What happened
On August 8, 2022, during the preparation for a commercial flight near Beelitz, Germany, a Theo Schroeder fire balloons G 50/24 hot air balloon experienced a sudden, unexpected ascent. The balloon was in the process of being inflated with cold air and heated when an exceptionally strong thermal bubble detached nearby. This sudden upward force caused the balloon to lift abruptly while still connected to its ground support equipment.
The balloon's tether, which was attached to a VW Bus and trailer via a safety line, was pulled with such force that the support vehicle was yanked from its stationary position. The vehicle was lifted at a 45-degree angle and dragged approximately 30 meters into nearby bushes. During this chaotic movement, a passenger standing near the vehicle was struck by the moving car, resulting in one fatality due to polytrauma.
Following the loss of the tether, the balloon continued to ascend rapidly. The pilot reported that the intense upward movement caused significant deformation and twisting of the envelope, which prevented the parachute system from closing properly. The pilot was forced to shut off all gas valves and prepare for a high-rate descent, eventually resulting in a hard impact with the ground.
The investigation
The BFU investigation focused on the meteorological conditions and the mechanical failure of the tethering components. Investigators examined weather data from the German Meteorological Service (DWD), specifically analyzing the ICON-D2 model forecasts and the pilot's pre-flight briefings. The investigation also reviewed video evidence captured by witnesses, which documented the inflation process and the sequence of the accident.
Technical examination of the aircraft revealed that the four steel cables of the launch aid attachment had snapped, and a carabiner in the safety device had been deformed. The investigation also confirmed that the support vehicle's parking brake was engaged and functional, but the vertical lift force of the balloon was sufficient to overcome the friction of the tires on the grass.
Findings
- The primary cause of the accident was the abrupt detachment of a strong thermal bubble in the immediate vicinity of the launch site.
- The intensity of the wind event was likely amplified by a convective wind convergence occurring near the launch site.
- The pilot began the inflation process while moderate to strong thermic activity was still active, rather than waiting for the end of the thermal period.
- The sudden upward force was great enough to lift the 3-ton support vehicle, rendering the parking brake ineffective against the vertical momentum.