What happened
On July 2, 2016, at approximately 09:55 LMT, a training flight was being conducted at the Pobiednik Wielki (EPKP) aerodrome near Krakow. The flight involved an instructor and a student pilot operating an SZD 9 Bis 1E Bocian, registration SP-2762, using a winch launch method.
During the launch sequence, the instructor requested that the winch operator increase the speed of the pull. As the aircraft accelerated and lifted approximately 0.5 meters off the ground, the tension on the winch line suddenly dropped. This loss of tension caused the winch line parachute to deploy and drift rapidly toward the left wing of the glider. Although the instructor successfully released the line and applied the brakes, the parachute and a portion of the line draped over the leading edge of the wing, causing a puncture approximately 5 cm in diameter.
The investigation
The investigation focused on the communication between the glider and the winch operator, as well as the physical configuration of the winch line. It was established that the winch operator was not wearing radio headphones at the time of the launch. Consequently, the audio from the glider's transmissions, which was being played through the winch's cabin speaker, was difficult to understand once the engine reached high RPMs.
Furthermore, the investigation examined the setup of the winch line. The segment of the line between the parachute and the attachment point was approximately 12 meters long and lacked protective sleeving.
Findings
- Failure to follow established procedures by the winch operator regarding radio communication protocols.
- The winch line lacked sufficient length and protection; the investigation noted that if the line segment had been approximately 20 meters long and encased in a protective garden hose sleeve, the risk of the line striking the aircraft would have been significantly reduced.
- The use of a protective sleeve would have provided greater separation between the line and the glider by adding weight and stiffness, and would have prevented the line from becoming lodged in the gap between the aileron and the wing.