Hartzell HCD4N3A Propeller system—bearing failed. SDR 510022648 (photo above)
Half inch diameter ball from bearing discovered failed during propeller overhaul. There were no indications or warnings except potentially metal particles in the expelled grease during propeller servicing at aircraft phase checks, although it is unknown how long the bearing has been in this condition. Probable cause is manufacturing flaw. Damage to adjacent parts will be inspected and replace as necessary, all ball bearings are replaced at overhaul as part of the mandatory replacement parts contained in the overhaul kit. P/No: B6144. TSN: 2726 hours/72 months TSO: 2726 hours/72 months.