Event Description
During landing rollout, the right main landing gear (RMLG) collapsed. The captain stated that the first officer completed a normal landing. When the captain took control of the airplane, "the aircraft dropped sharply to the right and we began skidding down the runway with a continuous warning horn." The captain continued braking, and the aircraft came to a stop on the runway centerline with a significant right lean.
Materials Examination
According to the NTSB Materials Laboratory Factual Report, the outer cylinder of the RMLG was fractured through the transition area above the fused section. The fracture was located approximately 19 inches from the upper end of the cylinder. The report noted that the fracture initiation point "lies in the parting plane for the cylinder forging. The dark spot [fracture initiation point] was orientated transverse to the gear about 28 7/8 inches from the lower end of the cylinder."
Fracture Characteristics
Examination of the fracture sample revealed multiple inclusions and intergranular cracks. The inclusions were mostly oxides of aluminum and calcium, with some containing small sulfides of iron and manganese. The report indicated fracture features consistent with overstress separation "emanating from the dark spot [fracture initiation point] with mostly ductile dimple formations and some cleavage like features."