Cessna 182 accident near Mill Creek, California, May 1, 2019

The NTSB's narrative final · quoted from the NTSB record

The pilot and two passengers departed on a sightseeing flight over mountainous terrain. About 30 minutes into the flight, the engine lost partial power and smoke began to enter the cockpit. The pilot turned the airplane toward a grassy meadow for a forced landing. While approaching the field, the pilot suddenly saw power lines immediately ahead and attempted to maneuver the airplane below them. The airplane contacted the wires and came to rest inverted. Postaccident examination revealed several holes in the engine crankcase. The oil filter adapter was found loose and the fiber gasket was protruding beyond the castings. Removal of the oil filter adapter revealed that the fiber gasket was split. The failure of the gasket allowed oil to exit the engine, resulting in oil starvation and the subsequent catastrophic failure.   During postaccident testing, the gasket failure seen in the accident adapter could not be replicated, and the reason for the failure could not be determined. The testing did reveal that the adapters were difficult to install properly, and on some occasions, when the proper torque was achieved, the adapter housing could still be rotated about the hub when hand pressure was applied. In response to the accident and testing, the supplemental type certificate (STC) holder issued a service bulletin (SB) that stated that the adapter should be inspected for oil leakage and gasket damage. The SB also provided detailed instructions to eliminate and identify rotation of the housing during and after installation. The purpose of the oil filter adapter was to enable use of a conventional spin-on oil filter. The adapter was installed on the engine about 2 years before the accident; the engine had accrued about 340 hours since that time. There were no documents regarding the installation of the oil filter adapter, and it is unknown how it was installed or if new gaskets were used at the time of installation. Maintenance records indicated that the oil filter was changed 7 times between the engine installation and the accident. The last maintenance performed on the airplane was an annual inspection completed 5 days and about 9.4 flight hours before the accident. During this maintenance, the oil filter and the vacuum pump accessory driveshaft seal were replaced. It is possible that the vacuum pump seal was replaced because the mechanics thought it was leaking due to the presence of oil in the engine compartment. This may have been the first indication that the oil filter adapter was beginning to leak.

The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.