What was found
INSP MX RUN-UP, VIBRATION NR 2 PROP ASSY, VIBRATED A FEW SEC THEN DIMINISHED. DISCOVERED 2 SAFETY WIRED BOLTS HEADS ON GROUND THAT SNAPPED OFF PROP ASSY. SPINNER HAD PUNCTURE DAMAGE, MINOR DAMAGE TO 2 PROP BLADES. SPINNER REMOVED, 2 LOCK WIRED BOLTS HAD SHEARED OFF FROM BLADE CLAMP & START LOCK PLATE ASSY. FOD INSPEC DISCOVERED LOCK PLATE 75 YDS FROM ACFT. NR 2 ENG REPLACED DUE TO SOAP RECOMMENDATION. NR 2 PROPELLER HAD BEEN R&R. PROPELLER BALANCING TASK COMPLETED PRIOR TO INCIDENT. START LOCK PLATE WEAR AT START LOCK CONTACT POINT. START LOCK PN 830 ROTATED PAST CONTACT SURFACE OF START LOCK PLATE (PN A-3495). FORCE APPLIED TO START LOCK PLATE CAUSED 2 ATTACHING BOLTS (A-2016) TO SHEAR.