What was found
CRACKING OCCURRED IN A SHORT TIME SPAN, DURING NORMAL OPERATION. CRACKS WERE OVER AN AREA APPROX 7 INCHES X 7 INCHES. ONE PIECE APPROX 3 INCHES X 3 INCHES SEPARATED FROM THE PART. AFTER CRACKING, DEFORMATION OF LOWER TRAILING EDGE OCCURRED BECAUSE IT WAS NO LONGER RIGID. IF THIS PROBLEM HAD GONE UNNOTICED, HEAT DAMAGE WOULD PROBABLY HAVE OCCURRED TO ADJACENT PARTS. MATERIAL OR MFG PROCESS COULD BE SUSPECT. RECENT MFG BULLETIN CAB 07-2 AFFECTS SOME PRIMARY EXHAUST DUCTS DUE TO IMPROPER MFG, BUT IT DOES NOT APPLY TO THIS ONE. (MFG HAS BEEN MADE AWARE OF THIS PROBLEM, PART WAS RETURNED TO THEM ON REQUEST FOR EVALUATION). (K)