Cessna 182 N182EF accident near Carlsbad, California

Probable cause

The fatigue failure of the crankshaft. Contributing to the accident was the undocumented installation of the supercharger, which resulted in increased stress on the crankshaft.

NTSB analysis

The pilot stated that during the flight, the airplane’s engine started to run rough. Despite troubleshooting, the engine roughness increased followed by “flash explosions” from the engine and the smell of oil in the cabin. The engine lost total power, and the pilot performed a forced landing to an interstate highway. The airplane landed hard, which resulted in substantial damage to the fuselage.

A postaccident examination of the engine revealed that the Nos. 5 and 6 connecting rods separated from the crankshaft. The crankshaft separated into three sections. One of the separations was at the crankshaft cheek forward and adjacent to the No. 3 bearing journal, and the separation surfaces displayed beach marks consistent with fatigue cracking. Metallurgical examination revealed that the fracture appeared to initiate below the outer nitride layer near an oxide inclusion within the metal.

The engine was overhauled and converted from the original Continental O-470-U engine to a PPA O-470-50 engine per a supplemental type certificate (STC). Additionally, a supercharger was installed on the engine, which was not part of the engine conversion STC. No logbook entries were found regarding the installation of the supercharger. It is likely that the installation of the supercharger contributed additional stress to the crankshaft during operation, which resulted in the separation of the crankshaft and subsequent catastrophic engine failure.

Text from the NTSB. Open the NTSB docket for WPR20LA042 for the full record.