A B737-300; DURING DSCNT; CREW NOTED STABILIZER TRIM WHEEL JERKING WITH ABNORMAL NOISE. TRIM WHEEL JAMMED ELECTRICALLY AND MANUALLY. CAUSED BY FAILING TRIM WHEEL BEARINGS.

Narrative

DURING DSCNT NOTICED STABILIZER TRIM WHEEL JERKING AND MAKING UNUSUAL NOISE DURING AUTOPLT TRIMMING. DISENGAGED AUTOPLT AND USED ELECTRIC TRIM TO ACTIVATE TRIM. AS TRIM WHEEL TURNED; IT SOUNDED DIFFERENT THAN NORMAL. REENGAGED AUTOPLT AND CONTINUED DSCNT. AS WE STARTED OUR SPD REDUCTION TO 250 KTS AT 10000 FT; STABILIZER WHEEL AGAIN BEGAN TO BIND AS AUTOPLT TRIM MOTOR TRIED TO TRIM ACFT. AGAIN; AUTOPLT WAS DISENGAGED; CYCLED MAIN ELECTRIC/AUTOPLT TRIM CUT OUT SWITCHES AND STABILIZER TRIM OVERRIDE SWITCH. DECIDED TO FLY ACFT WITHOUT AUTOPLT AND USED MAIN ELECTRIC TRIM. TRIM WHEEL WOULD TURN; BUT STILL SOUNDED AS IF SOMETHING WAS BINDING. THEN TURNING VECTORS TO ARPT; STABILIZER WHEEL JAMMED AND WOULD NOT TRIM ELECTRICALLY OR MANUALLY. AS ACFT WAS SLOWED TO 220 KTS; FLAPS 5 DEGS WAS SELECTED. AT THIS POINT; TRIM WHEEL RESUMED NORMAL OP. VISUAL APCH WITHOUT AUTOPLT FLOWN TO NORMAL LNDG. THE POINT IS THAT THERE EXISTED A MALFUNCTION WHICH HAS NO SPECIFIC NON-NORMAL CHKLIST THAT APPLIES. SUBSEQUENT MAINT ACTION REVEALED THAT THE BEARINGS ON THE STABILIZER WHEEL TRIM MECHANISM HAD OR WERE IN THE PROCESS OF FAILURE.