NTSB Identification: CHI01LA267.
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Accident occurred Monday, August 06, 2001 in Racine, WI
Probable Cause Approval Date: 04/23/2003
Aircraft: Piper PA-32-300, registration: N5481T
Injuries: 1 Uninjured.
NTSB investigators may have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The airplane sustained substantial damage during a forced landing to a soybean field after a complete loss of engine power. The pilot reported he was flying in cruise flight at 2,800 feet mean sea level. The airplane was operating normally with no abnormal engine indications. He reported that he heard a "loud bang" and experienced a complete loss of engine power. He attempted to restart the engine but with no success. He declared an emergency and executed a forced landing to a soybean field. The on-site inspection of the airplane revealed that the number 3 cylinder and connecting rod had separated from the engine. The examination of the engine revealed that all eight hold down studs on the number 3 cylinder deck were broken and exhibited fatigue fractures. The metallurgical examination of the upper front and lower front 1/2 inch thru-studs revealed they had fractured through approximately 95% and 90%, respectively, of their cross-sections by fatigue as characterized by the smooth transgranular topography and beach marks. The hardness of the studs was below the engineering drawing requirements. The examination of the thru-studs indicated that the studs were not properly heat-treated. The 3/8 inch cylinder stud fractures were secondary to the anchored thru-stud fatigue fractures. The hardness of the other thru-studs in the crankcase was also below the requirements outlined in engineering drawings. The maintenance records revealed that the engine had been overhauled at an engine overhaul facility on February 11, 1999. It had accumulated about 532 hours of flight time since the last major overhaul. The engine overhaul facility did not, and was not required by the Federal Aviation Administration regulations or the engine manufacturer's overhaul manual, to test the engine thru-studs for hardness during the engine overhaul.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The total loss of engine power during cruise flight due to the number 3 cylinder thru-studs fatigue fractures, and the thru-stud's low hardness as a result improper heat treatment of the thru-studs, and the unsuitable terrain encountered during the forced landing. Full narrative available
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