A SAAB 340B IN CRUISE AT 14000 FT DECLARED AN EMER AND DIVERTED DUE TO #1 ENG PROP GEAR BOX CASE FAILURE.

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ON THE EVENING OF DEC/XA/00; I FLEW AS CAPT ON A SAAB 340B ON A PART 121 SCHEDULED ACR FLT FROM LOS ANGELES; CA; TO XXX; US. AT APPROX XA15 LCL TIME; WHILE LEVEL AT 14000 FT MSL; 15 MI N OF PASO ROBLES ARPT; WE (THE CREW AND PAX) HEARD A LOUD SOLID THUD OR POP. THE ACFT YAWED SLIGHTLY TO THE L AND THEN CORRECTED BACK TO THE R VIA THE AUTOPLT; WHICH WAS ENGAGED AT THE TIME. SECONDS LATER THE L ENG OIL PRESSURE LIGHT ON THE CENTRAL WARNING PANEL ILLUMINATED ALONG WITH THE MASTER WARNING LIGHTS AND TRIPLE STROKE CHIME. UPON SCANNING THE INSTS; I CAN RECALL ONLY THAT THE L TORQUE GAUGE WAS BTWN 0% AND 15%. AFTER RETARDING THE L CONDITION LEVER TO FUEL 'OFF;' THE L PROP FAILED TO FEATHER. THE L PROP PUMP WAS PLACED IN THE MANUAL FEATHER POS; PER THE MEMORY ITEMS. THE PROP APPEARED TO CHANGE PITCH BUT STILL DID NOT FEATHER. I FOUND THIS PERPLEXING AND FELT THAT WE MUST HAVE MISSED A STEP OR PERFORMED A MEMORY ITEM OUT OF SEQUENCE; AS THE PROP SHOULD HAVE FEATHERED AT THIS POINT. SOMETIME DURING THE EMER CHKS; ATC ISSUED US A DSCNT CLRNC. WE DECLARED AN EMER AND ADVISED HIM THAT WE HAD LOST AN ENG. HE ASKED WHAT OUR INTENTIONS WERE. WE REQUESTED OUR DISTANCE FROM THE NEAREST ARPT. ATC ADVISED US THAT WE WERE 15 MI N OF PASO ROBLES. WE REQUESTED CURRENT WX CONDITIONS. AS ATC READ BACK CURRENT WX CONDITIONS AT BOTH PRB AND MRY; I RETRIEVED THE PRB APCH PLATES FROM MY BINDER; AS WE WERE UNFAMILIAR WITH THE PRB ARPT. ATC AGAIN ASKED OUR INTENTIONS. WE ADVISED HIM THAT WE WOULD LIKE TO DIVERT TO PRB. WE ALSO REQUESTED THAT EMER EQUIP BE STANDING BY. WE WERE ISSUED A DSCNT CLRNC TO 8000 FT AND A L TURN; VECTORS FOR A VOR/DME APCH TO PRB. WE COMPLIED WITH THE CLRNC. I SELECTED 1/2 BANK ON THE AUTOPLT CTL PANEL; AS WE WOULD BE TURNING INTO THE DEAD ENG. DURING THE TURN; WE RECEIVED AN AILERON INDICATION ON THE EADI. ATC ASKED IF WE WOULD LIKE THE VOR-B APCH INSTEAD. I QUICKLY REVIEWED THE APCH AND WE ADVISED ATC THAT WE COULD ACCEPT THE VOR-B APCH. WE WERE THEN CLRED FOR THE VOR-B APCH. WHILE FLYING OUTBOUND FROM THE VOR; THE R ENG ANTI-ICE WAS TURNED ON. WE DSNDED INTO THE OVCST LAYER AND PERFORMED THE PROC TURN IN IMC. ONCE ESTABLISHED ON THE FINAL APCH COURSE; THE FO ACTIVATED THE PLT CTLED LIGHTING ON THE ARPT. DURING THE CIRCLING MANEUVER; WE WERE ABLE TO COMPLETE THE BEFORE LNDG CHKS AND LANDED SUCCESSFULLY. IT IS MY BEST ESTIMATE THAT THE ENTIRE INCIDENT; FROM THE TIME OF FAILURE TO LNDG; TOOK APPROX 10-15 MINS. THE PAX WERE DEPLANED. THERE WERE NO INJURIES TO ANY OF THE PAX OR CREW MEMBERS. UPON EXITING THE ACFT; NO STRUCTURAL DAMAGE WAS EVIDENT. THE L ENG COWLING WAS COVERED WITH OIL; AND OIL WAS PUDDLING BELOW THE ENG. I ALSO NOTED THAT THE PROP GEAR BOX OIL SITE GAUGE CONTAINED NO OIL. HRS LATER; AFTER MAINT ARRIVED AND REMOVED THE UPPER ENG COWLING; A LARGE HOLE (APPROX 1 INCH WIDE BY 6 INCHES LONG) COULD BE SEEN IN THE LOWER PORTION OF THE PROP GEAR BOX CASING; AS WELL AS SEVERAL PIECES OF METAL DEBRIS LYING IN THE LOWER ENG COWLING. IT WAS APPARENT THAT SOMETHING HAD COME APART INSIDE THE PROP GEAR BOX AND WAS EJECTED OUT OF THE CASING. I SUSPECT THAT THE INTERNAL DAMAGE TO THE PROP GEAR BOX AND LOSS OF OIL WERE THE REASON THAT WE WERE UNABLE TO FEATHER THE PROP.