What happened
On January 22, 1998, at 14:40, an amateur-built hot air balloon, registration I-PAAM, was participating in an aerial raid over the Drôme department. While flying above a cloud layer, the pilot received a radio report indicating that wind gusts in the region had reached 30 knots. In response, the pilot decided to descend through a gap in the clouds to end the flight.
As the balloon descended, the pilot identified a potential landing field, but significant wind drift forced a change in the approach toward a different location. During the final approach, a powerful downdraft caused half of the balloon's envelope to deflate. This sudden loss of lift, combined with high-speed horizontal wind movement, led to an uncontrollable descent. During the impact, the envelope became entangled with an electrical line, which snapped under the tension. The balloon continued its trajectory, striking a wall and the roof of a house before finally hitting the ground. The pilot sustained one injury.
The investigation
The investigation focused on the meteorological conditions and the pilot's decision-making process. At the time of the accident, ground winds were reported between 15 and 20 knots, with gusts reaching 35 to 45 knots. The area was experiencing strong to very strong turbulence and rotors on the leeward side of local terrain. The investigation also noted that the pilot had been briefed prior to the flight regarding the Mistral winds in the Rhône Valley, which were expected to reach 19 knots with 30-knot gusts, as well as low cloud cover.
Findings
- The primary cause of the accident was the insufficient consideration of weather forecasts prior to the flight.
- A sudden downdraft caused a partial deflation of the balloon's envelope, leading to a loss of flight control.
- High wind speeds and turbulence contributed to the inability to maintain a stable approach to the landing site.