Bücker 131 APM HB-UUO Hard Landing at Grenchen

Incident Overview and Aircraft Details On the afternoon of 22 October 2005, a Bücker 131 APM Jungmann, registration HB-UUO, was involved in an accident at Grenchen Airport. The aircraft was owned and operated by the Segel- und Motorfluggruppe in Grenchen. The flight was a VFR training exercise for aerobatic instruction, with a student pilot in the rear seat and an instructor in the front. The student pilot held a commercial pilot license and had 482 hours of total flight time, while the instructor held a private pilot license and had over 4,100 hours of total flight time, including 600 hours on the accident aircraft type. ## Sequence of Events During the third aerobatic training flight of the day, the student pilot was instructed by air traffic control to enter the outer crosswind approach for a landing on grass runway 25L. The pilot used a continuous forward slip to dissipate excess altitude throughout the final approach. As the pilot exited the slip shortly before the runway threshold, the aircraft was at a high angle of incidence and flying at a low airspeed. Both pilots simultaneously increased engine power, and the student pilot attempted to initiate a go-around. However, the aircraft impacted the grass runway with a high sink rate, causing the landing gear to collapse. The aircraft slid on its fuselage for several meters. Both occupants were uninjured and were able to exit the aircraft under their own power. The aircraft sustained heavy damage. ## Investigation Findings The investigation found no technical defects that could have contributed to the accident. Both pilots reported no technical malfunctions. The analysis indicated that the high sink rate was caused by the large angle of incidence and low airspeed at the end of the forward slip. The instructor's intervention was too late to prevent the accident. Witnesses confirmed the pilots' accounts, noting that the aircraft was at a high angle of incidence during the final approach and that the exit from the slip was delayed. Weather conditions at the time of the accident included a southwest wind of about 5 knots with gusts up to 10 knots, visibility over 10 km, and a temperature of 17°C. The investigation concluded that weather and wind conditions had little contribution to the accident. The aircraft's maximum takeoff weight was 670 kg, and the actual weight at the start of the accident flight was 654 kg, with the center of gravity within prescribed limits.