What happened
On July 9, 2015, a crew consisting of an instructor in the rear cockpit and a student pilot in the front cockpit was performing a winch launch for a training flight. The SZD-50-3 Puchacz reached an altitude of approximately 350 meters when the instructor attempted to release the winch cable. Despite three separate attempts to trigger the release mechanism, the cable remained attached to the glider.
Due to the failure to release, the winch operator eventually disconnected the cable from the winch unit. The instructor proceeded to perform a landing approach toward the winch station, still attached to the cable. Upon landing, an inspection revealed that the large wheel of the winch cable had become hooked onto the glider's release mechanism. This entanglement was a secondary effect caused by the glider dragging the unreleased cable during the flight.
The investigation
The investigation focused on why the release mechanism failed to function despite the release hook being in working order. Examination of the winch cable's small wheel revealed that it had become deformed. This deformation caused the small wheel to jam against the release hook, preventing the mechanism from disengaging the cable.
Findings
- The primary cause of the failure to release the winch cable was the jamming of the small wheel on the cable due to its physical deformation.
Safety action
- Following the incident, the responsible manager decided to change the supplier for both the cable wheels and the winch cables as a preventive measure.