Accident Details
On 12 July 2014, a SZD-48-3 Jantar Std 3 glider, registration SP-3688, operated by a private owner, was involved in an accident at Michałków airport near Ostrów Wielkopolski (EPOM). The 48-year-old male pilot was participating in the XXII Regional Gliding Competition in the standard class, organized by Aeroklub Ostrowski. The flight began with a tow to 600 meters, after which the pilot released and proceeded solo.
Pilot's Observations
During the flight, the pilot reported that the glider did not respond precisely to control inputs. This was his first flight that season with full water ballast tanks. He climbed to 1500 meters and performed several maneuvers to test the control system, including multiple deployments of the aerodynamic brakes. At one point, he felt significant resistance when retracting the brakes and heard a metallic sound, which he described as similar to an object rolling on a hard surface. He decided to abort the flight and return to the airport, radioing a report of a malfunction and poor response to control inputs.
Landing and Post-Flight Inspection
The landing at the departure airport was uneventful, though the pilot continued to experience resistance when operating the brakes. After landing, tests of the brake extension and retraction revealed significant resistance and metallic noises from the left wing. The brakes eventually jammed in the partially open position. An attempt to force them closed resulted in a bolt puncturing the wing skin.
Examination Findings
The glider was transported to a maintenance facility (Zakład Przeglądów i Napraw Statków Powietrznych) for investigation. A control cutout in the wing revealed a loose bolt with a bearing, identified as part of the aileron pushrod guide. A second such component was extracted using a laparoscope, along with fragments of a plastic guide. A camera inspection revealed a damaged pushrod guide on the wing closing rib. It was determined that fragments from the damaged guide had moved within the wing, causing blocking of the pushrod and the aerodynamic brake control system.
Additional Discoveries
During the investigation, the same maintenance facility found a similar issue on another SZD-48-3 Jantar Std 3 glider under repair. That glider also had a damaged pushrod guide. The guides on both gliders were made of plastic, which was suspected to be non-original. The Polish State Commission for Aircraft Accident Investigation (PKBWL) noted that modifications to the glider's construction likely occurred outside Poland, as these gliders were reportedly imported from Russia.
Type Certificate Holder Response
The PKBWL contacted Allstar PZL Glider Sp. z o.o., the Type Certificate Holder (TCH) for the SZD-48-3, who indicated that similar non-certified pushrod guides had been found on a Croatian glider (serial B-1901, built 1989) imported from the former Soviet Union. In that case, inspections in 2012 revealed that the guides were not original and were replaced with factory parts. Documentation showed that the original guides had been replaced in the former USSR under a decision by the Chief Engineer of DOSAAF USSR in 1989, likely due to a defect in the original Polish-made guides (brass bearing axes that cracked over time). The TCH stated that the replacement was not consulted with the original manufacturer and that the non-original guides should be replaced again with factory parts.
Probable Cause
Damage to the aileron pushrod guide, which led to blocking of the pushrod and the aerodynamic brake control system by moving fragments from the damaged guide.
Safety Recommendations
The PKBWL recommended that the Type Certificate Holder issue a bulletin (with the force of an EASA Airworthiness Directive) for inspection and replacement of these pushrod guides on all SZD gliders imported from the former USSR. Additionally, the competition organizer reminded pilots to conduct thorough pre-flight inspections.