On August 14, 1995, at 1430 central daylight time, a Cessna 188, N53376, operated by Agricultural Aviation, Inc., sustained substantial damage when it nosed over on landing roll after a forced landing due to loss of engine power near Meade, Kansas. The commercial pilot reported minor injuries. The 14 CFR Part 137 flight departed near Meade, Kansas, on a local flight. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that while he was pulling up out of a field and starting into a turn, he heard a loud bang and felt an abrupt reduction of power. The engine cowling came loose and departed the aircraft. During the emergency landing, the airplane nosed over. The pilot reported that the entire propeller assembly was missing and that it had broken off at the crankshaft flange. An inspector for the Federal Aviation Administration reported that a propeller blade was found over a month later in a farmer's field. He reported that an examination of the blade revealed that it had broken off at the blade root. He reported that all four engine mounts were broken, and that the loose engine had ripped the cowling loose and had punctured two holes in the oil pan. The pilot reported during a phone conversation that the propeller had been leaking oil. He had sent the propeller to a propeller shop to have it inspected for leaks and cracks. He reported that the propeller shop's examination found no cracks and replaced the seals. The pilot reported that the propeller was returned to service, but after seven hours of flight the propeller failed. He reported that the propeller failed at the base of the blade just above the threads. The pilot reported that he sent the propeller blade to a metallurgical laboratory for examination. The laboratory reported that, "the propeller had failed with a transverse fracture at the base of the blade. The fracture showed a bending fatigue pattern through about 40% of the cross section. The origin of the crack was in line with the leading edge of the propeller." The laboratory's report also stated that, "the fracture probably started with a high load that created the initial crack... ." (See attachment)