What happened
On 6 August 2013, a Cameron Z-120 hot-air balloon, registration HB-QOW, was conducting a passenger flight near Montbovon, Switzerland. The flight, operated by Gstaad Fly S.à r.l., began in Château-d'Oex. During the flight, a passenger's request to cease climbing forced the pilot to alter the planned trajectory, descending into a valley toward the La Comba d'Avau area.
As the balloon approached the landing site, it encountered a local wind known as the Ruchio. While attempting to maintain altitude, the balloon's basket descended below the level of high-voltage power lines crossing the valley. At 08:38, the aircraft collided with the electrical conductors. The impact caused electric arcs, severed nine of the twelve cables connecting the envelope to the basket, and led to a rapid deflation of the envelope. The basket fell approximately 40 meters, landing violently in a garden. The accident resulted in one fatality and three serious injuries among the passengers, while the pilot sustained serious injuries.
The investigation
SUST examined the flight history, technical components, and environmental conditions. The investigation reviewed statements from the pilot, passengers, and local witnesses, as well as photographic and video evidence. Investigators reconstructed the flight profile, noting that while the balloon was initially at a height sufficient to clear the obstacle, its altitude dropped significantly during the final approach. The investigation also looked into the technical state of the burners and gas cylinders, as well as the impact of local meteorological conditions on the flight path.