On October 23, 1993, at 1600 hours Pacific daylight time, a Cessna 150K, N6067G, nosed over and collided with the runway surface after an on-ground loss of control on runway 06 at the California City Municipal Airport, California City, California. The pilots were conducting a visual flight rules instructional flight. The airplane, operated by Van M. Pray, Jr., California City, was substantially damaged. The certified flight instructor (CFI) and student pilot were not injured. Visual meteorological conditions prevailed at the time. The local flight originated from the California City Municipal Airport at 1500 hours. The airplane was returning from the local practice area and entered the airport traffic pattern for the purpose of practicing touch-and-go landings. The student pilot was manipulating the controls and touched down on runway 06 without incident. During the landing roll, the student pilot told the CFI he could not steer the airplane using the pedals. As the CFI started to take the controls, the airplane shuddered. The airplane's nose pitch down, and veered to the right with the right wing touching the ground as the airplane came to a stop. The airplane was examined by an airframe and powerplant mechanic after the accident. According to the mechanic, the bolt that forms the nose gear axle and holds the nose wheel to the nose gear fork had backed out. The AN310-5 nut that retains the bolt and cotter pin were missing. The airplane was last examined during a 100-hour inspection on September 24, 1993, about 91 flight hours before the accident. The mechanic who performed the inspection told the National Transportation Safety Board investigator during a telephone interview that he did not recall replacing the cotter pin that keeps the AN310-5 nut from turning on the axle bolt. The mechanic indicated the cotter pin may have been missing since the 100-hour inspection.