What happened
On October 14, 2022, at the Rudnik airfield (EPRU), a SZD-50-3 "Puchacz" glider, registration SP-3288, was being used for aerobatic training flights. The aircraft had completed six successful flights, including both solo and dual instruction sessions, without incident.
During a routine cockpit inspection prior to a subsequent takeoff, the student pilot noticed that the right rudder pedal was in an unnatural position. The pedal had completely detached from the central floor console and was hanging only by the control cables. The instructor immediately halted all flight operations, and the aircraft was removed from service for diagnostic inspection.
The investigation
The PKBWL investigation focused on the structural integrity of the rudder pedal assembly and the aircraft's maintenance history. Investigators examined the construction of the pedal axis, a steel tube welded to the console. The analysis revealed that the axis was made of 30HGS steel, which requires specific heat treatment (normalization) to reduce welding stresses.
Review of the aircraft's history showed that SP-3288 had been involved in a significant accident in 2009, which resulted in substantial structural damage to the fuselage and wings. Investigators also reviewed the 1000-hour inspection protocols, noting that while the maintenance program required a visual inspection of the pedal assembly, it did not provide specific instructions for a detailed check of the axis itself, which would have required disassembly.
Findings
- The primary cause of the incident was progressive fatigue cracking of the rudder pedal axis, which eventually led to the axis breaking and the pedal detaching from the console.
- A prior accident in 2009 likely caused the initial damage to the pedal axis, which went undetected during subsequent repairs and scheduled maintenance.
- The high degree of airframe usage and the heavy control inputs required during aerobatic flight contributed to the failure.
- There was a lack of precise maintenance guidelines regarding the detailed inspection of the pedal assembly during 1000-hour inspections.
- The aircraft's significant service history and high total time contributed to the occurrence.