Investigation Summary
The flight departed Ljubljana–Brdo at 04:54 UTC under light wind conditions. As the balloon reached the Ljubljana Marshes, weather conditions deteriorated rapidly due to an approaching storm front. The balloon reached a peak altitude of 1,371 metres AMSL before beginning a rapid descent. During the final stages of the flight, wind speeds increased significantly, exceeding 40 km/h, and the wind direction shifted from north to north-west. The balloon experienced a high descent rate of 3.7 m/s. While the basket first struck the ground at 05:52:05 UTC at a speed of 43 km/h, ground speeds exceeding 50 km/h were measured from a height of 374 metres AGL, peaking at 63 km/h shortly before impact. The basket was dragged for 240 metres before becoming briefly airborne again. During the second impact 43 seconds later, the basket struck treetops, which severed gas pipes. Because the pilot had not closed the shut-off valves on the propane tanks during the emergency landing sequence, the leaking gas ignited immediately upon contact with the burner or other ignition sources in the basket.
Final Conclusions
The Slovenian Aircraft Accident Investigation Commission concluded that the direct cause was the improper technique used in operating the LBL 600C balloon during the landing phase. Specifically, the pilot failed to close the gas tank shut-off valves, which directly led to the post-crash fire. Indirect causes included insufficient meteorological planning and a failure to account for the deteriorating weather conditions at the time of the flight. The investigation was documented in the Final Report FR_S5_OLO_23082012-ANG, published approximately two years after the accident.
Video Analysis
No video analysis linked for this case file yet.
Systems & Failure Modes
Gas Equipment
The propane fuel system included tanks with shut-off valves and piping leading to the burners. These pipes were damaged during the tree collision, allowing gas to escape because the valves remained open.
LBL 600C Basket
A large-capacity basket designed for 32 occupants, measuring 5.20m by 1.70m, which provided significant surface area for wind to act upon during the dragging phase.
Interesting Facts
- 01The Lindstrand LBL 600C was the largest serially manufactured hot air balloon in the world at the time.
- 02The manufacturer serial number (MSN) for this balloon was 1252.
- 03The basket was 5.20 meters long and divided into four compartments.
- 04Four victims were killed instantly and charred beyond recognition; two others died later from their injuries.
- 05The pilot was later exonerated in a 2018 district court trial based on a foreign expert's opinion, despite the official accident report findings.
- 06Commercial hot air balloon flights were banned in Slovenia for one year following the accident.
Safety Actions & Advisories
Temporary Flight Ban
The Slovene Civil Aviation Agency implemented a temporary ban on all commercial hot air balloon flights starting August 27, 2012.
Regulatory Reform
New, stricter rules for hot air balloon operations were developed and accepted, with licensing resuming in August 2013.
Known Controversies & Unanswered Questions
Judicial Exoneration vs. Investigative Findings
Reference ↗While the official accident report cited pilot error and improper technique as the cause, a Slovenian district court exonerated the pilot in 2018 based on a foreign expert's testimony that contradicted the commission's findings.