Beech H35 N4684D accident near Holly Lake Ranch, Texas

Probable cause

The incomplete maintenance performed by maintenance personnel, which resulted in a total loss of engine power.

NTSB analysis

The airplane’s engine lost power during the descent to the destination airport, and the airplane struck trees during the ensuing forced landing attempt. A postaccident examination of the engine revealed that the idler gear pin was not in position and no retaining bolts were found. Additionally, the nuts from the forward left, lower through bolt on the crankcase half and the forward left engine mount bolt were missing. A logbook entry indicated that the engine had been reassembled and re-installed on the airplane about 1 week before the accident due to a previous propeller strike. Based on the available information, it is likely that the improper assembly of the engine, specifically the omission of the idler gear pin retaining bolts, resulted in the idler gear falling out of its position and a subsequent complete loss of engine power.

Text from the NTSB. Open the NTSB docket for CEN12LA501 for the full record.