The private pilot reported that, 10 miles from the destination airport, the passengers heard a loud “clank” and smoke entered the Cessna 210’s cockpit.
Shortly after, the engine experienced a total loss of power and the propeller stopped turning.
The pilot selected a field near Bryan, Texas, as a forced landing site, but the plane hit trees and terrain at the edge of the field.
The pilot and passengers were able to extricate themselves through the right side passenger window.
A post-accident engine examination revealed a catastrophic failure of the engine crankshaft between the No. 2 main bearing journal and the No. 2 connecting rod journal.
The damage displayed on the No. 2 bearing was consistent with the bearing having shifted and spun.
Several of the bearing supports displayed fretting near the through-bolt holes.
An accurate measurement of the pre-accident through-bolt torques could not be determined due to the loads subjected upon the crankcase when the crankshaft failed.
Review of maintenance records indicated that the through bolts were properly torqued during the remanufacturing process nearly 1,000 flight hours before the accident and that there was no record of major work performed on the engine since that time. However, the wear signatures displayed on the bearing supports indicated that the crankcase halves were shifting in a manner consistent with improper torque of the through bolts.
Probable cause: A failure of the crankshaft due to improper torque of the crankcase through bolts.
NTSB Identification: CEN16LA107
This February 2016 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.