Incident
A YS-11 aircraft was landing with a right crosswind. The pilot reported that the aircraft touched down on the right main landing gear first. Upon touchdown, the right main landing gear collapsed. The aircraft remained on the runway and sustained minor damage. All occupants, including 2 cockpit crew, 2 flight attendants, 7 revenue passengers, and 12 non-revenue passengers (a graduating class of flight attendants), evacuated without injury.
Investigation
Examination of the landing gear trunnion disclosed a stress fracture and heavy corrosion. The corrosion produced pitting, which can be a source of stress concentration. The landing gear had been overhauled in accordance with recommended procedures, which include corrosion preventative measures. However, the corrosion was not detected during normal inspections.
Findings
The investigation found that the landing gear trunnion had a stress fracture and heavy corrosion. The corrosion pitting could contribute to stress initiation, though the source does not explicitly state it as the cause. The corrosion remained undetected despite the gear being overhauled with corrosion prevention measures.