The pilot had been airborne for about 45 minutes practicing turns and instrument approaches in VFR condition. He had completed a practice instrument approach to runway 1, was following the published missed approach, and the flight had attained an altitude of about 500 to 600 feet when he reported that he heard a "...loud pop, and the engine quit immediately...[without] warning of the impending engine stoppage." He declared an emergency, was cleared to land, turned left onto a short base leg to runway 1, could not maintain altitude, and he could not make it to the runway. The pilot elected to land in a field, and impacted with trees short of the runway threshold. An engine disassembly revealed that the engine failure was due a broken crankshaft gear bolt, and the separation of the crankshaft gear from the rear of the crankshaft. A laboratory examination of the failed crankshaft gear bolt, revealed that crankshaft bolt part number STD-2209, had failed due to hydrogen embrittlement. The NTSB Materials Laboratory's analysis found that the preponderance of evidence and reference information indicated that the manufacturing cycle (plating/bake delay/bake itself) was the most likely source of hydrogen embrittlement.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:

Index for Jun2002 | Index of months