On May 26, 2002, approximately 1350 Pacific daylight time, an Arctic Aircraft S-1B2 "Arctic Tern," N69AG, owned, operated and being flown by a private pilot incurred substantial damage during touchdown in a field approximately five nautical miles southwest of Tumtum, Washington. The pilot and passenger were uninjured. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal, was operated under 14 CFR 91 and the aircraft departed from a local site approximately 1100. An inspector assigned to the Federal Aviation Administration's Spokane Flight Standards District Office interviewed the pilot. The pilot reported that upon touchdown the left main landing gear collapsed, the aircraft began skidding and then the right main landing gear collapsed. The aircraft then nosed over and came to a stop. The pilot reported that he and his passenger departed from a meadow and after some local sightseeing he returned for landing. He further reported that "...just after touching down a noticeable "pop" was heard and the landing gear collapsed..." and that "...the terrain [at the landing site] was a flat dirt field..." (refer to attached NTSB Form 6120-1/2). The broken landing gear attach fitting was sent to the Safety Board where it underwent a brief metallurgical examination at the Board’s Materials Laboratory. The examination revealed fracture features and deformation typical of an overstress fracture under a combined torsion and bending load. No evidence of pre-existing cracking was noted (refer to attached report).