On May 23, 2003, at 1340 central daylight time, an amateur built Boyle Black Eagle BE360 tailwheel equipped airplane, N72BJ, was substantially damaged when it nosed over during a forced landing following a loss of propeller pitch effectiveness near Celina, Texas. The commercial pilot, who was the sole occupant, of the airplane, sustained minor injuries. The airplane was registered to and operated by the pilot under 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and a flight plan was not filed for the personal flight. The local flight originated from the Aero County Airport (T31), near Mc Kinney, Texas, approximately 1330. The 1,222-hour pilot reported in the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) that prior to departure, the engine run-up "was normal." During the flight, "all engine parameters appeared to be normal." Upon arriving at the practice area, several aerobatic maneuvers were completed with "no apparent abnormalities." At an altitude of 2,500 feet agl, a "half loop down" was initiated at an approximate airspeed of 95 to 100 mph. At the base of the maneuver, at an approximate airspeed of 160 to 170 mph, and an altitude of 2,000 feet agl, he heard a "loud high pitch noise accompanied by a rapid decrease in airspeed." He reduced the power to idle, increased the mixture to rich and cycled the propeller pitch to high, then to low. He observed the tachometer "falling through 3,800 rpm." The pilot stated that "repeated attempts to bring the rpm within range using the throttle and propeller controls failed as the aircraft appeared to be descending between 500 and 1,000 feet per minute at an airspeed of 95 mph." During the descent, the he observed "the tachometer continuing to show the engine turning at 3,200 rpm with the throttle at idle." Subsequently, the pilot initiated a forced landing to a wheat field. During the landing roll, the left main wheel hit a hole, and the airplane nosed over and came to rest inverted. Examination of the by a Federal Aviation Administration inspector, revealed the right lower wing spar was cracked. Examination of the propeller revealed it was free of anomalies and "functioned normally." Disassembly of the propeller governor (Hartzell Governor Model Number F6-56, Serial Number D4158TJ) revealed, "small amounts of metal flakes were blocking the pressure relief valve from opening and to stick in the closed position." The propeller governor was sent to Hartzell Propeller Inc., for further examination. On October 29, 2003, at the facilities of Hartzell Propeller Inc., near Piqua, Ohio, an FAA inspector observed the disassembly, inspection, reassembly, and bench testing of the propeller governor. No scoring, foreign matter, or other damage was observed in the pressure relief valve components. Very light pitting was noted on the gear pockets. The governor was noted free of anomalies. Test results indicated the "high rpm setting was 170 rpm too high." Review of the aircraft logbooks indicated the propeller governor was rebuilt on May 9, 2001. The pilot reported the propeller governor had accumulated approximately 140 hours since the rebuild.