What was found
CARRY-THRU CRACKS, REWORKED TO B-401-5 TO MEET REQUIREMENTS OF AD 82-16-08. TOTAL TIME ON THE CARRY THRU IS UNKNOWN. WHILE PERFORMING A 100HR INSPECTION, CRACKS WERE FOUND RADIATING FROM CUT-OUT FOR UPPER WING ATTACH BOLTS ON BOTH SIDES OF CARRY-THRU. 2 LONGEST CRACKS APPROXIMATELY .25 INCH IN LENGTH & ARE VISIBLE ON BOTH INSIDE & OUTSIDE OF TUBE. THERE IS A SECOND SMALLER CRACK AT EACH CUT-OUT. 2 LARGEST CRACKS ARE IN SAME PLACE IN EACH CUT OUT. THEY ALIGN WITH A PART OF THE CENTERING TOOL USED TO TIGHTEN THE UPPER WING ATTACH BOLT. IF IMPROPER TECHNIQUE USED WITH THIS TOOL IT COULD POSSIBLY CAUSE THESE 2 CRACKS. THERE ARE NO TOOL MARKS ON THE CARRY THRU THAT WOULD INDICATE THAT THIS IS THE CAUSE.