Incident Overview
On 18 March 2012, at Piotrków Trybunalski Airport (EPPT), a serious incident occurred involving a SZD-50-3 Puchacz glider. The aircraft was performing winch launches with a WS-01-JK winch on heading 210°. The glider was occupied by an instructor pilot and a student pilot. No injuries were reported, and the glider was not damaged.
Sequence of Events
During a routine launch, after reaching approximately 280 meters altitude and after the winch tow had ceased, the student pilot secured the airspeed by pushing the control stick forward and pulled the release mechanism three times. The winch operator reported via radio that the tow rope had not detached. The instructor then took control and attempted to release the rope, also without success. The instructor executed a 180° left turn, increasing speed to about 130 km/h.
The winch operator, observing the situation, activated the pneumatic guillotine to cut the rope. The guillotine failed to operate, and the rope remained attached. The winch operator reduced engine RPM to minimum and attempted to cut the rope again. After another unsuccessful attempt, the winch operator shut down the engine. This allowed the rope to unwind freely. The glider experienced a jerk and increased descent rate due to the drag of the trailing rope. While flying in a turn with steep bank, the glider rapidly lost altitude. A few meters above ground, the pilot levelled and touched down on the main wheel. The ground roll was only about 10 meters, as the still-attached rope slowed the glider.
Post-Incident Findings
After the incident, the glider's tow hook and the entire release mechanism were disassembled and inspected. No malfunction was found in its operation. As a preventive measure, the release force was checked at the Certified Glider Center in Jeżów Sudecki, where it was determined that the release force had been set at the upper limit of tolerance from the factory. The release force was then adjusted to the medium level. Additionally, a decision was made to replace the pneumatic guillotine with a mechanical one.
Probable Cause
The probable cause of the incident was the release force of the glider's tow hook being set at the upper limit of tolerance from the factory, combined with the malfunction of the winch's pneumatic guillotine.