Event Summary
The captain reported a normal flight and a stabilized landing approach, with wind directly down the runway. As the airplane decelerated through 70 knots indicated airspeed, the first officer heard a 'loud bang,' and the airplane began 'listing heavily to the right and drifting to the right.' The pilots determined that the right main landing gear (MLG) had collapsed and ordered an evacuation.
Examination Findings
The National Transportation Safety Board (NTSB) Materials Laboratory examined the broken right MLG forward trunnion bearing support fitting (FTBSF). The failure was determined to be the result of stress corrosion cracking.
Maintenance History
The right MLG was last removed for overhaul on April 8, 1988, which was 18,188 cycles before the accident. The right MLG FTBSF was last ultrasonically inspected in May 1993, 7,634 cycles before the accident. A Service Bulletin dated March 8, 1990, recommended that MLG FTBSFs be ultrasonically inspected after 12,000 flight cycles and every 6 months or 1,500 flight cycles thereafter, until the part was replaced or a preventative modification was done.
Probable Cause
The probable cause of the accident was the failure of the right main landing gear forward trunnion bearing support fitting due to stress corrosion cracking.