Incident Description
According to the pilot, during the landing rollout, as the airplane decelerated to 40 knots, a vibration was felt in the airframe. As the airplane continued to slow, it began to pull to the left. The flight crew stopped the airplane on the runway.
Post-Flight Examination
During the post-flight examination, the pilot discovered that the left main landing gear had turned 90 degrees to the left. The examination also revealed a fatigue fracture in the left main landing gear socket assembly.
Fracture Analysis
Examination of the socket assembly fracture revealed two fatigue regions. These regions initiated from the lower corner lug base radii and along the left and right base radii with multiple origins. Both the lower lug corner radii were confirmed to show marks consistent with repair blending.
Repair Procedure Evaluation
According to the blend repair procedure, the surface is to be blended to a surface finish comparable to that produced by 250 grit sand paper. A comparison was made between the surface finish in the repair area and the surface produced by 240 grit sand paper on the part, which is slightly coarser than the 250 grit required. The surface finish in the repair region was much rougher than that produced by 240 grit sand paper.