Cessna 207 N1596U accident near Marathon, Florida

Probable cause

A total loss of engine power due to the failure of the No. 2 bearing, which resulted in the No. 2 connecting rod failing due to fatigue, high heat, and stress.

NTSB analysis

Shortly after departure, the engine lost total power and the pilot was forced to ditch in open water; the occupants egressed and were subsequently rescued by a recreational vessel.

Examination of the engine revealed a fracture hole near the No. 2 cylinder, which was likely the result of the No. 2 cylinder connecting rod fracturing in fatigue as a result of high heat and high stress associated with failure of the No. 2 bearing. The fatigue fracture displayed multiple origins consistent with relatively high cyclic stress, which likely occurred as excessive clearances developed between the bearing and the crankshaft journal.

The No. 2 connecting rod bearing may have failed due to a material defect in the bearing itself or due to a disruption in the oil lubrication supply to the bearing/journal interface. Either situation can cause similar damage patterns to develop, including excessive heating and subsequent bearing failure.

Text from the NTSB. Open the NTSB docket for ERA22LA097 for the full record.