LTT HAS INADVERTENT ENG FEATHER ON DSCNT TO LAND.

Narrative

WE WERE AT OUR CRUISE ALT OF 9000 FT; JUST PRIOR TO BEGINNING OUR DSCNT. AS THE PF; I CALLED FOR THE DSCNT CHK AND WE HEARD A 'BANG' AND THE ACFT YAWED L. THE AUTOPLT WAS ENGAGED AT THE TIME AND I DISENGAGED IT AND BEGAN TO HAND FLY. THE CAPT DETERMINED THAT WE HAD A PARTIAL ENG FAILURE. WHEN I LOOKED AT THE INSTS; THE R ENG WAS NORMAL (63 PERCENT TORQUE; 85 PERCENT NP) AND THE L ENG WAS HIGHER TORQUE (AROUND 100 PERCENT) AND NP 39 PERCENT. THE CAPT BROUGHT THE THROTTLE BACK; THEN FORWARD; AND BACK AGAIN WITH NO APPARENT EFFECT ON CTLING THE ENG. THE ENG WAS DEFINITELY OPERATING; BUT WAS APPARENTLY FEATHERED. WE DECLARED AN EMER AND WERE CLRED FOR A VISUAL TO RWY 27. WE CONTINUED TO FLY DOWNWIND AND PERFORMED THE PRECAUTIONARY SHUTDOWN PROC AND REVIEWED THE SINGLE ENG GAR. WE THEN TURNED INTO THE ARPT AND LANDED UNEVENTFULLY. WE TAXIED TO THE GATE; DEPLANED THE PAX AND REVIEWED THE EVENTS. THE AUTOFEATHER WAS UNARMED AND THE L ENG ELECTRIC FEATHER SWITCH HAD BEEN ACTIVATED. THE CAPT COULD NOT REMEMBER ACTIVATING EITHER SWITCH AND ASKED ME IF I HAD; WHICH I HAD NOT. THE SWITCH POS COULD HAVE BEEN SELECTED AS PART OF THE PRECAUTIONARY ENG SHUTDOWN PROC. THE CAPT; HOWEVER; THINKS THAT HE MAY HAVE ACCIDENTLY ACTIVATED THE ELECTRIC FEATHER PUMP INSTEAD OF ARMING THE AUTOFEATHER (THEY ARE ABOVE EACH OTHER ON THE OVERHEAD PANEL) WHEN I CALLED FOR THE DSCNT CHK. I CANNOT VERIFY THAT THIS IS WHAT HAPPENED; BUT IT IS A POSSIBILITY. HOWEVER; THE ELECTRIC FEATHER SWITCH IS A GUARDED SWITCH TO PREVENT SUCH AN OCCURRENCE. IF THIS IS THE CASE; KNOWING THAT HUMAN ERROR IS SUCH A SIGNIFICANT FACTOR IN MANY INCIDENTS AND ACCIDENTS; IT IS IMPERATIVE THAT EACH OF US TAKE MORE TIME TO INSURE WE'RE ACTIVATING THE CORRECT SWITCH AND CONTINUE TO IMPROVE COCKPIT DESIGNS SO AS TO PREVENT INCIDENTS SUCH AS THIS ONE.