Mooney M20J N367MR accident near Lewiston, California

Probable cause

A loss of engine power due to oil starvation as a result of improper maintenance.

NTSB analysis

As the airplane climbed to an altitude of about 4,000 feet mean sea level after departure, the engine quit and would not restart. The pilot landed the airplane on a 3-lane section of highway; however, as the highway narrowed, the airplane’s left wing struck two road signs and was substantially damaged. On-scene personnel observed oil streaks on the left side of the airplane’s wing and fuselage that appeared to emanate from the engine cowl. Postaccident examination of the engine revealed that the No. 1 connecting rod bearing had seized and that internal engine damage was consistent with oil starvation. Additionally, examination revealed that a single propeller governor gasket was installed on the engine, whereas the proper gasket configuration was a governor pad plate sandwiched between two gaskets. Maintenance records showed that 10 hours before the accident, maintenance that required the removal and reinstallation of the propeller governor had been performed on the engine. The Mooney service manual does not specify that a 3-piece gasket stack be used when installing the propeller governor; however, the Mooney Illustrated Parts Manual shows a 3-piece gasket stack in place at the propeller governor. Additionally, a Lycoming Service Instruction and a Federal Aviation Administration Special Airworthiness Information Bulletin, both of which were issued in 2005, state that a propeller governor pad plate is necessary in this installation to eliminate the possibility of oil leakage between the propeller governor and the accessory housing.

Text from the NTSB. Open the NTSB docket for WPR12LA108 for the full record.