What happened
On April 22, 2000, a Wörner K1000/3Stu gas balloon was participating in a long-distance competition flight near Norden-Norddeich, Germany. During an attempt to land north of the town, the pilot intended to fly over the rooftops of several houses to reach a landing field on the other side. However, while crossing the final row of buildings, the balloon encountered sudden sinking caused by lee vortices. Despite attempts to release ballast, the basket collided with a house roof.
The impact damaged external ballast bags, causing a loss of approximately 45 kg of sand. This sudden loss of weight caused the balloon to ascend to about 200 meters. Due to increasing winds and the proximity of high-voltage power lines, the pilot was unable to reach the original landing site and instead targeted a different field. To avoid the power lines and reach the available terrain, the pilot initiated a descent with a high sink rate. The balloon struck the ground with significant force, resulting in one person suffering a serious spinal injury.
The investigation
The BFU investigation examined the aircraft's technical condition, the pilot's experience, and the environmental conditions. The investigation found that the aircraft was properly registered and the pilot held a valid license. While the pilot was highly experienced in free balloons, his experience specifically with gas balloons was limited to only 54 flight hours.
Investigators also noted a discrepancy in wind data; while the pilot reported ground winds of 5–8 km/t, official meteorological stations recorded much higher speeds of 12–19 km/h. Furthermore, the investigation found that several sand ballast bags had been attached to the outside of the basket garland rather than inside the basket. This placement, requested by the pilot, made the bags vulnerable to damage during contact with obstacles.
Findings
- The primary cause of the accident was the uncontrolled hard landing necessitated by the loss of the planned landing site following the rooftop collision.
- The pilot's decision to land in a secondary field with a high sink rate was driven by the need to avoid power lines and the lack of remaining landing options near the coast.
- The pilot underestimated the physical impact and deceleration forces of the high-energy landing.
- The improper positioning of ballast bags outside the basket contributed to the significant loss of weight upon hitting the roof.
- A lack of recent experience in gas balloon operations contributed to the pilot's misjudgment of the landing conditions.