What happened
On June 16, 1999, a Schroeder Fire Balloons G 30/24 hot air balloon was conducting a flight near Ibbenbüren, Germany. The flight, which included the pilot and three passengers, proceeded normally until the aircraft approached a 110 kV high-voltage transmission line. Witnesses observed the balloon descending to an altitude of approximately 15 to 40 meters as it approached the infrastructure.
As the balloon attempted to ascend to clear the lines, the basket became snagged on the system's earth wire at the level of the basket's upper rim. The pilot attempted to free the aircraft by increasing lift to break the wire, but the tension was too great. During these maneuvers, the basket drifted into contact with the live phase conductors of the southern system. This contact triggered a 46-second short circuit characterized by intense arcing and heavy sparking.
The resulting electrical discharge ignited the basket. The intense heat caused propane to escape from the fuel cylinders via their safety valves, which further accelerated the fire. As the basket burned, the structural integrity of the floor and walls failed, causing passengers, equipment, and gas cylinders to fall into a nearby retention basin. Eventually, the electrical arc welded the earth wire, causing it to break and fall, which triggered a secondary phase-to-phase short circuit and a local power outage.
The investigation
The BFU investigation examined the flight path, the mechanical state of the Schroeder Fire Balloons G 30/24, and the meteorological conditions. Investigators analyzed the wreckage, including the recovered GPS unit, and reviewed witness testimonies regarding the balloon's approach to the power lines. The investigation also included a forensic examination of the basket's structural failure and the impact of the electrical discharge on the fuel system.
Findings
- The pilot was highly experienced, with over 1,500 flight hours, and was fully qualified for the flight.
- Weather conditions were ideal, with light winds and high visibility.
- The aircraft was in airworthy condition with no mechanical defects found.
- The basket became physically entangled with the earth wire of the transmission line.
- The pilot flew the balloon at an undeservedly low altitude near the high-voltage lines without an apparent reason.
- The subsequent electrical short circuit caused intense heat and ignited escaping propane, leading to the rapid destruction of the basket and the deaths of all 4 occupants.