What happened
On May 19, 1996, a commercial hot air balloon flight involving a Thunder & Colt 105A collided with overhead power lines near Königsdorf, Germany. The flight began at approximately 06:30 from Weyarn, with the pilot and four passengers traveling westward. After roughly one hour of flight, the crew sought a landing site near Dietramszell but found no suitable terrain. As ground winds increased and gusts became noticeable, the pilot decided to redirect the flight toward the Königsdorf airfield.
During the approach to the airfield, the crew encountered several small bodies of water and identified a 20 kV power line crossing their path. In an attempt to clear the three cables, the pilot attempted to gain altitude. However, the balloon failed to achieve sufficient climb rate in time. The basket struck the first conductor cable, causing a passenger to sustain a hand injury when their hand was caught between the basket and the wire. As the balloon rebounded, the floor of the basket subsequently slid over the remaining cables, triggering an electric arc. This arc caused two passengers to suffer electric shocks and resulted in severe damage to the balloon envelope, the basket, and a gas cylinder, which sustained localized welding damage. The collision also caused a power outage due to the tripped electrical line. The balloon continued its flight for approximately one kilometer before landing in an open field behind the Königually airfield.
The investigation
The BFU investigation focused on the flight conditions, the aircraft's technical state, and the pilot's decision-making process. Investigators confirmed that the pilot had consulted with flight weather services in Munich prior to departure and that the weather at the time of the accident was characterized by light easterly winds and clear conditions.
Technical examination of the Thunder & Colt 105A revealed that the four gas cylinders were nearly empty, meaning the burner could no longer operate at optimal performance. Witnesses noted that the pilot had been switching cylinders frequently during the final phase of the flight to maintain burner pressure. The investigation also analyzed the available landing sites, noting that suitable terrain was available prior to reaching the power lines that would have allowed for a safe landing with the remaining fuel.
Findings
- The primary cause of the accident was the incorrect estimation of clearance and distance when attempting to fly over the power lines.
- The pilot's decision-making was compromised by a lack of sufficient propane reserves, which resulted in diminished burner performance.
- Increasing wind gusts and turbulence contributed to the difficulty of maneuvering the balloon at low altitudes.
- The availability of alternative landing sites prior to the obstacle was not utilized, which would have prevented the balloon from entering a state of reduced controllability.