Piper PA-32-300 N475RT accident near Edisto Island, South Carolina

Probable cause

A loss of engine power due to the fatigue failure of the crankshaft counterweight retaining ring and the No. 6 connecting rod.

NTSB analysis

Shortly after takeoff the engine started to “sputter,” then stopped producing power; oil then blew out of the engine cowling onto the windshield. The pilot made a forced landing in a field and the airplane contacted a wire fence, resulting in substantial damage to the airframe.

A postaccident inspection of the engine revealed that the engine crankcase was ruptured in two places near the Nos. 5 and 6 cylinders. Subsequent detailed examinations showed the Nos. 5 and 6 connecting rods were fractured and that a counterweight retaining ring (circlip) was missing its eyelets and had separated from the counterweight assembly. Additional metallurgical examination revealed that the counterweight retaining ring failed due to fatigue. The failure allowed the counterweight roller to eject from the counterweight. Additionally, the No. 6 connecting rod exhibited evidence of a fatigue failure in multiple locations and the Nos. 5 and 6 pistons showed evidence of detonation. It is likely that the fatigue failure of the retaining ring or the fatigue failure of the No. 6 connecting rod occurred and propagated throughout the engine until a catastrophic failure resulted. The failure sequence could not be determined, but it is likely that the piston detonation exacerbated the process.

Text from the NTSB. Open the NTSB docket for ERA22LA104 for the full record.