What was found
ENGINE FAILED WHILE AC WAS ON GROUND. UPON DISASSEMBLY OF ENGINE, FOUND GAS PRODUCER ROTOR TIE BOLT BROKEN IN HALF. FURTHER EXAMINATION FOUND THAT NR 2 NOZZLE, WHICH HAD BEEN OVERHAULED 1751 HOURS PRIOR, WAS MISSING 3 OF 5 KEYS THAT HOLD DIAPHRAGM IN PLACE. INSPECTION OF WELDS ON THE 2 REMAINING KEYS FOUND THAT THEY WERE NOT WELDED ON 3 SIDES, AS IS REQUIRED. THE WELDS APPEARED TO LACK PENETRATION. THE AREAS WHERE THE MISSING 3 KEYS WERE ATTACHED ALSO HAD EVIDENCE OF WELDS THAT DID NOT MEET THE REQUIREMENTS. IT IS BELIEVED THAT THE FAILURE OF THE WELDS AND THE SUBSEQUENT LOSS OF THE KEYS AND SHIFTING OF THE DIAPHRAGM RESULTED IN CONTACT OF THE DIAPHRAGM WITH THE ROTOR AND EVENTUALLY FAILURE OF TIE BOLT.