PIK-20D loses its left wing in an aerobatic pull-up from an undetected spar fracture

A PIK-20D broke up during an aerobatic competition at Podhořany when its left wing failed as the pilot pulled from a roll into a half-loop at about 500 m; he bailed out and landed unhurt, and the glider was destroyed. The upper flange of the left wing spar had fractured in a 2015 field accident, and the repair that followed checked the wings only by tap testing, which did not find it. For eight years it flew only thermals and local flights; this was its fourth aerobatic flight since. The right wing followed in the spin. The pilot jettisoned the canopy, took three seconds to free his straps, and his parachute was open at about 200 m.

1. Spar flange cracked in 2015, not found: In a 2015 field accident the upper flange of the left wing spar fractured. The repair inspected the wings by tap testing only, and neither it nor later inspections detected the damage.
2. Aerobatic competition sequence: At a club aerobatic competition the pilot flew the Sportsman sequence; it was the glider's fourth aerobatic flight since the 2015 repair, after years of thermal and local flying only.
3. Wing fails pulling into a half-loop: After a roll he pulled into a half-loop at about 500 m. As the load increased the cracked upper flange failed in compression, the lower flange in tension, and the spar tore along its length.
4. Break-up and left spin: The left wing separated and the glider entered a left spin. After several turns the right wing released from the fuselage, and one wing struck the elevator off its hinges.
5. Bailout, parachute open at 200 m: The pilot jettisoned the canopy, took three seconds to unbuckle against the centrifugal force and was flung clear. His parachute was open at about 200 m; he landed unhurt 30 m from the fuselage.