What was found
WHILE COMPLYING WITH SB 31 METHOD 1 (INSTALLING INSPECTION PANELS) AND AD 02-26-02, FOUND LEFT INBOARD WALK BOX RIB AFT ANGLE SUPPORT COMPROMISED WITH SEVERE EXFOLIATION DAMAGE. THE ORIGINAL PIECE WAS IN A BAY COATED WITH DIRT. THE AIRCRAFT HAD BEEN STORED WITH WINGS OFF FOR 7 YEARS AND NO DEFECTS WERE NOTED WHILE LOOKING IN THE WING CENTER SECTION PRIOR TO ASSEMBLY. SINCE A BOROSCOPE HAS LIMITED ABILITY, I RECOMEND INSTALLING THE PANELS TO ALLOW REMOVAL OF DIRT AND OTHER DEBRIS THAT ACCUMULATES OVER TIME. MANUFACTURED AN ANGLE ALUMINUM BRACE FROM STANDARD ANGLE ALUMINUM TO REPLACE ORIGINAL PART.