Cessna P210N N34VF accident near Farmington, Pennsylvania

Probable cause

A total loss of engine power due to fatigue failure of the crankshaft drive gear teeth.

NTSB analysis

During cruise flight in instrument meteorological conditions, the engine lost total power and the commercial pilot performed a forced landing to a field after emerging from the clouds about 300 ft above ground level; the airplane struck trees and a power line, resulting in a loss of control, impact with the ground, and subsequent post-impact fire.

Examination of the engine revealed that the crankshaft drive gear was missing teeth, the camshaft gears were damaged, and each of the six pistons displayed valve impact damage. It is likely that the missing teeth from the drive gear caused an out-of-alignment condition that led to a cascade of additional damage to the mating timing gear on the camshaft. The improper engagement of the crankshaft drive gear to the camshaft compromised the timing of the entire valvetrain, which resulted in the loss of engine power.

Review of the five most recent oil analysis results conducted during the 13 months before the accident revealed elevated levels of iron, chromium, silicon and nickel; elements present in the alloy steel drive gear. These levels were considered elevated relative to the initial oil analysis sample taken about 15 months before the accident. It is likely that the fatigue cracking had begun or become severe enough to alter the composition of the oil; however, there were no material anomalies or significant findings to indicate the gear was deficient. In addition, there were no irregularities discovered with the maintenance history, tolerances, or timing that would preclude eventual failure of the gear, therefore, no definitive cause of the gear failure could be determined.

Text from the NTSB. Open the NTSB docket for ERA18LA072 for the full record.