What happened
On July 26, 2012, an Ultramagic N180 hot air balloon, registration F-GOXA, operated by Alizé Montgolfière, was conducting a recreational flight carrying seven passengers. The flight departed from near Arleux around 05:00 UTC under clear skies. However, during the ascent, the pilot encountered rapidly developing dense fog. To maintain visibility, the pilot continued climbing to approximately 300 meters, flying above the fog layer for the duration of the flight.
After approximately 90 minutes of flight, the pilot decided to terminate the mission. Navigating via GPS and 1:500,000 scale aeronautical charts, the pilot selected a landing field near a departmental road in Vaulx-Vraucourt. As the balloon descended through the fog, the pilot spotted medium-voltage power lines. Although the pilot immediately activated the vent and cut the burners to descend, the balloon's envelope made contact with the lines. The impact caused a fire on the envelope, prompting the pilot to evacuate all seven passengers and use an onboard extinguisher to suppress the flames.
The investigation
The investigation focused on the meteorological conditions and the navigational tools used during the descent. While the pilot had consulted weather forecasts the previous day, these forecasts did not predict the fog. Satellite imagery confirmed that a fog bank had moved into northern France during the flight.
Investigators also examined the aeronautical charts used for the landing. The 1:500,000 scale aeronautical charts used by the pilot only indicate obstacles higher than 300 feet and specifically high-voltage lines (225 kV and above). Consequently, the medium-voltage lines involved in the collision were not marked on the pilot's primary aeronautical charts.
Findings
- The pilot did not update the meteorological information immediately before takeoff, failing to account for the developing fog.
- The pilot continued the flight despite the fog, which prevented a safe landing assessment.
- The collision with the power lines was not avoidable using the aeronautical charts provided, as the specific obstacle was not listed due to its voltage level.
- The use of more detailed topographic maps, such as IGN maps, might have identified the presence of the lines.