On March 14, 2000, about 1620 central standard time, a Beech 58, N225TA, registered to and operated by Flight Express Inc., as a Title 14 CFR Part 135 on demand air taxi flight, had a right main landing gear collapse during the landing rollout at Memphis International Airport, Memphis, Tennessee. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed. The aircraft received minor damage and the airline transport-rated pilot, the sole occupant, was not injured. The flight originated the same day from Fort Smith, Arkansas, about 1457. The pilot stated that after the flare, and during the landing rollout he felt the right wing begin to sink, and the airplane started to turn to the right. The pilot further stated that he pulled back on the yoke, and applied left aileron, and noted that he had a green landing gear light. He said he was about to apply power to go around, but he saw that the propeller was damaged, and seconds later the right wing contacted the runway. The airplane then exited the north side of the runway. According to an FAA inspector, company maintenance personnel examined the right main landing gear and found that a dynamic brake relay which provides a momentary surge of reverse current to the landing gear for positive stopping, once the gear has reached either a full up, or a full down position, was found to be defective. This defective part allowed the motor to drive the gearbox past prescribed limits, inducing a bend into the right main gear connecting rod. Once gear down had been selected, the rod had a compression load, which caused it to bend even further, and not extend the gear.