FLC OF AN LR31 EXPERIENCED AN ENG FAILURE DURING CRUISE AT FL470. AN EMER WAS DECLARED AND THE FLT DIVERTED. THE GARRETT ENG HAD BEEN SQUAWKED BY ANOTHER CREW PREVIOUSLY; AND HAD CHKED OUT SATISFACTORY DURING MAINT INSPECTION.

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WHILE ENRTE TO NEW FROM CLE; AT FL470 (APPROX 1 HR 45 MINS INTO FLT); A LOUD BANG WAS HEARD; FOLLOWED IMMEDIATELY BY THE ENG CHIP LIGHT; THE R OIL PRESSURE LOW LIGHT; AND SPOOL-DOWN OF THE R (#2) ENG. AN IMMEDIATE DSCNT WAS REQUESTED AND RECEIVED FROM ZME WHILE ENG WAS SECURED. ASKED CTR FOR CLOSEST SUITABLE ARPT(S); MEM WAS SUGGESTED. WE DECLARED AN EMER; COMPLETED ALL POH CHKLISTS FOR DSCNT; APCH AND LNDG. A NORMAL; UNEVENTFUL SINGLE ENG LNDG WAS ACCOMPLISHED IN MEM. THE ACFT HAD JUST COME OUT OF A 1200 HR INSPECTION. ANOTHER CREW HAD SQUAWKED ENG WHINE AND VIBRATION OF R ENG BEFORE INSPECTION; AND THE ACFT SENT TO INSPECTION EARLY BECAUSE OF THIS COMPLAINT. THE ENG WAS THOROUGHLY INSPECTED BY A MAINT FACILITY; BUT THEY COULD NOT FIND ANYTHING WRONG. BEFORE ENG FAILURE; PERFORMANCE; SOUND AND INDICATIONS OF ENG ALL APPEARED TO BE NORMAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: WHEN THE ENG WAS IN FOR EARLY INSPECTION; MAINT PERFORMED A SOAP TEST AND VIBRATION ANALYSIS AND FOUND NO DISCREPANCY. AFTER THE FLT DIVERT TO MEM; MAINT FOLLOW-UP REVEALED VISIBLE METAL AT THE OIL FILTER BYPASS. RPTR STATES THAT OUT OF ABOUT 2 CUPS OF OIL; 1/2 CUP WAS METAL. THE ENG WAS SENT TO GARRETT AND THE RPTR IS AWAITING THEIR FINAL ANALYSIS. THIS IS THE FIRST CATASTROPHIC FAIL OF THIS ENG IN 4 YRS. SUPPLEMENTAL INFO FROM ACN 357382: PRELIMINARY RPTS INDICATE A BEARING OR ACCESSORY GEAR DISINTEGRATED -- IMMEDIATELY COMPROMISED OIL AND OIL FILTER; AND SHUT DOWN THE ENG. ALL ATC ASSISTANCE WAS EXCELLENT AND THEY LEFT US ALONE AT APPROPRIATE TIMES SINCE THEY KNEW WE WERE EXTREMELY BUSY. PROPER TRAINING AND CREW COORD ALLOWED A POTENTIAL CATASTROPHIC FAILURE TO BE ROUTINELY HANDLED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THERE WERE NO UNUSUAL TEMPS; POWER LEVER SPLITS; ETC. THIS FO WAS SURPRISED BECAUSE HE ALWAYS HEARD THAT ENG FAILS ONLY OCCURRED DURING A PWR CHANGE -- THIS HAPPENED WITHOUT ANY CREW INPUT. THIS ACFT IS EQUIPPED WITH GARRETT TFE731-2-3B ENGS.