A B737-800 CLBING THROUGH 6000 FT DECLARED AN EMER AND RETURNED TO ARPT DUE TO LOSS OF ALL PITCH TRIM CTL; AUTOPLT; YOKE SWITCHES AND MANUAL.

Narrative

STABILIZER TRIM WENT INOPERATIVE CLBING THROUGH ABOUT 6000 FT MSL. THERE WAS A PREVIOUS WRITE UP ON THIS. WHILE ATTEMPTING TO MANUAL TRIM AS FO WAS GETTING OUT A CHKLIST FOR THIS ABNORMALITY; ACFT BEGAN TRIMMING ON ITS OWN (ABOUT TWO WHEEL ROTATIONS AND STOP) IN WRONG DIRECTION CAUSING A NEED FOR MODERATE FORWARD YOKE PRESSURE TO MAINTAIN PITCH CTL. ALTHOUGH SPD WAS SELECTED TO APPROXIMATE WHEN EVENT BEGAN; ACFT CONTINUED TO ACCELERATE AND EXACERBATE PITCH CONTROLLABILITY PROBS. DISCONNECTED AUTOTHROTTLES TO MANUALLY CTL SPD. REQUESTED BLOCK ALT FROM ATC WHILE CTL WHEEL FORCE WAS BEING DEALT WITH. MANUAL TRIM ATTEMPTED AGAIN; AND ACFT BEGAN TRIMMING IN WRONG DIRECTION AGAIN (ABOUT TWO WHEEL ROTATIONS AND STOP). SIGNIFICANT FORCE NOW NECESSARY TO MAINTAIN PITCH CTL. ACCOMPLISHED MEMORY ITEMS FOR RUNAWAY TRIM AND DECLARED AN EMER AND RETURNED TO ZZZ. LANDED WITH FLAPS FIFTEEN TO MINIMIZE NEED FOR PITCH TRIM CHANGES. LNDG UNEVENTFUL. ASSESSED EVENT AFTER LNDG AND ADVISED TWR EMER WAS OVER. TAXI IN UNEVENTFUL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED ALL THE CTL FUNCTIONS OF THE STABILIZER WERE FAILED; AUTOPLT; YOKE SWITCHES AND MANUAL TRIM. THE RPTR SAID WHEN MANUAL TRIM WAS ATTEMPTED THE WHEEL TRIMMED IN THE WRONG DIRECTION AND STOPPED. THE RPTR STATED THE AUTOTHROTTLE WAS DISCONNECTED DUE TO SPEED BUILDUP AND ADDING TO THE PITCH PROBS. THE RPTR SAID THE MANUAL TRIM WAS AGAIN TRIED AND AGAIN TRIMMED IN THE WRONG DIRECTION (TWO WHEEL ROTATIONS AND STOP). THE RPTR STATED FORWARD PRESSURE ON THE YOKE WAS REQUIRED TO MAINTAIN PITCH CTL. THE RPTR SAID WHEN ON THE GND MAINT COULD DUPLICATE THE PROB AND COULD NOT TRIM THE STABILIZER IN ANY MODE. THE RPTR SAID IN TALKING TO MAINT A FEW DAYS LATER IT WAS RPTED THE AIRPLANE HAD A CATASTROPHIC FAILURE OF THE STABILIZER TRIM SYS. THE RPTR STATED EVERY ELECTRICAL AND MECHANICAL COMPONENT IN THE PITCH TRIM SYS WAS REPLACED BEFORE THE AIRPLANE WAS RETURNED TO SVC.