What happened
During taxi for takeoff, the right main landing gear of the aircraft failed and collapsed. The incident resulted in damage to the aircraft.
The investigation
An examination of the fractured landing gear revealed that small subsurface inclusions were present near the fracture origin. A dark spot observed on the fracture surface showed a region with intergranular fracture features at the origin, alongside other areas of fatigue and intergranular fracture. Outside of this dark spot, the fracture features were consistent with overstress.
Testing for dissolved hydrogen content revealed levels ranging from 1 to 5 ppm. Additionally, residual stress tests indicated that the cylinder contained compressive stress layers on the outer surface, which were consistent with shot peening. The recorded stress profiles showed maximum compressive stresses of 200 to 250 ksi, transitioning to residual tensile stresses at a depth between 0.01 and 0.02 inch below the surface.