A PRATT & WHITNEY JT8D COMPRESSOR DISK WAS IMPROPERLY REWORKED DURING ENG OVERHAUL CAUSING CATASTROPHIC AND UNCONTAINED ENG FAILURE.

Narrative

PART WAS REPAIRED PER MAINT MANUAL AND PROPER AR WAS USED. PART FAILED; THUS ENG FAILED. SOME PARTS OF MAINT MANUAL HAVE BEEN ALTERED IN MY SHOP FOR YRS AND NOW BECAUSE OF THIS INCIDENT; THINGS WILL CHANGE TO THE PROPER METHODS. MY STAMP WAS USED BY ME FOR THE REPAIR AND I WAS QUESTIONED BY THE FAA AND NTSB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR RELATED THE FOLLOWING INFO ABOUT THE FAILURE OF THE JT8D COMPRESSOR DISK WHICH WAS PLATED IN HIS SHOP. HE SAID THE DISK WAS CADMIUM PLATED BUT WAS NOT NICKEL PLATED PER THE APPROVED REPAIR PROCS. THE ERROR HE SUSPECTS WAS CAUSED BY THE MECH TRAINEE ASSIGNED TO HIM WHO WAS NOT FAMILIAR WITH THE PLATING SHOP PROCS. HE STATED THAT AFTER REVIEW OF THE APPROVED REPAIR PROCS AND THE MAINT MANUAL REPAIR PROCS IT WAS DISCOVERED THERE WAS NO AFTER PLATING CHK OR MEASUREMENT OF THE AMOUNT OF METAL DEPOSITED ON THE DISK. THE RPTR SAID THE CORRECT AMOUNT OF PLATING WAS .0002 INCHES TO .0004 INCHES. HE RELATED THAT IN 12 YRS DOING THIS WORK FOR 2 AIRLINES NO ONE HAS EVER MEASURED THE PLATING THICKNESS. THE RPTR SAID THE FAA AND THE NTSB HAVE CONTACTED AND INTERVIEWED HIM ABOUT THIS INCIDENT.