What was found
FS 409 & 128, RBL 18, INBD & OTBD VERTICAL POSTS HAVE INDICATIONS NOTED IN THE AFT FLANGE RADIUS AT WL 69, APPROX 0.250" LONG BY GREATER THAN 50% FSH. BOTH INDICATIONS FAILED NDT INSPECTION. REMOVED OVERBOARD EXHAUST VLV IAW QMM 21-24-34-000-401. INSTALLED SAME SERVICEABLE OVERBOARD EXHAUST VLV IAW AMM 21-24-34-400-801. INSTALLED SAME SERVICEABLE INSULATION AT FS 409+128, RBL 18 IAW AMM 25-81-01-400-801. LOCATED & DRILLED NEW SERVICEABLE FS 409+128 INBD & OTBD VERTICAL POST AT RBL 18 IAW SRM 51-409-11. INSTALLED NEW SERVICEABLE FS 40+128, RBL 18 VERTICAL POST IAW REO 601R-53-41-889 & SRM 51-42-06. FABRICATED NEW FS 409+128, RBL 18 INBD STIFFENER IAW EO 601R2208, SNIEO S18, DATD 11/0/15. PERFORMED OPERATIONS TEST OF THE OVERBOARD EXHAUST VLV IAW AMM 21-2-43-710-801. NO DEFECTS NOTED.