Incident Description
On 5 July 2018, at approximately 18:30 local time, a Piper PA-28-140 (registration YL-JKV) was conducting touch-and-go landing exercises at Spilve airfield. After climbing to 1,000 feet, the pilot noticed vibration on the right side of the aircraft. The passenger visually confirmed damage to the right main landing gear. To minimize the consequences, the pilot decided to land at Ādaži airfield, which has a grass runway. The emergency landing was successful.
Aircraft Damage
Post-landing inspection revealed that the right main landing gear strut fairing was bent forward, and the attachment lugs of the shock strut cylinder were fractured. The wheel was held only by the brake hose. The aircraft sustained minor structural damage, deemed repairable.
Investigation and Analysis
The Latvian Transport Accident and Incident Investigation Bureau (TAIIB) conducted the investigation. The damaged shock strut cylinder was sent to the Riga Technical University for metallurgical examination. Analysis showed that the fractures had a low-cycle fatigue character, resulting from varying loads during operation. A crack had developed in the lower part of the attachment lugs and propagated over time. The crack was not detected during routine inspections. The material was a cast alloy with a fine-grained surface layer, which may have contributed to crack initiation.
Probable Cause
The fracture of the right main landing gear shock strut attachment lugs was due to low-cycle fatigue caused by varying loads during operation. A crack developed and propagated unnoticed during routine inspections, leading to failure.