What happened
On November 3, 2019, an ASW-19 glider, registration OK-4481, was performing a wave flight near the Jeseníky Mountains. The pilot had taken off from Mikulovice airport using a tow plane, intending to utilize mountain wave lift. After approximately two hours of flight, the aircraft reached an altitude of 6,759 m MSL.
During the flight, the aircraft entered a series of maneuvers. At approximately 12:34 UTC, the glider was performing turns at high altitude. GPS data indicated a significant and sudden increase in airspeed, with recorded speeds reaching as high as 402 km/h. This exceeded the aircraft's maximum permissible speed (VNE) for that altitude, which is 200 km/h. Following this speed excursion, the glider entered a steep, high-speed spiral dive. The structural integrity of the wings failed, with both wing halves separating from the fuselage. The fuselage and tail section struck the ground near the village of Ludvíkov, resulting in one fatality.
The investigation
The ÚZPLN investigation examined the aircraft wreckage, GPS/OGN flight data, and the pilot's medical and professional background. Investigators analyzed the flight trajectory, which showed erratic position changes and extreme speed fluctuations during the critical phase. The investigation also looked into the pilot's physiological state, specifically considering the risks of hypoxia and fatigue, as the pilot had been flying at altitudes exceeding 6,000 m MSL where supplemental oxygen is mandatory.
Findings
- The primary cause of the accident was a loss of control over the glider, which led to a steep, descending spiral.
- The aircraft's wings suffered a structural failure due to critical loading, likely caused by exceeding the maximum permissible speed (VNE) by approximately 50%.
- The pilot's exact state of control cannot be definitively determined, but the possibility of hypoxia or fatigue cannot be ruled out, as the pilot was flying at high altitudes and may not have had sufficient rest prior to the flight.
- The aircraft was airworthy and properly maintained prior to the flight.
- Meteorological conditions were suitable for VFR flight, though the aircraft was likely flying within cloud layers during the critical phase.