Damage and Initial Observations
The airplane sustained damage when the right main landing gear failed and collapsed during taxi for takeoff. Examination of the fractured landing gear components was conducted to determine the nature of the failure.
Fracture Surface Examination
A dark spot observed on the fracture surface indicated a region with intergranular fracture features at the origin of the fracture. Other areas of the fracture surface exhibited fatigue and intergranular characteristics. Outside the dark spot, the fracture features were consistent with overstress.
Metallurgical Analysis
Further examination of the fractured landing gear revealed the presence of small subsurface inclusions in the area near the fracture origin. Dissolved hydrogen content testing showed hydrogen levels ranging from 1 to 5 parts per million (ppm).
Residual Stress Testing
Residual stress tests indicated that the cylinder had compressive stress layers at the outer surface, consistent with shot peening. The stress profiles displayed maximum compressive stresses of 200 to 250 ksi (kilopounds per square inch), transitioning to residual tensile stresses between 0.01 and 0.02 inch below the surface.