Accident Details
The aircraft was in cruise flight about 10 miles from an island when a puff of smoke emanated from the engine cowling and the engine began to run rough. The pilot reported that the aircraft could not maintain altitude and subsequently ditched in the ocean about 100 yards off shore.
Engine Examination
The engine was disassembled for inspection. The number one and number two connecting rods were found fractured. Heat discoloration was observed on the number two bearing. Heavy fretting was found on the number two bearing surface and the associated crankcase bearing journal support. Additionally, the number three and number four cam shaft journals were observed to be visibly out of round, with heavy wear noted.
Maintenance Records
Examination of the engine log book and the operator's maintenance records revealed that the cylinder base seal for the number two cylinder was replaced on May 25, 1993, approximately 55 hours prior to the accident. According to the records, the number two cylinder base seal 'O' ring was replaced by the aircraft owner, and the work was signed off by an FAA Repair Station inspector.
Findings
The investigation documented the fractured connecting rods, bearing damage, and cam journal irregularities. The maintenance records indicated a recent cylinder base seal replacement, though no causal link was established.