What happened
On August 26, 2001, at approximately 06:35 UTC, a Balloons Cameron A 140 hot air balloon, registration F-GKER, was conducting a local pleasure flight near Verrens-Arvey, France. The flight, which included the pilot and five passengers, departed from the Albertville ice rink.
After approximately twenty minutes of flight, the balloon approached a known landing area near the intersection of roads CD 2 and CD 64b at a very low altitude. As the balloon moved northwest, the basket struck a medium-voltage power line situated roughly eight meters above the ground. The impact immediately ignited the basket and the balloon envelope. The heat from the fire, combined with a last-second attempt by the pilot to increase altitude using the burner, caused the balloon to rise approximately thirty meters. During this ascent, two passengers fell from the basket.
As the balloon continued to drift southwest, the fire spread to the envelope. Approximately 1.5 kilometers later, an explosion occurred as gas cylinders were compromised, causing two more passengers and the gas cylinders to fall from the basket. The remaining occupants, including the pilot, were in the basket when it finally landed in a field, where the wreckage was completely destroyed by fire.
The investigation
The investigation focused on the wreckage distributed across three distinct sites. At the first site, investigators found evidence of severed electrical wires and two victims. The second site contained the remains of two other occupants, parts of the basket, and the four aluminum gas cylinders. One cylinder showed evidence of an electrical arc, while another had been ruptured from the inside out. The third site contained the final two occupants and the remains of the scorched envelope and basket floor.
Investigators examined the Cameron MK4S burners and found no mechanical anomalies. Witnesses, including a ground crew member following the flight by car, noted that the pilot attempted to use the burner to gain altitude just before the collision, a maneuver that proved ineffective due to the balloon's inertia.
Findings
- The primary cause of the accident was the late detection of the power line obstacle.
- Several factors contributed to the failure to identify the wires, including the pilot'1s focus on landing maneuvers, the presence of trees obscuring the utility poles, and the fact that the balloon was already traveling parallel to another power line, making the second line harder to perceive.
- The pilot's decision to use the burner to avoid the obstacle rather than the vent valve (parachute valve) prevented a controlled descent. While the vent valve would have caused a harder landing, it would have lowered the altitude of the basket and likely prevented the collision with the wires.
- The collision caused an electrical arc that punctured a gas cylinder, leading to the subsequent fire and explosion.