On May 24, 2015, about 1445 pacific daylight time, a Czech Aircraft Works Spol Sro SportCruiser airplane, N642JB, experienced a nose gear collapse during landing at Fresno Chandler Executive Airport, Fresno, California. The solo pilot was not injured. The airplane was registered to a private owner and was operated by the pilot as a 14 Code of Federal Regulations Part 91 personal flight. Day visual meteorological conditions prevailed for the flight, with no flight plan filed. The flight departed from Fresno Chandler Executive Airport (FCH), and remained in the traffic pattern. According to the pilot, on the third landing, as the nose gear touched down, an immediate shimmy developed that sounded "clunky." During the landing roll, the nose gear collapsed and the airplane skidded to a stop on the runway. The pilot stated that the landing flare was "normal" and the main landing gear touched down first. The pilot reported that during the first two landings there were no anomalies with the nose landing gear. The airplane sustained substantial damage to the firewall. The nose gear assembly was sent to the National Transportation Safety Board (NTSB) Materials Laboratory, in Washington, DC, for further examination. The nose gear leg assembly is comprised of one inch in diameter bent tubing (leg) with welded brackets at each end to facilitate the fastening of the nose gear leg to the fuselage at the firewall, and the wheel assembly at the opposite end of the leg. The examination revealed that the leg of the nose gear was fractured through the tube at the weld joint in the upper attachment area. Optical examinations of the fracture face revealed separation topographies, beach marks, and recontact damage consistent with progressive fatigue cracking. A closer magnified viewing uncovered multiple fatigue fracture origins at the forward toe (edge) of the assembly weld on the left side of the tube. The fatigue penetrated a total of about 50 percent of the total tube cross section and was consistent with side to side loading of the tube. The fracture through the remaining tube cross sections was consistent with overstress. AIRCRAFT INFORMATION The airplane had accumulated 870.1 total hours of operation since new. The most recent annual inspection was completed on May 11th, 2015 and the airplane had accrued 2.0 hours of operation since that inspection. During an interview with the National Transportation Safety Board (NTSB) investigator -in-charge (IIC), the airplane owner, who is a Light Sport Aircraft Repairman, stated nothing abnormal was noted with the nose gear leg assembly during the most recent annual inspection, which he performed. He also reported that the nose gear leg that was on the airplane at the time of the accident was a "second generation" nose gear (SG0270N), but further consultation with the airplane manufacturer identified the nose gear as a first generation nose gear leg (SG0040N). ADDITIONAL INFORMATION The first generation nose gear assembly that was on this airplane was manufactured by Czech Aircraft Works (CZAW), a company that became insolvent in 2009. According to Czech Sport Aircraft, who was the company providing continued airworthiness support for all SportCruiser airplanes; there have been a number of upgrades and design changes to the nose gear. On July 10th, 2014, Czech Sport Aircraft issued a service bulletin containing instructions to replace the nose landing gear with an "Improved Nose Landing Gear Assembly (SG0300N)". The service bulletin states, "Some PS-28 Cruiser / SportCruiser / PiperSport aircraft have developed cracks in the bottom side of the lower section of the nose landing gear (NLG) SG0270N. To address this potential condition, CSA has issued service bulletin SB-CR-016 that prescribes an inspection of the of the nose landing gear SG0270N. Subsequently, CSA have developed an improved NLG SG0300N, which has better fatigue-resistant properties." Compliance with this service bulletin was not required by the Federal Aviation Administration and is an "aircraft owner decision."