Narrative:

On the evening of dec/xa/00, I flew as captain on a saab 340B on a part 121 scheduled air carrier flight from los angeles, ca, to XXX, us. At approximately XA15 local time, while level at 14000 ft MSL, 15 mi north of paso robles airport, we (the crew and passenger) heard a loud solid thud or pop. The aircraft yawed slightly to the left and then corrected back to the right via the autoplt, which was engaged at the time. Seconds later the left engine oil pressure light on the central warning panel illuminated along with the master warning lights and triple stroke chime. Upon scanning the instruments, I can recall only that the left torque gauge was between 0% and 15%. After retarding the left condition lever to fuel 'off,' the left propeller failed to feather. The left propeller pump was placed in the manual feather position, per the memory items. The propeller 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 propeller should have feathered at this point. Sometime during the emergency checks, ATC issued us a descent clearance. We declared an emergency and advised him that we had lost an engine. He asked what our intentions were. We requested our distance from the nearest airport. ATC advised us that we were 15 mi north of paso robles. We requested current WX conditions. As ATC read back current WX conditions at both prb and mry, I retrieved the prb approach plates from my binder, as we were unfamiliar with the prb airport. ATC again asked our intentions. We advised him that we would like to divert to prb. We also requested that emergency equipment be standing by. We were issued a descent clearance to 8000 ft and a left turn, vectors for a VOR/DME approach to prb. We complied with the clearance. I selected 1/2 bank on the autoplt control panel, as we would be turning into the dead engine. During the turn, we received an aileron indication on the eadi. ATC asked if we would like the VOR-B approach instead. I quickly reviewed the approach and we advised ATC that we could accept the VOR-B approach. We were then cleared for the VOR-B approach. While flying outbound from the VOR, the right engine anti-ice was turned on. We descended into the overcast layer and performed the procedure turn in IMC. Once established on the final approach course, the first officer activated the pilot controled lighting on the airport. During the circling maneuver, we were able to complete the before landing checks and landed successfully. It is my best estimate that the entire incident, from the time of failure to landing, took approximately 10-15 mins. The passenger were deplaned. There were no injuries to any of the passenger or crew members. Upon exiting the aircraft, no structural damage was evident. The left engine cowling was covered with oil, and oil was puddling below the engine. I also noted that the propeller gear box oil site gauge contained no oil. Hours later, after maintenance arrived and removed the upper engine cowling, a large hole (approximately 1 inch wide by 6 inches long) could be seen in the lower portion of the propeller gear box casing, as well as several pieces of metal debris lying in the lower engine cowling. It was apparent that something had come apart inside the propeller gear box and was ejected out of the casing. I suspect that the internal damage to the propeller gear box and loss of oil were the reason that we were unable to feather the propeller.

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Original NASA ASRS Text

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

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.