On October 7, 2020, about 1550 central daylight time, an American Champion Aircraft model 7ECA, N790L, was substantially damaged when it was involved in an accident near Longview, Texas. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 maintenance flight. The pilot reported that the purpose of the flight was to break-in the freshly overhauled engine. The flight lasted about 2 hours before he returned to the airport to land. Upon landing, the airplane drifted to the left and the pilot attempted to correct with right rudder input. The right rudder pedal moved full forward and prevented use of the rudder or right brake. The airplane continued to the left, exited the runway, and impacted a ditch which resulted in substantial damage to the fuselage near the landing gear attachment. During postaccident examination of the airplane it was discovered that the MS20392-2C19 clevis pin that attached the right rudder pedal to the right brake master cylinder had disconnected. The clevis pin was found in the belly pan of the airplane. The illustrated parts manual for the airplane showed that the clevis pin was to be secured in position with an AN380-2-2 cotter key. No cotter key was found in the airplane after the accident. A review of the aircraft maintenance records showed that the most recent maintenance performed on the rudder pedals occurred during an annual inspection on September 27, 2019. The airplane had accumulated about 500 hours since that annual inspection. The airplane’s most recent annual inspection was completed on October 2, 2020.