Siai-Marchetti S205-22R N729WA accident near Okeechobee, Florida

Probable cause

A partial loss of engine power due to a failure of the drive bearings in the alternator drive system. Contributing to the accident was the inadequate maintenance.

NTSB analysis

According to the pilot, during climbout, the engine lost partial power and was running rough. The pilot was unable to restore the engine to full power and made a forced landing in a river. Examination and partial disassembly of the engine revealed that the alternator drive adaptor did not function, the alternator drive gear exhibited extensive wear, and the gear teeth were smeared. The alternator drive bearings were not present, and metal particles were found throughout the oil system in the engine. In addition, the engine alternator drive belt that was driven by the engine was not located and the alternator adjustment was on the maximum setting. According to the engine maintenance log, the alternator was replaced by the pilot/owner and was signed off by an airframe and powerplant mechanic. The airplane had accumulated 2 hours of flight time since the alternator was replaced by the pilot/owner. It is likely that the added pressure to the crankshaft from the alternator drive shaft and the metal in the engine resulted in the engine losing partial power.

Text from the NTSB. Open the NTSB docket for ERA12LA071 for the full record.