 meters above the ground near the Glasholz farm, the pilot's Gradient Golden4 22 wing suddenly became unstable and experienced a frontal collapse. The wing failed to reinflate, leading to a rapid descent and a hard impact on a steep meadow. The pilot sustained serious injuries to her back and hand.
At the same time, an EC 120 B helicopter, registration HB-ZFM, was operating in the vicinity. The helicopter pilot had been performing private sightseeing flights and was maneuvering near Barschwand, following power lines. The helicopter flew past the paraglider at a lateral distance of approximately 100 meters. While the helicopter pilot reported not seeing the paraglider, the accompanying paraglider pilot observed the helicopter and communicated its position to the flying pilot via radio.
The investigation
SUST examined the flight paths of both aircraft, utilizing radar data for the helicopter and GPS logs from the paraglider's logger. The investigation looked into the meteorological conditions, which were sunny with light winds and a stable temperature inversion. Investigators also reviewed the technical state of both aircraft, noting that the paraglider's brake lines were slightly shorter than manufacturer specifications, though no mechanical failure was identified as a primary cause. The investigation also assessed the visibility and contrast of the aircraft, noting the paraglider's dark green and black coloring, which likely made it difficult for the helicopter pilot to spot against the terrain.