On December 27, 2003, at 0924 Pacific standard time, a Bellanca 7ECA, N53879, ground looped while landing on runway 7 at the Oxnard, California, airport. The airplane was owned and operated by CP Aviation, Inc., Santa Paula, California, and rented by the pilot for a local personal flight. The airplane sustained substantial damage. The private pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane departed Santa Paula at 0842 for a flight to Oxnard. In a written statement, the pilot reported that he took off from Santa Paula and flew to Oxnard to practice takeoffs and landings. After several successful landings and takeoffs, the pilot touched down on runway 7 and the right rudder pedal bent top down and became stuck. As a result, he was unable to maintain directional control and the aircraft ground looped off the left side of the runway. The right horizontal stabilizer was damaged during the event. The pilot stated that the clevis pin that secured the right rudder pedal to the brake cylinder arm was missing, which prevented the application of right rudder. The Oxnard airport operations officer was interviewed via telephone by the National Transporation Safety Board investigator-in-charge (IIC). He noted that there was significant right horizontal stabilizer damage. The right pant wheel was "torn off and smashed up." It appeared that the pilot was unable to maintain directional control due to the right rudder pedal clevis pin missing. He also saw evidence of aluminum shavings at the clevis pin attachment point. A Federal Aviation Administration (FAA) airworthiness inspector interviewed the aircraft operator. The operator told the FAA inspector that this airplane, and another of the same make, model, and year, is used heavily for aerobatic instruction. In the past, they have had problems with the rudder pedal pin coming in contact with a structural fuselage angle brace during full extension of the rudder pedals in aerobatic maneuvers. This contact between the pin and the angle brace progressively wears/grinds the pin down to the point where it is no longer retained in the hole and comes out. This problem was found on the sister ship to the accident airplane a few weeks before the accident and that pin was changed. The operator intended to examine the rudder pedal pins on the accident airplane in the next scheduled maintenance period. The manufacturer of the airplane, Champion Aircraft, Inc., was contacted regarding the installation of the pin. In the Citabria Parts Manual, Figure 26 (Installation Brake System-Toe) indicates that the head of the cotter key is installed with the pin inboard of the cotter key. In this model of Citabria, the battery is located in the forward section of the airplane and a fuselage angle brace is installed for support. On the right pedal of the forward seat, the clearance between the pin and the angle brace is reduced. If the pin is installed outboard of the cotter key, there is a greater clearance between the angle brace and the pin. The manufacturer indicated that the pin could be installed either way; however, Figure 26 depicted the pin as being installed inboard of the cotter key.