What was found
WHILE PERFORMING A 3 YEAR INSPECTION OF THE WING CENTER SECTION IAW AD, NOTE: 2002-26-02 AND MFG SB NR 31, THE FORWARD UPPER SPAR CAPSTRIP, PN 415-13027 WAS FOUND TO HAVE AN AREA OF INTERGRANULAR (IG) CORROSION NEAR THE UPPER WING ATTACH FITTING. THE CORROSION WAS BARELY VISIBLE WITH THE WING CENTER SECTION INSTALLED ON THE AIRCRAFT. THE FULL EXTENT OF THE IG CORROSION WAS NOT KNOWN TILL THE WING CENTER SECTION SPAR WAS REMOVED FROM THE AIRCRAFT, STRIPPED OF PAINT AND THOROUGHLY CLEANED. INITIALLY THE AREA OF CORROSION APPEARED TO LOOK LIKE PEALING PAINT. CLOSER INSPECTION REVEALED AN AREA .6250 WIDE X 6 INCHES LONG X .1875 INCH DEEP. RECOMMEND A CLOSE AND THOROUGH INSPECTION OF WING CENTER INSPECTION FOR