What was found
(CAN) WEB CRACKED HORIZONTALLY APPROX. 10 INCHES. CRACK COINCIDES WITH FLANGE OF UNDERLYING Z CHANNEL. PROBLEM APPEARS TO BE RELATED TO POOR MANUFACTURING PRACTICES. PRC SEALANT BEAD APPLIED TO Z CHANNEL FLANGE CURED BEFORE RIVETING. THE RESULT WAS THAT THE SEALANT BEAD CAUSED A STRESS RISER COMPOUNDED BY PRESSURIZATION LOADS ACCELERATING THE FATIGUE. THIS CONCLUSION WAS ARRIVED AT BY OBSERVING THAT THE CRACK EXACTLY CO-INSIDES WITH THE PATH OF THE SEALANT BEAD.