Accident Sequence
On 19 July 2019, at 13:49 UTC, a glider L-13 Blaník (registration OK-4716) sustained damage during a training flight at Mladá Boleslav Airport (LKMB). The flight was part of a student pilot's training under the supervision of a flight instructor, focusing on emergency procedures following a winch launch. The winch operator had been instructed to perform two practice releases for the "land ahead" maneuver. The first release occurred at approximately 30 meters above ground, and the instructor demonstrated the correct response. On the second launch, the winch released at about 15 meters. The student pilot pushed the control column forward to gain speed and released the tow rope. However, the glider sank and struck the ground hard. The crew was uninjured.
Aircraft and Crew
The glider, an L-13 Blaník manufactured by Let n.p. Kunovice in 1974 (serial number 026233), had a total flight time of 3,820 hours and 45 minutes, with 6 hours and 26 minutes since its last A-check. It was not equipped with a flight recorder. The student pilot, aged 54, had 95 flights totaling 11 hours and 18 minutes, including 11 winch launches. The instructor, aged 49, held a valid glider pilot license with an FI(S) rating and had 1,845 hours and 49 minutes on gliders, with 879 hours and 24 minutes as an instructor. The winch operator, aged 20, had about 500 winch launches and a valid qualification.
Meteorological Conditions
According to the Czech Hydrometeorological Institute, the weather was influenced by an occluded front moving from west to east. The atmosphere was unstable with convective cloud development, including cumulus, stratocumulus, and isolated towering cumulus (5–7/8 coverage) with bases around 1,300–1,500 meters. Rain was falling from the clouds. Visibility exceeded 10 km, and the air temperature was 20–23 °C. Wind at nearby stations was from 240–270° at 5–8 knots, gusting to 12–18 knots. At 09:30 UTC, the local information station recorded QNH 1014, 8/8 cloud at 5,000 feet, and wind 240° at 5 knots.
Damage
The impact occurred on Runway 34, which had a dry, hard surface. The glider slid about 42 meters before stopping. Damage included deformation of the lower forward and aft fuselage skin, collapsed floor sections, cracked landing gear attachment, and deformation of the wing leading edge and spar between ribs 1–3 on both wings. A maintenance inspection found no evidence of any pre-existing technical defect. The aircraft required repair by an authorized maintenance organization.
Probable Cause
The accident was caused by the failure to manage the landing maneuver after the winch disconnection, resulting in the glider impacting the ground hard.