What was found
EXTERIOR FUSELAGE SKIN BS.360 TO 500E STR.0 HAS SIGNS OF CORROSION AROUND BELLY DRAINS (9EA.CIRCLED). GROUNDED - YES. REMOVED CORROSION FROM 9(EACH) LOCATIONS IAW B737-900 ER SRM 51-10-02, ORIG THICKNESS .063 IAW B737-900 ER SRM 53-30-01, LOWEST READINGS AT STA'S 500B AND 500E REMOVED .003 REMAINING MAT .060 FOUND TO BE IN LIMITS IAW B737-900 ER SRM 53-00-01. REINSTALLED DRAIN PLUGS IAW B737-900ER AMM 51-41-13. TOOL #T8927K CAL DUE 27/SEP/24. THIS IS A CAT B REPAIR REINSPECT REQUIRED 50,000 FLIGHT CYCLES FROM AIRPLANE DELIVERY PER B737-900ER SRM 53-30-01-1A-1 TABLE 103 SUBMITTED TO ENGINEERING FOR TRAX THIS CLOSES THE DEFECT.