What happened
During the landing roll, the left main landing gear of the aircraft separated from the airframe.
The investigation
A metallurgical examination conducted after the accident revealed that the fracture was caused by fatigue cracks. These cracks originated from the chamfer areas at two bolt hole locations on the inboard side of the strut. While the exact duration required for these fatigue cracks to propagate was not determined, it was noted that most of the brown region fractured during a single event.
Findings
The investigation found that because the fatigue cracks had existed for very few flight cycles, detecting them would have required a visual inspection of the lower surfaces of the spring strut immediately prior to the accident flight. Even with such an inspection, detection would have been difficult because the small fatigue cracks at the origin areas were obscured by washers and would not have been visually detectable.
Despite previous safety recommendations regarding this issue, the Federal Aviation Administration had reported that the visual inspections specified in maintenance manuals were adequate for detecting cracks in main landing gear struts, and further airworthiness actions were not deemed necessary. The NTSB maintained its position that a visual inspection alone is insufficient to detect cracks in Cessna main landing gear spring struts, though it acknowledged that statistical evidence did not currently warrant the issuance of Airworthiness Directives.