What happened
On August 21, 2000, a commercial hot air balloon flight involving six passengers encountered rapidly increasing wind speeds near Weibhausen. After departing at 07:42, the pilot ascended to an altitude of over 1,000 meters, where the balloon reached ground speeds exceeding 20 knots. As weather conditions deteriorated, the pilot sought a landing site to avoid worsening conditions.
During the descent, the balloon passed over a forested area at low altitude. While attempting to land behind the tree line, the basket made its first hard impact with the ground approximately 150 meters past the edge of the woods, traveling at a forward speed of 12–15 knots and a descent rate of 3–4 m/s. The impact caused the basket to bounce, leading to a second and third hard impact before the balloon finally came to a halt. The accident resulted in two serious injuries and one minor injury among the passengers.
The investigation
The BFU investigation examined the weather data, the pilot's preparations, and the technical aspects of the flight. Investigators found that while the pilot had obtained a weather report via fax at 04:04, this information was outdated. A more recent warning issued at 06:30 by the German Meteorological Service (DWD) regarding an approaching cold front and thunderstorm activity had not been reviewed prior to takeoff.
At the launch site, conditions appeared calm due to a surface inversion, and no wind measurement tools, such as a test balloon, were used. Consequently, the pilot was unaware that significant winds were present just above the treetops. Additionally, the investigation noted that the passengers had not received a full safety briefing or the required passenger information leaflets prior to the flight, contrary to the operator's manual.
Findings
- The flight was initiated under unsuitable wind conditions.
- The pilot failed to update the weather information after the initial 04:04 report, missing critical warnings about a developing convergence line and high winds.
- The descent into the lee of the forest caused the balloon to encounter turbulence, which significantly increased the descent rate.
- The pilot did not activate the rapid deflation system of the envelope during the landing sequence, making the multiple hard impacts unavoidable.
- The forward speed and descent rate could not be sufficiently reduced before the initial ground contact.