What happened
On July 19, 1997, at approximately 21:05, a hot air balloon accident occurred near the Pori airport in Finland. The aircraft, a Cameron A140 with registration OH-IDA, was performing a promotional flight as part of the Pori-Jazz event.
During the landing sequence on a grassy area near the runway intersection, the basket struck the ground unevenly. The impact caused the basket to tilt and subsequently tip onto its side. This movement caused the burner frame to strike the ground, which in turn caused one of the burner's main valves to partially open. The escaping gas ignited from the pilot flames, sending fire toward the basket.
The resulting fire caused three passengers to sustain serious burns, with two suffering third-degree injuries. The pilot sustained minor burns to the face and hands. The basket and the balloon's envelope sustained damage, and a small area of grass was burned during the incident.
The investigation
The investigation examined the mechanical integrity of the burner assembly and the basket structure. Investigators found that the basket and burner mounting were highly flexible; the burner frame was capable of hitting the ground even without significant load, and the multi-link burner assembly lacked mechanical stops to prevent it from pivoting toward the basket.
Additionally, the investigation reviewed the emergency response. It was noted that the emergency dispatch provided an outdated access instruction ("eastern gate") that did not align with the current airport layout. Furthermore, the medical crews were using outdated airport maps, which caused a delay of approximately two minutes as they searched for the correct entry point.
Findings
- The primary cause of the accident was the opening of a burner main valve due to the basket tipping during landing, which allowed gas to ignite.
- The burner assembly lacked mechanical limiters, allowing the burners to rotate toward the passengers.
- The basket structure was sufficiently flexible that the burner frame made contact with the ground during the landing impact.
- The pilot flames were still active during the landing, contrary to the recommendation in the flight manual to extinguish them before touchdown.
- Incomplete maintenance tasks from a previous inspection had not been verified or cleared.
- Emergency response was hindered by outdated navigational information and gate instructions provided to the medical crews.