What happened
On 2 September 2009, a Thunder AX7-77 hot air balloon, registration G-BSZH, was performing a private flight in Bilsdale, North Yorkshire. As the pilot was approaching a landing in a sheltered field, the aircraft encountered power lines crossing the landing area. While the pilot initially believed the balloon was clear of the lines, the aircraft briefly reversed direction approximately 20 feet above the ground.
During this maneuver, the suspension cables made contact with the power lines. The resulting friction and tension caused the connecting wires to sever, causing the basket to detach from the envelope and fall roughly 15 feet to the ground. The impact resulted in two minor injuries to passengers, while the pilot remained unhurt.
The investigation
The investigation examined the flight path and the environmental conditions at the time of the accident. The pilot noted that the landing site was free of livestock but was intersected by overhead power lines. The investigation established that the balloon had enough fuel to reach more open ground, but a sudden change in direction brought the aircraft into contact with the wires. The pilot suggested that the unexpected reversal of the balloon's direction was likely due to local airflow changes caused by a ridge the aircraft had recently passed over.
Findings
- The primary cause of the accident was the contact between the suspension cables and the power lines, which led to the structural failure of the connecting wires.
- Localized wind patterns, specifically the reversal of airflow in the lee of a nearby ridge, contributed to the unexpected movement of the balloon toward the wires.