Cessna P210N N732FU accident near Bryan, Texas

Probable cause

A failure of the crankshaft due to improper torque of the crankcase through bolts.

NTSB analysis

The private pilot reported that, 10 miles from the destination airport, the passengers heard a loud "clank" and smoke entered the cockpit. Shortly thereafter, the engine experienced a total loss of power and the propeller stopped turning. The pilot selected a field as a forced landing site, but the airplane impacted 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 postaccident 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 preaccident 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.

Text from the NTSB. Open the NTSB docket for CEN16LA107 for the full record.