What happened
On October 30, 2007, during a tethered flight event in Zeltweg, Austria, a Cameron A-140 hot air balloon experienced an uncontrolled ascent. The flight was part of a series of tethered launches organized by a local club. During the flight, the pilot had ascended to approximately 25 meters above ground level.
After a controlled descent and landing, the pilot instructed passengers to disembark in a specific order, starting with the children. While the final child was in the process of exiting the basket, two adult passengers jumped out of the basket simultaneously. This sudden loss of weight caused the balloon to surge upward rapidly. Because the basket had not been fully secured to the ground, the ascent could not be prevented by the ground crew.
During this sudden movement, one of the tether lines—which had not been tensioned following the landing—wrapped around the lower leg of a child who had already exited the basket. The child was lifted approximately 10 meters into the air, resulting in severe injuries to the left lower leg. The pilot was able to mitigate the ascent by immediately using the vent valve, and ground crew eventually assisted the child.
The investigation
The SUB investigation examined the flight sequence, the aircraft's technical condition, and the loading configuration. The investigation reconstructed the events using eyewitness accounts and passenger statements. The inquiry also reviewed the pilot's qualifications, the aircraft's maintenance records, and the weight and balance of the balloon at the time of the incident.
Findings
- The balloon was properly registered, insured, and maintained with a valid airworthiness certificate.
- The pilot held all necessary valid licenses and qualifications for the operation.
- The aircraft's weight and center of gravity were within permissible limits, although the maximum passenger capacity was exceeded by two people.
- Meteorological conditions were favorable and were not a contributing factor to the accident.
- The primary cause of the uncontrolled ascent was the unexpected behavior of the passengers, specifically the simultaneous exit of two adults which caused a sudden loss of mass.
- One of the tether lines was not under tension at the time of the incident, allowing it to loop around the child's leg.