As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE IN FLIGHT, THE C50462 SPINNER MOUNTING PLATES FAILED, RELEASING THE SPINNER FROM THE AIRCRAFT. THE PROPELLER BECAME LOOSE ON THE CRANKSHAFT DUE TO THE MISSING PLATES. WAS DAMAGED BEYOND REPAIR DUE TO SEVERE FRETTING. A NUMBER OF THE ATTACHING STUDS WERE SKIPPED AS WERE THE CRANKSHAFT BUSHINGS FROM THE SEVERE ABNORMAL LOADS IMPOSED UPON THEM. COMMON TO FIND THE C50462 PLATES CRACKED DURING OVERHAUL OR MINOR REPAIRS. HOWEVER, THIS IS FIRST OF IN-FLIGHT FAILURE KNOWN.