On September 28, 2002, approximately 1040 central daylight time, a Cessna 421B twin-engine airplane, N7926R, was substantially damaged following loss of control after the left main landing gear separated during a hard landing at the Mineral Wells Airport (MWL), Mineral Wells, Texas. The commercial pilot and the five passengers were not injured. The airplane was registered to and operated by Dosmatic USA Inc., of Carrollton, Texas. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The flight departed the Arlington Municipal Airport, Arlington, Texas, approximately 1000, and was destined for Mineral Wells. The pilot reported that the flight approached MWL from the east, entered a left downwind for runway 13, and "the approach and landing were normal." During the landing roll, after touchdown on runway 13, the left wing dropped. The aircraft slid off the left side of the runway and came to a stop shortly thereafter. A pilot-rated passenger, who was seated in the right front seat during the accident, stated that the landing was "normal, [and] the left wing dipped after touchdown like the landing gear gave way." A witness, who was a pilot in an airplane at the approach end of runway 13, reported that "the approach of the airplane appeared normal until the aircraft was about 5 to 10 feet in the air, at which time the aircraft descent rate started to accelerate. The airplane touched down at a higher than normal sink rate." The airplane bounced after touchdown, and the left main landing gear appeared to collapse. The right main landing gear failed as the airplane departed the runway. "In my opinion it was a hard landing which would require at least a visual inspection before flying again." Examination of the left main landing gear assembly revealed that the left bellcrank was fractured. According to a metallurigist, the fracture surface displayed 45 degree shear lips that was consistent with overstress. At 1053, the Mineral Wells weather observation facility, located at the airport, reported the wind was calm.