On February 24, 1995, approximately 1715 Pacific standard time (PST), a Pitts S-2B, N49335, nosed over after making a forced landing about 10 miles northwest of Spokane, Washington. The commercial pilot, who was the sole occupant of the aircraft, was not injured, but the aircraft sustained substantial damage. The practice aerobatic flight, which departed Felts Field, Spokane, Washington at about 1630, was being operated in visual meteorological conditions. No flight plan had been filed, and there was no report of an ELT activation. According to the pilot, while practicing an inverted flat spin, the propeller and crankshaft flange separated from the engine. He then recovered from the maneuver, and made a forced landing at a 780 foot model airplane runway. During the landing roll, the aircraft rolled beyond the end of the runway and the main gear settled into soft soil and the aircraft nosed over. The pilot stated that he had not been conducting the recurring (each ten hours of operation) crankshaft inspections recommended by the manufacturer in Lycoming service bulletin number 482, which relates to crankshaft flange area cracking on this model engine when it is used for unlimited-style aerobatics, including inverted spins.