The pilot was landing the airplane on the runway at an ultralight airfield. After the airplane touched down, the left main landing gear collapsed at the bottom end of the strut. The airplane ground looped, and the right wingtip struck the ground. The pilot stated that the landing was smooth and gentle, not hard, and that there was no side load on the landing gear at touchdown. He added that he suspected that a previous landing may have been hard, which resulted in a crack in the landing gear.
An examination of the left gear revealed that the upper/outer strut tubing was broken, and the lower/inner strut tubing was bent. There was no evidence of fatigue. It could not be determined if the crack occurred as a result of the accident or was preexisting.
