Incident Overview
A pilot reported landing a rental fixed-gear airplane "somewhat hard," which resulted in the collapse of the left main landing gear. The aircraft was equipped with fixed landing gear, and the left main gear casting, attached to the aft side of the wing spar by eight bolts, failed during the landing.
Examination Findings
Postaccident examination focused on the landing gear attachment hardware. On the left main landing gear, which failed, four lower attach bolts were inspected: two were absent and not located within the wing, a third bolt was missing its head, and the fourth was loose. All four upper attach bolts on the left side were also found loose. Additionally, fretting was observed at the casting-to-spar interface, and the bolt holes were elongated.
In contrast, the right main landing gear, which did not fail, had all eight attachment bolts loose as well. The right gear remained intact during the incident.
Maintenance and Regulatory Context
According to the investigation, there are no Airworthiness Directives or Service Bulletins in effect concerning the landing gear-to-wing spar attachment for this model aircraft. The manufacturer's 100-hour inspection checklist instructs maintenance personnel to inspect gear struts, attachments, torque links, and bolts for condition and security.
Conclusion
The incident was precipitated by a hard landing that caused the left main landing gear to collapse. The postaccident examination revealed widespread looseness and missing hardware in the landing gear attachment bolts on both sides, indicating a lack of proper security prior to the flight.