On June 12, 1997, approximately 1000 central daylight time, a Wsk Pzl Mielec M-18 agricultural airplane, N6220C, was destroyed during takeoff following a collapse of the right main landing gear. The commercial pilot, sole occupant, received minor injuries. No flight plan was filed and visual meteorological conditions prevailed for the Title 14 CFR Part 137 aerial application flight. In a telephone interview with the NTSB investigator-in-charge, the pilot reported that, during takeoff, after the tail came up and before attaining flying speed, the right main landing gear collapsed. Subsequently, the right wheel assembly castored about 90 degrees, causing the aircraft to veer off the side of the runway, and travel about 100 yards through a plowed field. Just prior to coming to rest, the aircraft rolled inverted and a post impact fire consumed the engine compartment and hopper area. The operator, via NTSB form 6120.1/2, reported that examination of the wreckage revealed that the right main landing gear assembly had failed due to a "cracked bolt" that connected the upper and lower arms of the main landing gear strut scissors assembly. Examination of the right main landing gear assembly by a FAA inspector revealed that the right main landing gear torque link assembly attaching bolt failed. The external surface of the bolt was corroded, and the fracture surface showed evidence overload failure. The pilot reported that when the bolt failed the lower part of the main landing gear tire assembly swiveled and dragged in the dirt (as evidence by ground scars). Additionally, the inspector stated that there was no evidence of lubrication residues on the bolt and adjacent torque link assembly. According to the aircraft's maintenance manual, the main landing gear torque link assembly attaching bolt should be lubricated every 50 hours. Examination of the maintenance records did not show annotations regarding the lubrication of the aforementioned items.