What was found
ENGINE NR 3 EXPERIENCED A SLOW INCREASE IN VIBRATION FROM 105 TO 218 UNITS IN 3 MINUTES WITH A OR B SELECTED. ALL OTHER PARAMETERS NORMAL. INSPECT MASTER AND INTERNAL GEARBOX CHIP DETECTORS AND OIL FILTERS, NO EVIDENCE OF ENGINE FAILURE NOTED. ACOMPLISHED BOROSCOPE INSPECTION , NO DEFECTS NOTED. REMOVED, CLEANED, LUBRICATED AND RE-INSTALLED FAN BLADES. FOUND DAMAGE FAN ATRITTION LINER, REPAIR LINER IAW RB211 MM 72-31-01. ACCOMPLISHED VIBRATION SURVEY IAW RR MM 71-00-00, FOUND NORMAL. AIRCRAFT RETURN TO SERVICE.