Incident Overview
During the touchdown phase of a landing at the completion of a glider tow flight, the left main landing gear separated from the aircraft. The separation occurred just outboard from the fuselage attachment point.
Examination Findings
A detailed examination of the fracture area revealed that the spring gear had failed due to fatigue. Additionally, there was evidence that grinding had been performed on the spring gear during maintenance. This grinding resulted in overheating of the steel, which subsequently caused changes in its microstructure.
Conclusion
The fatigue failure of the spring gear, combined with the detrimental effects of maintenance grinding that led to overheating and microstructural changes, resulted in the separation of the landing gear.