ASK 13 glider crash after elevator disconnection during tow launch

Accident Overview and Immediate Sequence of Events On 24 February 2012 at 18:15 local time, a Schleicher ASK 13 glider registered F-CHRK was operating a dual-control instruction flight from Le Mazet-de-Romanin aerodrome. The instructor and student launched by tow. During the final part of the takeoff roll, the student reported an unusual shock while applying a pitch-up input, which the investigation considered likely to have been caused by the rear of the fuselage contacting the ground. In the initial climb, the glider was at a 45-degree pitch attitude and 140 km/h, exceeding the 100 km/h maximum tow speed stated in the flight manual. The instructor asked the student to reduce speed; the student increased pitch to do so, but the speed later rose again toward 140 km/h. When the student could not correct the speed, the instructor took control, observed an abnormal behavior, and released the tow cable at about 150 m altitude. The instructor turned left to land against the runway direction. Descent rate and indicated airspeed increased, and the instructor realized that pitch control was lost. He maintained speed near 140 km/h and deployed the airbrakes, which partially restored trajectory control. Unable to reach the runway, he turned 90 degrees left into a field. The glider touched down, bounced, and stopped a few meters later. ## Technical Findings and Maintenance History Examination of the aircraft showed that the automatic elevator connection had separated from the control linkage. The roller on the elevator fitting, which engages one of the linkages in the elevator control chain, had come out of its housing. Measurements taken on fixed points of the fuselage and the horizontal stabilizer/elevator assembly of F-CHRK, and compared with two other gliders of the same type, revealed notable differences. The cumulative discrepancies tended to place the roller in a higher position on F-CHRK than on the other aircraft. A moderate force on the F-CHRK elevator was sufficient to make the roller leave its housing. The glider had 6,884 flight hours at the time of the accident. Its last annual inspection was on 30 November 2011, and no specific work on the elevator control chain was recorded during that inspection. The aircraft had been reassembled eleven days before the accident and had flown 29 hours since. It was the instructor's fifth flight of the day in that glider and his second flight with that student. ## Safety Actions and Conclusion Immediately after the accident, the BEA issued an urgent recommendation to the AESA requesting inspections of Schleicher ASK 13 gliders to verify that the observed anomaly was not present on other aircraft of the same type. This was followed by an airworthiness directive, AD 2012-0246, requiring inspection of the automatic elevator connection on gliders of the same type and replacement if the assembly was found defective. The investigation concluded that the disconnection of the roller on the elevator fitting resulted from an inappropriate position of that roller in its housing, for a reason not determined by the investigation. The disconnection probably occurred during the combination of a vertical force following contact of the rear fuselage with the ground and a pilot command input during rotation at takeoff.