Aviation accident IAD02FA091

the improper manufacturing of the crankshaft gear bolt, which resulted in the failure of the bolt due to hydrogen embrittlement, and the subsequent loss of engine power. Also causal was the engine manufacturer's failure to remove the affected bolts from fixed wing engines during the 4-year period that transpired between the initial failures and removal of the bolts from stock for installation, until the accident flight. A factor in the accident was inadequate oversight (lack of action) by the FAA during the 4-year period in which the bolts remained in serviceable engines.