On July 28, 2004, at 2047 eastern daylight time, a Rockwell 114, N114TS, sustained substantial damage when the right main landing gear collapsed during landing rollout on runway 26R (5,000 feet by 100 feet, concrete) at Gerald R. Ford International Airport (GRR), Grand Rapids, Michigan. The pilot and three passengers were not injured. The 14 CFR Part 91personal flight departed Fond du Lac County Airport (FLD), Fond du Lac, Wisconsin, with GRR as the final destination. Visual meteorological conditions prevailed at the time of the accident. No flight plan was filed. The pilot reported that he flew a stabilized full flaps approach to runway 26 with all three green landing gear lights illuminated. He reported that the main landing gear touched down smoothly but when the nose wheel touched down, the right wing started to drop. The pilot kept the right wing up as long as possible, but it settled onto the runway when the airspeed slowed. The airplane veered off the left side of the runway. The inspection of the airplane revealed that the upper side brace of the right main landing gear was broken in half. The failed part was removed from the airplane and sent to the National Transportation Safety Board (NTSB) for metallurgical inspection. The NTSB Materials Lab examined the fractured right main landing gear upper side brace (p/n 45304-2) and the intact lower side brace (p/n 45305-2). The landing gear brace was fractured through the upper arm at approximately mid-length. An inspection of the fracture surfaces revealed that at one corner of the surface, there was a black region approximately 0.2 inch by 0.2 inch in size. The black region was a casting defect (inclusion). A dark gray region below the casting defect was observed by the use of a scanning electron microscope. The lack of ductile dimples, the multiple ratcheting marks, the difference in color, the fracture plane angle, and the flatness of features at the origin area indicate that the dark gray region below the casting defect was consistent with fatigue cracking. The casting defect region and the fatigue region together consumed approximately 10% of the cross-sectional area of the upper side brace. A search of the Federal Aviation Administration's (FAA) Service Difficulty Reporting System (SDRS) was made for similar reported failures. There were no records pertaining to the Rockwell 114 main landing gear side brace for part numbers 45304-2 or 45306-2. The airplane, s/n 14367, was manufactured in 1978 and had a total tachometer time of 2,684 hours. The last annual inspection was conducted on June 2, 2004, and it had flown 14 hours since the annual inspection.