What happened
On May 9, 2001, a Thunder & Colt 210A hot air balloon, registration HB-BEQ, was conducting a commercial passenger flight near Jaun, Switzerland. After flying through the Prealps, the pilot decided to terminate the flight in the Jogne Valley. During the approach to a landing site near a residential area, the pilot attempted to adjust altitude to avoid a forested area and a steep slope.
While maneuvering, the basket of the balloon struck a 17,000-volt medium-voltage power line. The collision triggered a violent electrical arc. The pilot was thrown backward by the force of the discharge and sustained severe second and third-degree burns to his arm, neck, and leg. Following the impact, the balloon remained momentarily entangled in the wires before drifting away. Due to the pilot's incapacitation, a passenger took control of the balloon, following radio instructions from the ground crew and another balloon crew to perform an emergency landing near a ski lift.
The investigation
The investigation examined the flight path, the electrical discharge mechanism, and the environmental conditions. Investigators established that the pilot was experienced but was likely hindered by the sun's position during the approach. The investigation also analyzed the electrical path, determining that the current traveled through the metal components of the basket and propane cylinders, creating multiple points of contact with the pilot's body.
Findings
- The primary cause of the accident was the collision between the balloon basket and a 17,000-volt power line while maneuvering in a confined area.
- The pilot likely failed to detect the line in time because the sunlight was blinding him, causing the wires to blend into the landscape.
- The pilot's physical injuries were caused by a potential difference established between the metal fittings of the propane cylinders and the basket structure, which channeled the current through his body.
- The choice of landing site was influenced by the difficult topography of the narrow valley and the need to find suitable terrain before thermal conditions changed.