As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AC WAS IN FOR HEAVY CHECK FOUND CENTER FUSELAGE 3 PASSENGER CABIN FLOOR STRUCTURE CORROSION FOUND AT LONGITIDINAL BEAM FR 87 AND RBL 12" AREA. AAR MX REMOVED AND REPLACED PN 170-65669-004 LONGITIDINAL BEAM FR 87 AND RBL 12" AREA IAW SRM 51-41-01, 51-42-03, 51-43-03.