What happened
On September 12, 2009, a Z-1s43 LSi, registration OK-LSI, crashed in a wooded, hilly area near the settlement of Hlína, part of the Sobíňov municipality. The flight originated from Příbram, part of a formation of four aircraft—including a Z-142, C-182, and Z-50—all intending to fly via the Chotěboř waypoint to Skuteč under VFR conditions.
As the formation progressed, weather conditions began to deteriorate near Světlá nad Sázavou, with the cloud base dropping significantly. The crews of the other three aircraft agreed to divert to Zbraslavice to avoid the worsening weather. However, the crew of the OK-LSI did not acknowledge this agreement and likely continued toward the original destination. Other pilots in the formation reported hearing fragments of cockpit conversation via an accidentally unmuted radio, noting a high level of nervousness among the OK-LSI crew as they attempted to program their GPS.
The aircraft eventually entered an area with low visibility and a low cloud ceiling that did not meet VFR requirements. The aircraft struck the tops of trees with its left wing, causing the wing to separate, and impacted the ground at an angle of approximately 25-30 degrees. A post-crash fire destroyed the aircraft, resulting in two fatalities.
The investigation
The ÚZPLN investigation established that the aircraft's engine was functioning normally at the time of impact. While the investigation could not definitively prove a mechanical failure, it also found no evidence of technical malfunction. The investigation focused on the meteorological conditions, which were characterized by low ceilings and fog, and the crew's decision-making.
Medical examinations confirmed that both occupants died instantly due to polytrauma. Toxicological tests showed no presence of alcohol or prohibited drugs. The investigation also noted that the pilots were not trained for flight in IMC (Instrument Meteorological Conditions).
Findings
- The primary cause of the accident was flying into meteorological conditions unsuitable for VFR flight and the subsequent loss of spatial orientation.
- The crew failed to manage the aircraft effectively after encountering low cloud ceilings and low visibility.
- The decision to continue the flight despite the deteriorating weather and the lack of coordination with the other aircraft in the formation contributed to the accident.
- The aircraft struck trees, leading to structural failure and a subsequent impact and fire.