LAX99LA227

On the landing rollout the airplane veered to the left. An attempt was made to correct the travel to the left; however, a turn was initiated and the right wheel broke free. The right landing gear axle dug into the ground, and the airplane ground looped after the right wing tip struck the runway. The right axle was examined and found to have preexisting multiple-origin fatigue fractures.

On June 24, 1999, at 1808 hours Pacific daylight time, a Cessna 120, N2651N, ground looped and collapsed the right landing gear during a touch-and-go landing at the Chino, California, airport. The airplane, owned and operated by the student pilot under 14 CFR Part 91, sustained substantial damage. The pilot was not injured during the local area solo instructional flight. Visual meteorological conditions existed for the flight and no flight plan was filed. The flight had originated at the Chino airport at 1730.

The pilot stated that on the landing rollout the airplane veered to the left. He applied right rudder, which did not correct the travel to the left. He engaged the right brake, which did not have an effect on the airplane's movement to the left. The pilot reported that he was unable to perform a go-around due to the airplane's direction of travel. He kept the airplane on the asphalt, with the wings level, and applied the brakes to stop the airplane. He stated that the airplane "executed a moderate 180 [degree] turn," and the right wheel broke free. The right landing gear spar dug into the asphalt and broke free, the airplane made a turn to the right and the right wing struck the ground.

A Safety Board investigator examined the right main landing gear and noted the appearance of a crack in the right axle. The axle was sent to the Safety Board's metallurgical laboratory for examination. The examination revealed that the fracture was through the barrel near the mounting flange. A microscopic examination of the fracture faces showed a discolored crescent-shaped area consistent with a preexisting crack. A stereo microscopic examination revealed that the crescent region had fracture features typical of multiple origin fatigue cracking. The scanning electron microscope examinations on the mounting flange fracture revealed optical observations of fatigue and overstress. The examination revealed fatigue striations and ductile dimples respectively. It was also noted that a crack existed diametrically opposite of the fatigue crescent. It was also examined and found to have characteristics similar to the original fracture crescent.