What was found
DURING BASIC CHECK, CORROSION DAMAGE WAS DISCOVERED DURING INSPECTION ON THE CENTER FUSELAGE III WASTE BOX SKIN DOUBLER, P/N 170-66931-001, ALONG THE INNER EDGES OF THE DOUBLER (REFERENCE PHOTO 1 FOR DETAILS). THE CORROSION DAMAGE WAS BLENDED WITH THE DEEPEST POST-BLENDOUT AREA MEASURING APPROXIMATELY 2.561 INCHES X 0.842 INCHES TO A MAXIMUM DEPTH OF 0.029 INCHES. THREE BLENDED AREAS EXCEED THE ALLOWABLE DAMAGE LIMITS PROVIDED IN SRM PART II 53-23-60/AD01. THIS EO IS BEING ISSUED TO PROVIDE INSTRUCTIONS TO ACCOMPLISH THE PERMANENT REPAIR OF THE CORRODED CENTER FUSELAGE III WASTE BOX SKIN DOUBLER, P/N 170-66931-001, BY REMOVING AND REPLACING THE CORRODED PART. PART REPLACEMENT WILL BE ACCOMPLISHED IN ACCORDANCE WITH THE DRAWINGS LISTED IN TABLE 2 AND SRM CHAPTER 51 STANDARD PRACTICES. SUPPLEMENTAL FOLLOW-ON INSPECTIONS ARE NOT REQUIRED FOR DIRECT REPLACEMENT OF THE CENTER FUSELAGE III WASTE BOX SKIN DOUBLER. BECAUSE THE CENTER FUSELAGE III WASTE BOX SKIN DOUBLER IS A PSE, ACCOMPLISHMENT OF THIS EO HAS BEEN CLASSIFIED BY ENGINEERING AS A MAJOR REPAIR DUE TO THE COMPLEXITY OF ITS REPLACEMENT. EO E175-53MR-447 IS BEING ACCOMPLISHED BY WO 2719873.