What was found
DURING HEAVY CHECK MAINTENANCE FOUND CORROSION, AFT FUSELAGE INTERNAL AFT INTERCOSTAL AT WATER DRAIN FRAME 86-87 STRINGER 28R. REMVED AND REPLACED AFT INTERCOSTAL AT WATER DRAIN FRAME 86-87 STRINGER 28R PER SRM 51-40-08, RESTORED SURFASCE PROTECTION TO FASTENERS PER SRM 51-23-06. A/C REMAINS IN CHECK.