What was found
DURING H CHECK IN MSP, MAINTENANCE WAS ACCOMPLISHING EO WORKCARD 5331-01297-02C (SB BD500-530010 ISSUE 004). DURING MODIFICATION, THE AFT CARGO DOOR SURROUND STRUCTURE C01343028- 103 LOWER SILL WAS FOUND WITH CORROSION. THE CORROSION FOUND IS ON THE OUTER SURFACE OF THE SILL LOCALLY AROUND THE FASTENER HOLES THAT ATTACH THE SCUFF PLATE. THIS ERA WILL REPAIR THE CORROSION. MX COMPLIED WITH ER/A 636421-14 PRI REV 0, ER/A 636421-14 PRI REV 1, ER/A 636421-14 PRI REV 2, ER/A 636421-14 PRI REV 3, ER/A 636421-14 PRI REV 4, ER/A 636421-14 PRI REV 5, AND ER/A 636421- 14 REV ORIG. ASSOCIATED ER/A 00-636421 ADDED FOR AC 8301. (LP# 1816272; AIRCRAFT WAS GROUNDED)