What was found
AFT CARGO DOOR THRESHOLD HAS CORROSION, 3" FROM EDGE OF DOOR EDGE. GROUNDED - YES. BLENDED OUT DAMAGE AT AFT CARGO DOOR THRESHOLD. ORIGINAL MATERIAL THICKNESS IS .050, MATERIAL REMOVED IS .010, REMAINING MAT IS .040 FOUND TO BE OUT OF LIMITS IAW B737-900ER SRM 53-60-15-1A-1 AND B737-900ER SRM 53-60-15-01-1. REMOVED AND INSTALLED A NEW AFT CARGO DOOR THRESHOLD PN# 146A8123U6 PO:0 IAW BOEING DWG# 146A8120 REV A AND B737-900ER SRM 51-40-02 AND BOEING DWG #146A8340 REV-.