Amateur-built RV6A N215DG accident near Deckerville, Michigan

Probable cause

The in-flight loss of engine oil after the oil filter separated from the engine adapter assembly because of an incorrect modification of the oil filter adapter assembly, which resulted in a precautionary landing in a field.

NTSB analysis

The pilot reported that, while in cruise flight, he smelled an odor and subsequently confirmed that the engine had lost oil pressure. The pilot believed that the airplane would not be able to reach an airport, so he decided to shut down the engine and make a precautionary landing to a nearby dirt road. Shortly before touchdown, the pilot saw obstacles near the road, so he banked the airplane left toward an open field to avoid them. The airplane landed hard in the field and subsequently nosed over.

A postaccident examination revealed that the lower fuselage and the sides of the fuselage were covered in engine oil. Further examination established that the oil filter had disengaged from the adapter assembly and was the source of the loss of engine oil during the accident flight. The oil filter adapter assembly had been modified for a spin-on oil filter; however, the modification had not been completed in accordance with the installation instructions, and, as such, an incorrect oil filter had been used. It is likely that the incorrect modification of the oil filter adapter assembly resulted in a lack of proper thread engagement with the adapter heli-coil, the subsequent separation of the oil filter, and the corresponding loss of engine oil during the accident flight. A review of the engine maintenance logbook established that the incorrect oil filter adapter assembly modification and the corresponding incorrect oil filter had likely been used since the last engine overhaul, which was completed 18 years before the accident. The engine had accumulated 627 hours since the last overhaul.

Text from the NTSB. Open the NTSB docket for CEN15LA421 for the full record.