Incident Overview
On July 9, 2015, at airfield EPPT, a SZD-50-3 "Puchacz" glider was conducting a winch launch for an introductory flight. The crew consisted of an instructor in the rear seat and a trainee in the front seat. After reaching an altitude of approximately 350 meters, the instructor attempted to release the towline from the glider's hook. Despite three attempts, the release mechanism failed to disengage the line. In response, the winch operator cut the towline. The instructor then executed a landing approach toward the winch and landed the glider on the airfield with the towline still attached to the glider.
Investigation Findings
Examination of the glider's tow release hook revealed that the large ring of the towline was caught on the hook. After loosening the towline and gently pulling downward, the large ring disengaged from the hook. The engagement of the large ring was determined to be a secondary effect resulting from the glider dragging the unreleased line. The design of the large ring prevents accidental hooking onto the glider's hook in place of the small ring. The glider's hook mechanisms were inspected, the control cables between the front and rear releases were adjusted, and the hooks were cleaned and lubricated. Inspection of the small ring on the towline showed that it had become deformed. This deformation caused the small ring to jam on the hook, preventing release despite the hook being operated.
Corrective Actions
The responsible manager (AM) decided to change the supplier of the rings and towline as a preventive measure. No safety recommendations were issued by the investigation commission.