What happened
On 29 May 2020, a SCHEMPP HIRTH - DISCUS 2C glider, registration D-KCHR, was performing a local flight at Nogaro aerodrome when it became part of an uncontrolled descent. The glider was being towed by an amateur-built aircraft, registration F-PCBA.
During the initial climb, the tug pilot executed two left turns followed by a right turn to seek an updraft. During this final turn, the glider rose above the level of the tug aircraft. The tug pilot notified the glider pilot of this "high position" via the radio frequency. However, the glider pilot was unable to reach the cable release controls.
Shortly thereafter, the tug aircraft suddenly entered a steep nose-down attitude. The resulting tension caused the tow cable to break. While the tug pilot managed to perform a pull-up maneuver to avoid the ground, the glider pilot could not regain control. The glider struck trees before colliding with the ground, resulting in the glider being destroyed and the pilot suffering severe injuries.
The investigation
The BEA examined the aircraft, the tow cable, and the flight data. The investigation focused on the mechanics of the seat adjustment in the glider and the physical failure of the tow rope.
Investigators found that the tow cable had failed due to tensile overload at the knot on the tug-side end. Regarding the glider's cockpit, while the seat adjustment mechanism showed no mechanical defects, it was noted that if the lock is not properly engaged, a sudden movement can cause the backrest to slide into the fully reclined position. In this instance, the backrest was found in the fully back position, which likely prevented the pilot from reaching the release controls.
Findings
- The primary contributing factor was the tug pilot's decision not to release the cable immediately upon noticing the glider had risen above the aircraft.
- The glider pilot was unable to operate the release mechanism because the seat backrest had moved to the fully reclined position, likely due to an improperly locked seat adjuster.
- The sudden nose-down pitch of the tug aircraft caused the tow cable to experience extreme tension, leading to its breakage.