On September 28, 2009, about 0845 Pacific daylight time, a tailwheel equipped American Legend Aircraft Company AL3 light sport airplane, N18MK, was substantially damaged following a loss of control during landing roll at the Fresno Yosemite International Airport (FAT), Fresno, California. The private pilot and his sole passenger were not injured. Visual meteorological conditions prevailed at the time of the accident, and a flight plan was not filed. The local flight, which was conducted under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91, departed FAT about 0745. In a written statement submitted to the Safety Board investigator-in-charge (IIC), the pilot reported that after making a two-point landing on runway 11R and keeping the airplane on the centerline using both rudder pedals, the tail wheel came down as the airplane slowed. The pilot stated that he then applied right rudder to maintain a straight direction, and then applied left rudder, but “…the left rudder would not move.” The pilot further stated that the airplane continued to the right, although he was applying left rudder. The pilot added, “I did a 180-degree turn to the right until coming to a full stop.” As a result of the ground loop the airplane sustained substantial damage to the left wing and fuselage. The pilot stated that he was concerned about what caused the airplane to veer to the right, the right rudder “locking down,” and the left rudder pedal being inoperative. In a statement submitted to the IIC by a certificated Federal Aviation Administration (FAA) airframe and powerplant mechanic, the mechanic reported that he completed repairs and reassembly of the airplane on May 12, 2010. The mechanic stated that prior to the installation of the original tailwheel assembly, he disassembled the unit and inspected it for any signs of damage or wear that would explain its possible failure to provide directional stability. The mechanic reported that he found little or no evidence of abnormal wear to the tailwheel yoke assembly, and that while the wheel bearings were loose causing “a bit of wobble” about the axle which may cause a shimmy, all other components were normal, and the unit showed no signs of jamming. The mechanic further reported that on May 13, 2010, he conducted a number of test flights, landing both in the “three wheel” configuration and “wheel landing” [configuration]. The mechanic stated that he also made two flights with a 190-pound passenger in the rear seat, which replicated the accident flight, and that “…the aircraft, although controllable, was ‘very twitchy’ on landing. As soon as the tail wheel touched down the aircraft attempted to ‘dart’ one direction and then the other, requiring quick rudder input to stabilize directional control.” On October 9, 2009, accompanied by the airplane’s pilot/owner, the IIC inspected the airplane at the pilot’s hangar located at FAT. The IIC confirmed the reported damage to the left wing and fuselage. Inspection and operation of both rudder pedals and associated rudder cables revealed no anomalies which would have precluded normal operation.