On May 28, 1995, about 1040 hours mountain daylight time, N9115C, a Cessna 180, was substantially damaged during landing in Phillipsburg, Montana. The certified flight instructor (CFI), student pilot, and the passenger were not injured. Visual meteorological conditions prevailed and no flight plan had been filed. The instructional flight departed from Anaconda, Montana, about 1000 and was conducted under 14 CFR 91. According to an FAA aviation safety inspector from Helena, Montana, the student pilot attempted to land the airplane on Runway 34 at Riddick Field in Phillipsburg. After touching down, directional control was lost. The CFI attempted to regain directional control, but was not successful. The airplane began to veer off the west side of the runway and the right main landing gear collapsed. The airplane came to rest off the west side of the runway. The airplane's firewall was "crumpled." According to the CFI, the owner of the airplane asked for instruction in the airplane. The owner was a rated private pilot. Two days prior to the accident, the CFI arrived in Phillipsburg to give instruction to both the owner and a student pilot. The CFI stated: As the plane rolled forward out of the hanger I noted to [the owner] that the wheels tracked to pull the wheels together. Rolling the plane backwards tracked the wheels outward. I then gave instructions for the next two days to [the owner and another student pilot]. Seventeen landings were made. On May 28, we set up for the eighteenth landing with [the student pilot] in the left seat, myself in the right, and [the owner] sitting in the rear seat. A standard left hand pattern was flown to runway 34 ... to set up for a three point landing with full flaps. Airspeed was 60 mph on short final (power was at idle at touchdown). The airplane was lined up on the center line with the longitudinal axis parallel to the center line. The right wing was slightly low to compensate for a slight cross wind from the right, with approximately 3 knots wind out of 010 [degrees]. The aircraft was not drifting left or right at the point of touch down. After two minor bounces the aircraft remained on the ground and began to turn left. As the left turn continued I took control and applied right rudder and right brake, which had no effect. Full right rudder and more brake also had no effect. As the left turn continued the right wing began to drop aggressively, so I applied full left aileron in an attempt to level the wings. This also had no effect. At about this time the wing contacted the runway.... The wing's first contact was very close to the runway centerline.... As the slight left turn continued to the runway edge I heard a loud bang as the right main gear departed the aircraft, before the aircraft itself was off the runway. The student pilot also provided a written statement to the Safety Board. His recollections of the accident were the same as the CFI's account. The CFI stated that he did not groundloop the airplane. He stated that there was a failure in the right main landing gear where it bolts to the fuselage. He further stated that "the wheel was toed in excessively before touch down or did so at touch down." The attachment bolt and nut from the upper end of the right main landing gear, and the structural fitting from the right main landing gear attachment, were sent to the Safety Board's Materials Laboratory Division for analysis. According to the Metallurgist's Factual Report (attached): Damage was found on all of the nut threads, indicating that the nut had been fully engaged with the bolt threads when the threads were stripped.... Examination [of the fitting] revealed that all of the fractures in the fitting piece were typical of overstress separation. No evidence of preexisting fracture areas was noted. The report also stated: The location of the gaping crack, the direction of the overstress fractures on the end of the fitting, and the directions of separations of the riveted bracket piece are consistent with an overstress load applied to the fitting. According to an FAA licensed airframe and powerplant mechanic in Stevensville, Idaho, no evidence was found in the main landing gear attachment area to indicate previous damage, rework, or pre-impact mechanical deficiencies. The mechanic stated that the wheels of the main landing gear were "toed in," and that the tire tread along the outside of the wheels were "badly worn."