The flight instructor reported that, after takeoff on the instructional flight, the Aerostar M20’s engine was running smoothly before it “missed” or “hesitated.”
He initiated a return to the airport, but shortly after the engine began to make loud noises and vibrate, ultimately experiencing a total loss of power.
The flight instructor performed a forced landing to a field near Clever, Missouri, resulting in substantial damage to the airplane and serious injuries to the flight instructor and student.
Examination of the engine revealed that the No. 2 connecting rod had failed. Remnants of the connecting rod bearing found within the oil pan exhibited evidence of bearing failure and extrusion.
Due to the extensive secondary engine damage, the reason for the failure of the No. 2 bearing could not be determined.
The engine was overhauled 11 years, six months before the accident, and had accumulated about 16 hours of flight time in the preceding three years.
Guidance published by the engine manufacturer stated that abnormal wear could occur during engine start due to a loss of protective oil film after an extended period of inactivity and recommended that all engines not in continuous service be overhauled every 12 years.
Probable cause: The failure of the engine No. 2 connecting rod bearing for reasons that could not be determined due to the extensive secondary engine damage.
NTSB Identification: CEN17LA110
This February 2017 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.