Piper PA-28-180 N8364W accident near Coldwater, Michigan

Probable cause

A loss of engine power due to the separation of the No. 4 piston connecting rod as a result of inadequate torque of the connecting rod bolt.

NTSB analysis

The pilot reported that he was in cruise flight at 2,500 feet above mean sea level when the engine oil temperatures started to rise. He started to divert to a nearby airport, but the engine seized and he executed a forced landing to a field. The inspection of the engine revealed a hole in the crankcase at the #4 cylinder position. The #4 piston connecting rod was found disconnected from the crankshaft, and it was deformed and bent into a “U” shape. The #4 connecting rod cap was separated from the #4 connecting rod. One of the connecting rod bolts was found sheared in half with the nut still attached to one end of the bolt. The other connecting rod bolt was not located in the connecting rod or in the rod cap. A connecting rod bolt was found in the bottom of the engine. The bolt threads exhibited some impact damage, but otherwise, the connecting rod bolt was intact and was not bent. The nut for the connecting rod bolt was not located in the engine. The engine logbook indicated that four new pistons were installed on May 31, 2003. The logbook entry did not indicate that the connecting rods had been replaced. On May 1, 2007, the #4 cylinder was replaced, but there was no indication in the logbook entry that the #4 piston or connecting rod had been repaired or replaced.

Text from the NTSB. Open the NTSB docket for CEN10LA037 for the full record.