What was found
DURING HEAVY CHECK MAINTENANCE FOUND CORROSION, AFT FUSELAGE INTERNAL SKIN AT WASTE BOX FRAME 88-89 STRINGER 28R. REMOVED AND REPLACE AFT FUSELAGE INTERNAL SKIN DOUBLER AT WASTE BOX BETWEEN FRAME 88-89 STRINGER 28R PER SRM 51-40-08, RESTORED SURFACE PROTECTION TO INTERNAL AND EXTERNAL FASTENERS PER SRM 51-23-04, 51-23-05, 51-23-06. A/C REMAINS IN CHECK.