On February 4, 2005, at 1315 Pacific standard time, an Air Tractor AT-401, N4530L, came to rest in a ditch after experiencing a rudder pedal control malfunction on touchdown at Johnson Brothers Airport (61CL), a private dirt strip in Calexico, California. Frontier Agricultural Service, Inc., operated the airplane under the provisions of 14 CFR Part 137, as an agricultural spraying operation. The airplane sustained substantial damage. The commercial rated pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed for the local area flight, and no flight plan had been filed. The flight departed 61CL about 1300. In the pilot's written statement he reported that he had started operations out of 61CL about 1100. He was returning to pick up his sixth load of the day when the accident occurred. On the first flight of the day he performed the standard walk-around preflight. After startup, he taxied for takeoff and verified the flight controls were "free and easy." He flew to Johnson Brothers Airport for his first load, and returned for four subsequent loads. While on short final, the airplane encountered a left crosswind condition. He immediately applied pressure to the right rudder pedal to correct for the crosswind, but the pedal would not move. The airplane touched down on the runway, veered to the left exiting the runway, collided with a berm, and came to rest in a ditch. During the accident sequence, the left wing dragged on the ground displacing the fuselage about 60 degrees along its lateral axis. After the airplane came to a stop the pilot noticed he was still applying pressure to the right rudder pedal. He looked down and saw the rudder pedal adjusting pin contacting the aft edge of the hopper. When he released pressure on the pedal, the entire pedal assembly, to include the adjusting pin, moved to the left and returned to its normal position. The pilot further reported that a 100-hour inspection had been completed on February 1, 2005, 3 days prior to the accident. In the post examination of the wreckage, an inspector from the Federal Aviation Administration (FAA) discovered a groove in the right side of the hopper wall. The groove began at a radius in the hopper wall where the wall turned 90 degrees from a cross cockpit orientation to a longitudinal direction. When he depressed the rudder pedal, he noted that the adjusting pin contacted the groove the entire length of travel. He further noted that despite the contact of the pin in the groove, there was no restriction of movement of the rudder pedal. A gouge dimensionally identical in shape and size to the pin was observed in the hopper just to the right of where the adjusting pin contacted the groove. See photograph 2 in the docket materials for this accident. The FAA inspector noted no groove or gouge on the left side of the hopper. ADDITIONAL INFORMATION The closest official weather observation station was Imperial, California (IPL), located 10 nautical miles (nm) north of the accident site. The elevation of the weather observation station was -56 feet mean sea level. An aviation routine weather report (METAR) for IPL was issued at 1253. It stated: winds from 330 degrees at 11 knots; skies clear; temperature 22 degrees Celsius; dew point -02 degrees Celsius; altimeter 29.99 inHg. The Airport/ Facility Directory, Southwest U. S., indicated the runway was 2,500 feet long and 50 feet wide; the runway surface was dirt.