On August 31, 2007, approximately 1500 central daylight time, a Piper PA-30, N22HW, piloted by a private pilot, was substantially damaged when the right main landing gear collapsed during landing rollout at the Lawrence, Kansas, Municipal Airport (LWC). Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 CFR Part 91 without a flight plan. The pilot, the sole occupant on board, was not injured. The cross-country flight originated at Topeka, Kansas, and was en route to Lawrence. The pilot said he had made approximately 5 touch-and go landings within an hour at Topeka, Kansas. He then flew to Lawrence. When he lowered the landing gear in preparation for landing, he noticed in the engine nacelle mirror that the landing gear was approximately one-third extended. The pilot departed the airport area to troubleshoot the problem. During his initial attempt at lowering the landing gear manually, he noticed that the main landing gear circuit breaker had tripped. After several attempts to extend the landing gear manually, it extended about two-thirds of the way. The pilot then "pushed the gear down entirely" and a GEAR SAFE annunciation was illuminated. He confirmed gear extension by seeing it in the engine nacelle mirror. The pilot landed the airplane but during the landing rollout, the right main landing gear collapsed. Post-accident examination revealed the right wing was scraped and the aileron and flap were damaged and had to be replaced. In addition, the right main gear pushrod was bent and had pushed against and bent the support web in the wheel well. FAA Airworthiness Directive (AD) 77-13-21 part (a) requires that the landing gear system be inspected every 1,000 hours and components exceeding specified wear limits be replaced. According to maintenance records, prior compliance with AD 77-13-21 part (a) was accomplished at an aircraft total time of 4,231 hours. The total time on the aircraft at the time of the accident was 5,124 hours. During a post-accident inspection, the following parts of the main landing gear system were found to be in need of replacement due to wear: AN26-25 (bolt), 14843-16 (bushings), 14843-30 (bushings), 20737-8 (bushings), AN26-21 (bolt), 14843-60 (bushings), and 25046 (links). Piper Service Letter 782B, dated December 1, 1977, describes the reason for the inspection of the main landing gear system and addresses reports of the landing gear failing to remain down and locked during landing roll-out. The failures occurred after a normal landing gear extension failure, and extension of the landing gear by the manual system. The service letter stated (in part): "The down lock mechanism did not remain engaged due to system wear, apparently as a result of inadequate system maintenance and inspection. In some cases, chronic landing gear circuit breaker tripping preceded actual failure (collapse)."