On March 20, 2014, about 1205 eastern daylight time, a Cessna 421B, N5929M, operated by a private individual, was substantially damaged while landing at the Charleston International Airport, Charleston, South Carolina. The commercial pilot and two passengers were not injured. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed for the flight that departed the Jim Hamilton L.B. Owens Airport, Columbia, South Carolina. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91.According to a Federal Aviation Administration (FAA) inspector, the airplane was landing on runway 3, a 7,000-foot-long, 150-foot-wide, concrete runway. The pilot reported that he confirmed the three landing gear indicators were "in the green" while on approach, and that he performed a normal touchdown. As the airplane began the landing roll, the right main landing gear collapsed. The airplane then veered to the right and struck two runway lights, which resulted in substantial damage to the right wing rear spar. Examination of the airplane by an FAA inspector revealed that the right main landing gear down lock bellcrank was fractured and had separated from its respective trunnion. The bellcrank bolt remained installed; however, it was sheared at the bolt head consistent with overload. The trunnion forward attach point for the bellcrank was broken and not recovered. The upper end of the bellcrank remained attached to the outboard push-pull tube. The lower end of the bellcrank which attached to the rod end fitting at the lower side link was broken consistent with a ductile tension failure. Damage to the landing gear precluded the ability to functionally check or verify the landing gear system rigging. According to a representative from Cessna, the fracture location was consistent with the additional stresses that would have been placed on the bellcrank with the landing gear having not been properly rigged. Review of maintenance records revealed that the airplane had been operated for about 4 hours since its most recent annual inspection, which was performed on January 2, 2014. At that time, maintenance was performed on the airplane which included adjustment of the right main landing gear travel.