What was found
PILOT REPORTED VIBRATION IN FLIGHT 1800 RPM. ON LANDING ROLL OUT PILOT SMELLED WOOD SMOKE. VISUAL INSPECTION OF PROPELLER AND HUB FOUND SOOT ESCAPING FROM BEHIND FORWARD CRUSH PLATE AND HUB BOLTS FINGER TIGHT. REMOVAL OF FRONT CRUSH PLATE FOUND 3 OF 8 BOLTS MISSING BOLT HEADS. VISUAL INSPECTION OF SEPARATED END OF BOLT SHOWS GRANULAR STRUCTURE CONSISTENT WITH HYDROGEN EMBRITTLEMENT. DAMAGE TO ONE BLADE OF PROP FACE CONSISTENT WITH A METAL OBJECT, LIKE A SEPARATED BOLT HEAD, STRIKING THE PROP. REMOVAL OF PROPELLER AND HUB SHOWED CHARRING OF THE PROPELLER BETWEEN THE HUB AND CRUSH PLATES. MT233R1506AJ