THE STABILIZER WAS JAMMED FULL FORWARD; PROCS WERE ACCOMPLISHED; FUEL WAS DUMPED; EMER LNDG WAS MADE AT THE CLOSEST SUITABLE ARPT.

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DEPARTING BOSTON ON THE LOGAN 9 DEP WE EXPERIENCED RUNAWAY TRIM. WENT THROUGH EMER PROCS (CAPT AND SO) WHILE I FLEW THE ACFT. ACFT DID NOT RESPOND WELL TO BOTH TRIM MOTORS BEING DISCONNECTED. DECLARED EMER AND FLEW TO NEAREST SUITABLE ARPT (SYR). DUMPED APPROX 9000 LBS FUEL ENRTE. LANDED AT SYR NON-EVENTFULLY WITH EMER EQUIP STANDING BY. I FELT THERE WAS EXCELLENT CREW COORD BTWN THE 3 COCKPIT CREW MEMBERS AND THE CABIN FLT ATTENDANTS. COCKPIT RESOURCE MGMNT TRAINING HELPFUL IN THIS INCIDENT. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING INFO: THIS EVENT WAS MORE A JAMMED FULL FORWARD STABILIZER THAN A RUNAWAY TRIM. THE RUNAWAY TRIM PROC INVOLVES SHUTTING OFF BOTH ELECTRIC TRIM MOTORS. HOWEVER; THE CRUISE TRIM MOTOR PWR WAS NOT INTERRUPTED WHEN THE CIRCUIT BREAKER WAS PULLED AND CONTINUED TO DRIVE THE TRIM TO THE FULL FORWARD POS. WHEN THE MANUAL TRIM WAS USED TO ROLL NOSE UP IT TOOK A GREAT DEAL OF FORCE AND THEN; UNLESS THE PLT STRAIGHT ARM LOCKED THE TRIM FROM MOVING; IT WOULD RUN BACK TO THE FULL FORWARD POS. IT TOOK ABOUT 50 LBS OF FORCE TO HOLD THE CTL COLUMN TO OPPOSE THE OUT OF TRIM CONDITION. BY THE 2 PLTS DISTRIBUTING THEIR EFFORTS TO LOCK THE YOKE BACK WHILE THEY DUMPED THE FUEL AND PREPARED THE CABIN FOR THE POSSIBILITY OF LOSING CTL OF THE ACFT IN THE LNDG; THEY WERE ABLE TO WRESTLE THE ACFT ON THE ACTIVITIES NECESSARY TO MAKING A SAFE LNDG. MAINT FOUND SOME CORRODED TERMINALS IN THE E AND E COMPARTMENT AND WENT THROUGH WITH A MAJOR OVERHAUL OF THE WHOLE ELEVATOR SYS. AN EXISTING WRITE UP WAS A 'MISSING CURTAIN' BTWN THE HORIZ STABILIZER AND THE ELEVATOR. THE ACFT HAD SAT OVERNIGHT AT BOSTON IN HVY RAIN BEFORE THE FLT THE NEXT MORNING WITH THAT CURTAIN MISSING. THE CURTAIN IS ON THE CDL EQUIP LIST. SUPPLEMENTAL INFO FROM ACN 292356: THE CAPT AND FO DISPLAYED AMAZING AIRMANSHIP AND SAVED THE LIVES OF ALL ABOARD.