What happened
The pilot was operating an aircraft when the engine experienced a sudden failure, necessitating a forced landing. The event occurred during flight operations, requiring immediate action to ensure the safety of those on board.
The investigation
A thorough examination of the failed engine component was conducted to determine the root cause of the malfunction. Investigators focused on the number 2 cylinder connecting rod lower yoke, which was found to be fractured.
Metallurgical analysis of the broken part revealed significant wear patterns. The inside surfaces of the yoke exhibited rotational polishing and galled spots, indicating abnormal contact during operation. These signs pointed to progressive wear that eventually compromised the structural integrity of the component.
Findings
The metallurgical examination confirmed that the fracture was a fatigue failure. The crack originated at the inside surface of the yoke and propagated until complete separation occurred. This type of failure is typically associated with cyclic loading over time, leading to material weakness before sudden breakage.
The investigation concluded that the mechanical failure of the connecting rod lower yoke was the primary factor in the engine stoppage. The presence of rotational polishing and galling suggests that lubrication or alignment issues may have contributed to the accelerated wear, though the direct cause was the fatigue fracture itself.