What happened
On July 15, 2011, a Standard Cirrus CS 11-75L glider, registration OK-5147, was involved in an accident during a local flight at Havlíčkův Brod airport. The glider was being towed by a Zlin Z 226 aircraft. During the takeoff roll, the pilot noticed an unusual, excessive climb rate. Upon realizing that the flight controls were unresponsive, the pilot released the tow cable at approximately 100 km/h in an attempt to abort the takeoff.
However, the loss of longitudinal control had already occurred. The glider continued to climb uncontrollably, lost airspeed, and subsequently struck the ground at a steep angle. The impact shattered the cockpit canopy and damaged the lower fuselage. The pilot sustained minor injuries during the crash.
The investigation
The ÚZPLN investigation focused on the mechanical state of the aircraft and the assembly process. Investigators examined the horizontal stabilizer and the attachment mechanism on the vertical fin. The inspection revealed that the locking pin had been incorrectly positioned. Specifically, the end of the locking lever's extension tube was placed on the opposite side of the pin relative to the required secure position.
While the pilot and an experienced assistant had performed a visual and physical check of the assembly, they failed to notice that the pin was not properly securing the hooks against the pins. The investigation also reviewed the pilot's experience, noting that while qualified, the pilot had very limited flight time specifically on this glider model.