What happened
On July 2, 2011, a Cameron A250 hot air balloon, registered CS-BAS, was conducting a sightseeing flight near Lacalm, France. The flight, intended to carry 14 passengers, had been rescheduled from a previous date due to poor weather. To ensure sufficient fuel for the flight path near a lake, the pilot had carried an extra gas cylinder, which reduced the allowable passenger weight.
During the flight, the pilot observed that the wind strength was significantly higher than anticipated. To avoid drifting over a nearby lake, the pilot decided to perform a precautionary landing. The pilot instructed passengers to crouch and hold onto handles to mitigate the risk of being ejected. The pilot aimed the basket at the treetops to use the vegetation to slow the descent. However, the basket struck the trees, causing the envelope to collapse and the basket to strike the ground violently. The basket bounced and overturned during a second impact, sliding approximately 30 meters. During the incident, three passengers were ejected from the basket, and the pilot's arm became trapped under the basket during the slide. The accident resulted in one pilot and seven passengers injured, with the basket sustaining minor damage.
The investigation
The investigation focused on the meteorological data used for flight planning and the aircraft's airworthiness. While the pilot used a generalist weather website, investigators found that the aeronautical forecasts available at the time indicated a significant increase in wind speed at altitude that the pilot had not anticipated. Furthermore, the investigation revealed discrepancies regarding the aircraft's documentation; while the envelope was marked as a Cameron A250, Portuguese authorities identified the registration CS-BAS as a Cameron N90 with an expired certificate of airworthiness.
Investigators also examined the safety procedures for passengers. It was determined that the cramped space within the basket prevented all passengers from effectively crouching as instructed. One passenger was physically unable to crouch, which contributed to their ejection during the impact.
Findings
- The primary cause of the accident was the pilot's decision to proceed with the flight despite aeronautical forecasts predicting strengthening winds.
- The use of a generalist weather website provided insufficient and imprecise information, preventing the pilot from anticipating the actual wind conditions encountered during flight.
- The pilot's lack of familiarity with the local terrain prevented the recognition of potential low-level rotors caused by the nearby landscape.
- Safety instructions regarding crouching were not effectively implemented due to the limited space in the basket and the physical limitations of certain passengers.