On April 1, 1996, at 1355 central standard time, a Cessna 210K, N9470M, operated by a private pilot, sustained substantial damage when the right main gear collapsed on landing. The airplane landed on runway 10 (4,751' x 75' dry/asphalt) at DuPage Airport, West Chicago, Illinois. The pilot reported no injuries. The local personal 14 CFR Part 91 flight was operating in visual meteorological conditions. No flight plan was on file. The flight departed West Chicago, Illinois, about 1200. Subsequent to the accident an examination of the landing gear retraction/extension mechanism was conducted by the Federal Aviation Administration (FAA). According to the FAA inspector there were airworthiness directives (AD) pertaining the landing gear which had not been accomplished. The same inspector stated the AD's directly affected the function of the retraction/extension mechanism system. The pilot told FAA inspectors that he did not have a current biennial flight review. His FAA third class medical was issued on August 15, 1995; however, it was valid for three months and had expired at the time of the accident.