What was found
AFT LOWER FUSELAGE OB RT 6 INCHES AFT OF VHF ANTENNA HAS THREE CRACKS IN AN AREA 4 INCHES LONG. *S/D* CRACKS CONFIRMED TO BE BETWEEN .25 TO .38 INCHES LONG EACH. CAUSE CONFIRMED AS CORROSION INTERNALLY IN FUSELAGE SKIN AT FAYING SURFACE OF S-28R AND AT ADJACENT INTERCOSTAL. PORTIONS OF S-28R BETWEEN BS 1050 AND 1070 ALSO CORRODED. STRINGER REPAIRED PER SRM 53-10-3, SKIN REPAIRED PER SRM 53-30-3.