What happened
On September 4, 2011, a hot air balloon, registration OK-4ass, was conducting a sightseeing flight with three passengers. The flight originated from Radešín, heading toward Žďár nad Sázavou and over the forested Žďárské vrchy region. As the flight progressed, wind speeds increased, leading to the development of turbulence.
In response to the deteriorating weather, the pilot decided to perform an immediate landing at a nearby suitable location, a large meadow approximately 0.6 km southeast of Slavětín. Prior to the maneuver, the pilot instructed the passengers to secure all loose items, such as cameras, and to adopt a crouched position while holding onto the basket handles.
During the final approach, the balloon encountered unexpected turbulence while passing the edge of a forested area. This caused a sudden loss of altitude, resulting in the bottom of the basket striking the ground. The impact caused the basket to tip onto its side and slide approximately 20 to 25 meters along the ground. The balloon then bounced and traveled an additional 50 meters before coming to a final rest. While the pilot remained uninjured, the three passengers sustained serious injuries to their lower limbs and were transported to hospitals in Havlíčkův Brod and Nové Město na Moravě.
The investigation
The ÚZPLN investigation established that the pilot was fully qualified, held a valid medical certificate, and was competent for the flight. The aircraft, a BB34Z manufactured by Balóny Kubíček, was found to be in good technical condition with no previous defects noted in its maintenance history.
Investigators examined the meteorological conditions and determined that while the initial forecast was suitable for flight, the wind intensified unexpectedly over the forested terrain, creating mechanical turbulence. The investigation also confirmed that the pilot had taken appropriate safety precautions by instructing the passengers on landing procedures and positioning them correctly within the basket prior to the impact.