What happened
On October 15, 2022, a WT-9 Dynamic aircraft, registration SP-SMOK, was performing glider towing operations at Kruszyn airfield (EPWK). Following a successful initial tow, the pilot taxied to the glider's position to prepare for a subsequent launch. After attaching the towline, the pilot received radio instructions to tension the line to align the aircraft and glider for takeoff.
While tensioning the line at a speed of approximately 6 km/h, the aircraft's front landing gear strut failed. This failure caused the aircraft to pitch forward, resulting in the propeller making contact with the ground. The engine immediately shut down. The pilot successfully shut off the fuel valve, deactivated the electrical power, and exited the aircraft without injury.
The investigation
The PKBWL investigation focused on the structural failure of the nose gear strut. Examination revealed that the fracture occurred at a weld point. Investigators determined that the failure was likely initiated by a micro-crack at a geometric stress concentrator, which subsequently propagated through the metal.
At the time of the incident, the aircraft had a total time in service of 1,684 hours and had completed 6,896 landings. The investigation noted that the manufacturer had not specified a maximum landing limit or a specific service life for the nose gear strut. The most recent 100-hour inspection, which included checking the strut for damage and deformation, had been performed 74 flight hours and 529 landings prior to the event; this inspection did not reveal any visible cracks.
Following the event, the engine underwent a standard inspection for propeller strikes at an authorized Rotax service station. The engine and propeller were cleared for continued use after necessary component replacements, and no damage to the engine gearbox was found.
Findings
- The primary cause of the incident was the failure of a welded connection on the front landing gear strut due to long-term intensive use.
- The aircraft's operational profile involved frequent short flights, leading to a high number of landings relative to total flight time.
- Operating on a grass runway increased the mechanical load on the landing gear.
- The presence of a nose wheel fairing prevented the visual detection of early-stage cracks during pre-flight inspections.