Introduction
On 20 August 2014 at 15:30 UTC, a L-13 Blaník glider, registration OK-4832, operated by Aeroklub Plzeň Letkov, was involved in an accident at Plzeň Letkov Airport (LKPL). The glider was on a training flight practicing landing in a limited area with a student pilot and an instructor on board.
Flight Sequence
The flight was the second of two training flights that day. The first flight occurred between 15:15 and 15:22, also practicing landing in a limited area. For the second flight, the glider took off at 15:24 in an aerotow behind a WT-9 aircraft, releasing at approximately 250 m above ground level. The crew then performed several steep turns to lose altitude and set up an approach from the southeast, crossing the runway at an angle. The instructor executed a slip to increase descent rate. The glider touched down on the right edge of Runway 26 at an indicated airspeed of about 95 km/h with full airbrakes and flaps extended.
Accident
After touchdown, the glider's speed did not decrease as expected. Both pilots attempted to use the wheel brake, but it seemed ineffective. The student pilot reported that the brake lever felt as if it had no effect, and the instructor felt a sensation similar to a broken cable. The glider continued rolling straight, crossing the runway and grass area, and could not stop before reaching the edge of the airfield. It then fell from a steep drop approximately 2 m high and struck the ground nose-first, causing structural damage. The straight-line distance from the touchdown point to the impact point was about 192 m.
Damage
The accident resulted in deformations of the nose cone, fuselage bulkheads (including bulkheads No. 1, 10, 13, and 15), floor, and control rods. The right wing's root area was deformed along the leading edge between ribs No. 1 and 7, and the left wing had minor deformation near the tip (between ribs No. 29 and 30). The undercarriage appeared undamaged. A subsequent inspection by the maintenance organization found no malfunction in the wheel brake control system but identified multiple structural damages rendering the glider unairworthy.
Crew
The instructor was a 22-year-old male with a valid glider pilot license and flight instructor qualification (FI(G)). He had a total of 256 hours 20 minutes on gliders, including 35 hours 24 minutes as an instructor. He had 116 hours 30 minutes on the L-13 type. The student pilot was a 36-year-old male who had started glider training in 2014 and had accumulated 10 hours 18 minutes of dual instruction. Neither pilot was injured. Police conducted a breathalyzer test with a negative result.
Weather and Airport
The weather was CAVOK with a surface temperature of 18.6°C. Recorded surface winds were from 226° to 240° at 3.2 to 4.1 m/s, with gusts up to 7.1 m/s. The touchdown point was on the right edge of Runway 26, approximately 60 m beyond the threshold, at coordinates N 49° 43‘ 23.2“, E 13° 27‘ 22.5“. The rollout path was initially nearly straight on a course of about 038°, then slightly veered right towards the airfield edge, where a steep drop existed. The runway and operational area were dry and freshly mowed.