What happened
On August 20, 2013, a Cameron O 120 hot air balloon, registration F-GJTT, operated by Air Libre Montgolfière, was performing a flight near Thézac, France. After approximately one hour of flight, the pilot decided to land in a nearby field. While flying at an altitude of roughly ten meters, the pilot aborted the initial approach to seek a more suitable landing area.
While traversing a cornfield at a very low altitude, the pilot spotted an electrical power line. Realizing a collision was unavoidable, the pilot immediately activated the safety valve to initiate an emergency descent, following manufacturer recommendations to ensure the envelope—rather than the basket—made contact with the wires. However, the momentum of the balloon caused the suspension cables to strike the lines, triggering an electric arc. The impact severed three strands of the medium-voltage line and caused the balloon to come to a halt in the field.
The investigation
The investigation focused on the structural integrity of the aircraft and the visibility of the obstacle. Examination of the wreckage revealed that four suspension cables connecting the basket to the envelope had been subjected to extreme temperatures, causing them to rupture. The scoop, used to direct hot air into the envelope, was also torn and showed burn marks.
Investigators found that the three-strand power line was positioned approximately twelve meters above the ground. The supporting poles were partially obscured by vegetation and nearby buildings. Because the three wires were aligned on the same horizontal plane, the pilot could only perceive a single wire from the low flight altitude. The pilot, an experienced aviator with approximately 700 flight hours, noted that the clear blue sky made the wires difficult to detect and that the power lines were not indicated on aeronautical charts for that area.