Narrative:

Enroute to fat from sfo we were abeam modesto at 7000'. Suddenly the right propeller went into feather mode with 300-400 RPM showing on the propeller gauge with 4100 ft- pounds of torque and an itt of approximately 550 degree C. Along with the above the blue fine pitch light illuminated and stayed operation. Realizing we now had a serious problem developing I declared an emergency with castle approach control and advised them that we were now going to make an emergency landing at modesto. As I proceeded with those tasks I advised the F/a to prepare the cabin for an emergency landing at mod and I asked the first officer to brief the passenger that one of the engines had developed a problem and that we were making precautionary landing at mod. Now as I stated before, the propeller RPM range was 300-400 RPM. The engine was running fine with good oil pressure and temperature. The torque on that engine had risen to 4100 for about 10 seconds before I brought back its power lever in order to reduce it. I believed this to be a propeller malfunction of some type. (Feathered with blue fine light on). I asked the first officer to look at the emergency check lists and find the list for propeller feathered in flight. He (first officer) then advised us that there was nothing for feather in-flight, only propeller overspd and propeller fluctuating. Not having too much time left as we were now at this point on base leg to ASR at mod, I called for the propeller fluctuating check list in order to attempt regain of control of the propeller. Since this attempt did not work and the check list called for engine shutdown when safety permits. I decided to do so. This occurred at approximately 1200-1500 AGL. As we were turning final at mod and being cleared to land we finished the descent check list and before landing check we shut down and secured the right engine. Completing the 500' check we proceeded with an uneventful landing in mod. I believed this to be a propeller malfunction. After talking with company it was brought to my attention that in the event of propeller feather in flight one item to try is the automatic feather circuit breakers. However this check list appears as a phase ii item under engine failure checklists, we did not do this because we did not feel there was a problem with the engine only a problem with the propeller. I would like to recommend that this item be included as separate list or it should be referred to that part of the engine failure check list. As it turned out a sensor had broken off the propeller governing control system allowing it to proceed into feather mode.

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Original NASA ASRS Text

Title: EQUIPMENT MALFUNCTION. UNWANTED PROPELLER FEATHER. EMERGENCY LNDG.

Narrative: ENROUTE TO FAT FROM SFO WE WERE ABEAM MODESTO AT 7000'. SUDDENLY THE RIGHT PROP WENT INTO FEATHER MODE WITH 300-400 RPM SHOWING ON THE PROPELLER GAUGE WITH 4100 FT- LBS OF TORQUE AND AN ITT OF APPROX 550 DEG C. ALONG WITH THE ABOVE THE BLUE FINE PITCH LIGHT ILLUMINATED AND STAYED OP. REALIZING WE NOW HAD A SERIOUS PROBLEM DEVELOPING I DECLARED AN EMER WITH CASTLE APCH CTL AND ADVISED THEM THAT WE WERE NOW GOING TO MAKE AN EMER LNDG AT MODESTO. AS I PROCEEDED WITH THOSE TASKS I ADVISED THE F/A TO PREPARE THE CABIN FOR AN EMER LNDG AT MOD AND I ASKED THE F/O TO BRIEF THE PAX THAT ONE OF THE ENGINES HAD DEVELOPED A PROBLEM AND THAT WE WERE MAKING PRECAUTIONARY LNDG AT MOD. NOW AS I STATED BEFORE, THE PROP RPM RANGE WAS 300-400 RPM. THE ENGINE WAS RUNNING FINE WITH GOOD OIL PRESSURE AND TEMP. THE TORQUE ON THAT ENGINE HAD RISEN TO 4100 FOR ABOUT 10 SECONDS BEFORE I BROUGHT BACK ITS POWER LEVER IN ORDER TO REDUCE IT. I BELIEVED THIS TO BE A PROP MALFUNCTION OF SOME TYPE. (FEATHERED WITH BLUE FINE LIGHT ON). I ASKED THE F/O TO LOOK AT THE EMER CHECK LISTS AND FIND THE LIST FOR PROP FEATHERED IN FLIGHT. HE (F/O) THEN ADVISED US THAT THERE WAS NOTHING FOR FEATHER INFLT, ONLY PROP OVERSPD AND PROP FLUCTUATING. NOT HAVING TOO MUCH TIME LEFT AS WE WERE NOW AT THIS POINT ON BASE LEG TO ASR AT MOD, I CALLED FOR THE PROP FLUCTUATING CHECK LIST IN ORDER TO ATTEMPT REGAIN OF CONTROL OF THE PROP. SINCE THIS ATTEMPT DID NOT WORK AND THE CHECK LIST CALLED FOR ENGINE SHUTDOWN WHEN SAFETY PERMITS. I DECIDED TO DO SO. THIS OCCURRED AT APPROX 1200-1500 AGL. AS WE WERE TURNING FINAL AT MOD AND BEING CLRED TO LAND WE FINISHED THE DESCENT CHECK LIST AND BEFORE LNDG CHECK WE SHUT DOWN AND SECURED THE RIGHT ENGINE. COMPLETING THE 500' CHECK WE PROCEEDED WITH AN UNEVENTFUL LNDG IN MOD. I BELIEVED THIS TO BE A PROP MALFUNCTION. AFTER TALKING WITH COMPANY IT WAS BROUGHT TO MY ATTN THAT IN THE EVENT OF PROP FEATHER IN FLT ONE ITEM TO TRY IS THE AUTO FEATHER CIRCUIT BREAKERS. HOWEVER THIS CHECK LIST APPEARS AS A PHASE II ITEM UNDER ENGINE FAILURE CHECKLISTS, WE DID NOT DO THIS BECAUSE WE DID NOT FEEL THERE WAS A PROBLEM WITH THE ENGINE ONLY A PROBLEM WITH THE PROP. I WOULD LIKE TO RECOMMEND THAT THIS ITEM BE INCLUDED AS SEPARATE LIST OR IT SHOULD BE REFERRED TO THAT PART OF THE ENGINE FAILURE CHECK LIST. AS IT TURNED OUT A SENSOR HAD BROKEN OFF THE PROP GOVERNING CONTROL SYSTEM ALLOWING IT TO PROCEED INTO FEATHER MODE.

Data retrieved from NASA's ASRS site as of August 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.