What happened
On the morning of September 5, 2020, a commercial hot air balloon flight departed from Estavayer-le-Lac, heading northeast toward Zofingen. The flight, operated by Take-Off Balloon AG, carried a pilot and seven passengers. The flight proceeded normally at altitudes between 4200 ft and 2200 ft AMSL until the pilot began descending toward the Wiggertal region.
Seeking a suitable landing site in the familiar area of Strengelbach, the pilot maneuvered the Ultramagic N-210, registration HB-QYM, to a very low altitude. While flying only a few meters above a forested area southwest of Zof andingen, the balloon experienced an unexpected drop in altitude. The pilot immediately activated both burners to increase heat and instructed passengers to crouch in the basket to avoid impact. Despite these efforts, the balloon collided with the treetops, resulting in light injuries to one person.
The investigation
Investigators examined the damage to the aircraft and the flight conditions at the time of the incident. The collision caused significant damage to the lower third of the balloon envelope, including torn fabric and severed load tapes. Additionally, one of the 28 load wires was found to have nearly all its strands broken. The basket, burners, and control lines remained undamaged. The investigation also reviewed the aircraft's maintenance history, noting the balloon had recently entered service following an airworthiness inspection in July 2020.
Findings
- The pilot attempted a challenging maneuver by flying at low altitude, approximately 20 km/h, just meters above tree canopy.
- The balloon experienced an unexpected loss of lift while passing over the forest.
- This loss of buoyancy may have been caused by the balloon entering a pool of cold air, common in valley floors, or by encountering dynamic turbulence generated by the treetops.
- The pilot was unable to compensate for the sudden loss of lift using the burners before the impact occurred.