NTSB Identification: CEN13LA370
14 CFR Part 91: General Aviation
Accident occurred Tuesday, June 25, 2013 in El Reno, OK
Probable Cause Approval Date: 10/27/2014
Aircraft: MOONEY M20J, registration: N205MC
Injuries: 2 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The pilot stated that the engine abruptly lost power while he was practicing instrument approaches under visual flight rules. His efforts to restore engine power were unsuccessful. The pilot subsequently executed a forced landing to the center median of a roadway. A postaccident examination revealed that the dual magneto assembly was not functioning properly. Although the magneto drive shaft operated during engine crankshaft rotation, the magneto points did not open as required. A teardown examination revealed that the magneto components were worn. In addition, the threaded inserts had lifted out of the mounting block. The magneto assembly was inspected less than 1 flight hour before the accident during an engine propeller strike inspection, and the magneto block, points, and cam were replaced at that time. The accident flight was the second flight since the inspection and maintenance work had been performed. Although the magneto points might have been misaligned due to the threaded insert lifting out of the mounting block, it is unlikely that such a discrepancy would have resulted in a loss of magneto function within such a short timeframe. The magneto failure caused the loss of engine power; however, the cause of the magneto failure could not be determined.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A loss of engine power, which resulted from the failure of the magneto assembly for reasons that could not be determined during postaccident examinations.
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