On April 26, 1999, at 0930 central daylight time, a Cessna 206H, N42122, registered to Palwaukee Aviation, experienced an aileron control failure during the run-up flight control checks prior to takeoff. The incident occurred at the Palwaukee Airport, Wheeling, Illinois. The airplane was not damaged. The pilot and passenger were not injured. The 14 CFR Part 91 positioning flight was operating in visual meteorological conditions and no flight plan was filed. The planned destination was Naperville, Illinois. The pilot reported that he was unable to obtain left aileron up movement. He taxied the airplane to a maintenance facility where it was determined that the aileron had 4 degrees of up travel. Normal travel is 20 degrees +/- 2 degrees. Further inspection revealed that one of the aileron control bellcrank stop bolt/jam nut assemblies was loose allowing the stop bolt to rotate out of the threaded boss. This restricted the aileron movement. The three other stop bolt/jam nut assemblies were also inspected and were found to be loose. The airplane is a 1999 model, s/n 25, which had a total of approximately 11 hours on it at the time of the incident. In response to this incident Cessna Aircraft Company contacted all Cessna 206H and T206H owners/operators and informed them of this occurrence. Cessna Aircraft Company then issued Special Service Project SSP99-27-02. On June 21, 1999, the Federal Aviation Administration issued Airworthiness Directive, 99-13-04, effective July 13, 1999. The AD requires "...inspecting the left and right wing aileron control bellcrank stop bolts and lock nuts for flush and tight contact with the surface of the threaded boss on each end of the yoke assemblies, and accomplishing follow-on and corrective actions, as applicable."