On July 20, 1999, at 1128 central daylight time, a Beech 55, N56AW, nose wheel assembly collapsed during a landing on runway 20C at the Nashville International Airport in Nashville, Tennessee. The instructional flight was operated by the pilot under the provisions of Title 14 CFR part 91 with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The airplane sustained substantial airframe damage. The certified flight instructor and the commercial pilot were not injured. The initial departure time from Nashville, Tennessee, at 0900. According to the pilot, the multi-engine training flight was cleared for a landing on runway 20C. The pilot reported that the before landing checklist was completed, and the landing gear extension was verified by both pilots. The landing on the main wheels, was described as normal, but when the nose wheel was lowered on the runway, both pilots heard a "pop" followed by the collapse of the nose wheel assembly. The airplane slid 2500 feet before stopping on the runway. The post-accident examination of the airplane disclosed that the nose landing gear aft drag brace had broken. The drag brace broke at the point where the retraction rod attaches to the nose gear retract idler tangs. Maintenance history of the failed component was not available, however according to the 100 hour inspection card, a visual and security check is required for nose gear linkage components (see attached copy, illustrated parts catalog, and copy, shop manual,100-hour inspection).