What happened
On November 5, 2016, at Nowy Targ Airport (EPNT), a training session was underway involving a HUSKY A1A aircraft performing aero-towing operations for an SZD-50-3 Puchacz glider. The objective of the flight was to train a glider pilot in handling significant turbulence, specifically simulating "halniakowe" (mountain wave) conditions.
The pilot of the towing aircraft began the simulation with gentle maneuvers at an altitude above 300 m AGL, gradually increasing the intensity of the maneuvers as the aircraft climbed. While the aircraft was at approximately 350 m A-GL, the towline became detached from the aircraft's winch mechanism. As the line trailed behind, it became entangled around the right wing and the horizontal stabilizer of the glider. The glider crew, noticing the entanglement, maintained a controlled flight and performed a safe emergency landing back at the aerodrome. No injuries were reported, and the glider sustained no damage.
The investigation
Following the incident, the PKBWL examined the aircraft and the equipment involved. An inspection of the SZD-50-3 Puchacz revealed that the towline had indeed wrapped around the horizontal and vertical stabilizers. Upon inspecting the HUSKY A1A, investigators determined that the towline had not actually snapped; instead, the knot securing the line to the winch mechanism had come undone during the flight.
Findings
- The primary cause of the incident was the improper securing of the towline to the winch mechanism on the towing aircraft.
- The detachment occurred due to the increased mechanical loads experienced during the simulated turbulence maneuvers.
- A contributing factor was that the pilot did not verify the integrity of the towline attachment prior to the flight, as the winch area is difficult to access for inspection.
Safety action
- The Flight Safety Team of the Nowy Targ Aero Club recommended that the towline attachment to the winch be inspected before every flight day.
- Following the investigation, a permanent towing attachment was installed under the aircraft's tail to facilitate easier inspections and more efficient line replacement.