What happened
On September 28, 2016, at approximately 13:59 UTC, a VSO-10 glider, registration OK-0581, crashed into a wooded area near the village of Zbyslavec. The pilot was performing ridge soaring maneuvers over a slope located approximately 500 meters west of the village.
Prior to the accident, the pilot had been conducting glider towing operations at Podhořany Airport (LKPN) and had completed several successful flights in the area. While flying at an altitude of approximately 50 to 100 meters AGL, the pilot initiated a right-hand turn. During the maneuver, the aircraft encountered severe rotor turbulence on the lee side of the ridge. This turbulence caused a sudden and rapid loss of both airspeed and altitude. The pilot attempted to return to the windward side of the slope, but the loss of energy was too great to maintain flight. The aircraft struck trees, with the cockpit area hitting a large tree trunk, causing the canopy to shatter before the glider impacted the ground.
The investigation
The ÚZPLN investigation examined the aircraft, the meteorological conditions, and the pilot's actions. The investigation confirmed that the VSO-10 was airworthy and had undergone its most recent 100-hour inspection in July 2016. The pilot held a valid glider rating and was physically and mentally fit for the flight.
Meteorological data from the Czech Hydrometeorological Institute indicated that while visibility was excellent, there were surface winds between 13–18 knots with gusts up to 25 knots. These winds, blowing perpendicular to the ridge, were a significant factor in creating mechanical turbulence. The investigation also reviewed the flight path and the pilot's experience in the local terrain.