What was found
PERFORMED A PHASE 2, 3, & D, TASK A361004, BLEED AIR LINE EXHIBITED CORROSION WHERE ITS FLANGE FASTENS TO THE FUSELAGE SKIN BS 187.87 RBL 27, AND WL 62.79. ON DISASSEMBLY, FLANGE TO FUSELAGE JOINT FOUND WITH HEAVY DISSIMILAR METAL CORROSION. INVESTIGATION FOUND THAT DURING A PRIOR MX EVENT, DUCT INSTALLED WITHOUT GASKET. INSTALLER UTILIZED RED RTV SEALANT. ACFT UNDERWENT A PHASE 2, 3, 4, 5, & 6 12 MONTHS AND .5 FLIGHT HOUR PRIOR TO THIS DISCOVERY.