Mooney Aircraft Corp. M20K N231GZ accident near Addison, Texas

Probable cause

The fatigue failure of the engine’s camshaft gear teeth which resulted in a loss of all engine power. Contributing to the accident was the non-compliance with the engine manufacturer’s recommended service bulletin.

NTSB analysis

The airplane lost all engine power during a precision instrument approach for landing to the destination airport. After the pilot was unsuccessful in attempting to restart the engine, he performed an off-airport landing to a road, during which the airplane struck a pole and a postcrash fire ensued. There was substantial damage to the wings and fuselage.

Postaccident examination revealed that about 12 of the camshaft gear teeth were fractured due to fatigue cracking. The airplane engine’s camshaft gear part numbers were affected by the engine manufacturer’s service bulletin (SB) for camshaft gear tooth fracture or cracks of the teeth. The SB called for the replacement of the camshaft gear with a newer model. The intent of the SB was to eliminate the possibility of camshaft gear tooth fracture, resulting in power loss or in-flight shutdown; compliance with the SB is not mandatory for Part 91 operations. Based upon the camshaft gear part numbers, the SB was not complied with but likely would have addressed the fatigue failure of the camshaft gear teeth.

The maintenance records for the airplane were destroyed in the postimpact fire and could not be examined.

Text from the NTSB. Open the NTSB docket for CEN23LA062 for the full record.