Factual Information
On 15 July 2011, at 13:41 UTC, a Standard Cirrus CS 11-75L glider, registration OK-5147, operated by Aeroklub Praha Letňany o.s., was taking off from runway 29 at Havlíčkův Brod Airport (LKHB) behind a tow plane. During the takeoff roll, the glider pilot noticed that the elevator control was unresponsive and the glider continued to pitch up abnormally. The pilot released the tow rope at approximately 100 km/h and attempted to abort the takeoff. The glider stalled and impacted the ground. The pilot sustained minor injuries and was treated at a hospital in Havlíčkův Brod. The glider was substantially damaged, with the forward fuselage crushed and the canopy shattered. The separated horizontal stabilizer and vertical fin were found undamaged.
Sequence of Events
The glider had been assembled earlier that day by the pilot with assistance from another person experienced with the type. The horizontal stabilizer was mounted and checked visually and by applying upward pressure; however, both individuals later admitted they missed the incorrect position of the cotter pin relative to the locking lever. The glider remained parked on the airfield until the accident flight. The pilot performed four training flights on another glider type before this flight. After the tow plane landed from a previous tow, the glider was positioned on the runway and the pilot performed pre-takeoff checks. During the roll, the glider deviated to the right, then after becoming airborne at about 2 m, it pitched up excessively. The pilot attempted to counteract with forward stick but the controls had no effect. Realizing the elevator was not responding, he released the towrope at about 100 km/h, but the glider continued to pitch up, stalled, and fell to the ground.
Findings
Post-accident examination of the glider revealed that the horizontal stabilizer had separated from the fin in flight. The locking mechanism of the stabilizer was functionally normal, but the end of the locking lever's extension tube was found positioned in front of the cotter pin (on the opposite side from the pin), indicating that the hooks were not properly engaged with the pins and the stabilizer was not correctly secured. The glider's elevator control system was continuous and undamaged from the cockpit to the attachment point of the stabilizer. The tow plane, a Z 226 (OK-JGT), was properly equipped for glider towing and the pilot reported a normal takeoff run until he saw the glider pitch up in the mirror; he continued the tow and landed without further incident.
Meteorological Conditions
At the time, the aerodrome flight information service (AFIS) reported CAVOK conditions with wind from 240° at 8 knots and QNH 1018 hPa.
Injuries
The pilot was the sole occupant and sustained minor injuries.
Damage to Aircraft
The glider's forward fuselage was crushed, the canopy fragmented, the cockpit instrument panel displaced, and the landing gear control rod bent. The horizontal stabilizer and fin were undamaged. No other property was damaged.