What was found
THE NR 1 RT SLAT FILLET FAIRING DEPARTED AIRCRAFT ON DEPARTURE. NO ABNORMAL INDICATIONS WERE NOTED IN COCKPIT. MAINTENANCE VERIFIED THE NR 1 RT SLAT FILLET FAIRING WAS MISSING. THE FAIRING WAS RECOVERED ON THE RUNWAY IN FCO. ALSO, FOUND DAMAGE TO THE NR 1 RT SLAT. THE NR 1 RT SLAT WAS REMOVED AND REPLACED, THE MISSING SLAT FAIRING WAS REPLACED. *S/D* INVESTIGATION REVEALED THAT A .375 FASTENER HAD FAILED SOMETIME IN THE PAST DUE TO STRESS CORROSION AND THE FILLET WAS BEING HELD IN PLACE WITH THE 3 REMAINING FASTENERS. AN FCD WAS ISSUED TO INSPECT THE FILLET FAIRING INSTALLATION FOR INTEGRITY ON ALL AFFECTED DC-10 AIRCRAFT.