Narrative:

Aircraft was level at FL330, .74 mach on autoplt using VNAV and LNAV. At approximately XA00Z, captain returned to cockpit after using lavatory facilities. First officer was experiencing difficulty holding altitude. Tried using vertical speed control but was ineffective. Captain assumed control of aircraft and tried to level off aircraft using vertical speed -- still ineffective. Autoplt disengaged and aircraft flown manually to altitude, however, when electric trim was used, nothing happened. Circuit breakers were checked in. Manual stabilizer trim was tried next but trim wheel was jammed (could not trim nose down). System maintenance was contacted and with their guidance proceeded to troubleshoot system. Nothing seemed to work. 'Nose up' trim worked but once new position was reached could not trim 'nose down.' declared an emergency and diverted to preplanned alternate field (bna). All other suitable airports were experiencing heavy WX. Bna had the best WX and the longest runway. Proceeded to bna while still talking to maintenance and chicago dispatch to consider all options. Cabin crew notified of situation and were instructed to 'prep' the cabin for emergency landing and possible evacuate/evacuation. Upon descent into bna, aircraft was leveled at 6000 ft to do a ctlability check. Once flaps were extended to 10 degrees down and landing gear positioned down, lost all stabilizer trim (both nose up and nose down). Elevator control was adequate to conduct approach. 'Jammed stabilizer approach' emergency procedures were followed. A 15 degree flap landing was utilized. Extended straight-in approach was used. Landing was uneventful. Crash crew checked for hot brakes after exiting runway. No injuries or damage to the aircraft occurred. All crew members conducted themselves in a highly professional manner. Callback conversation with reporter revealed the following information: reporter captain confirmed aircraft type as B737-300. He had not received feedback from his company yet, but would get it. When talking with his company maintenance they mentioned something about a gear box and jackscrew probably causing the problem. As soon as they landed they were questioned by the FAA regarding the trim problem.

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Original NASA ASRS Text

Title: B737-300 ACFT IN CRUISE HAD DIFFICULTY WITH STABILIZER TRIM. EVEN ELECTRIC TRIM WOULD NOT CTL IT NOR MANUAL. FLC COULD NOT TRIM NOSE DOWN. AFTER COORD WITH COMPANY MAINT FLC DECLARED EMER AND DIVERTED. LNDG WAS UNEVENTFUL AND, THOUGH THE STABILIZER WAS COMPLETELY JAMMED, FLC HAD NO DIFFICULTY CTLING THE ACFT FOR APCH AND LNDG.

Narrative: ACFT WAS LEVEL AT FL330, .74 MACH ON AUTOPLT USING VNAV AND LNAV. AT APPROX XA00Z, CAPT RETURNED TO COCKPIT AFTER USING LAVATORY FACILITIES. FO WAS EXPERIENCING DIFFICULTY HOLDING ALT. TRIED USING VERT SPD CTL BUT WAS INEFFECTIVE. CAPT ASSUMED CTL OF ACFT AND TRIED TO LEVEL OFF ACFT USING VERT SPD -- STILL INEFFECTIVE. AUTOPLT DISENGAGED AND ACFT FLOWN MANUALLY TO ALT, HOWEVER, WHEN ELECTRIC TRIM WAS USED, NOTHING HAPPENED. CIRCUIT BREAKERS WERE CHKED IN. MANUAL STABILIZER TRIM WAS TRIED NEXT BUT TRIM WHEEL WAS JAMMED (COULD NOT TRIM NOSE DOWN). SYS MAINT WAS CONTACTED AND WITH THEIR GUIDANCE PROCEEDED TO TROUBLESHOOT SYS. NOTHING SEEMED TO WORK. 'NOSE UP' TRIM WORKED BUT ONCE NEW POS WAS REACHED COULD NOT TRIM 'NOSE DOWN.' DECLARED AN EMER AND DIVERTED TO PREPLANNED ALTERNATE FIELD (BNA). ALL OTHER SUITABLE ARPTS WERE EXPERIENCING HVY WX. BNA HAD THE BEST WX AND THE LONGEST RWY. PROCEEDED TO BNA WHILE STILL TALKING TO MAINT AND CHICAGO DISPATCH TO CONSIDER ALL OPTIONS. CABIN CREW NOTIFIED OF SIT AND WERE INSTRUCTED TO 'PREP' THE CABIN FOR EMER LNDG AND POSSIBLE EVAC. UPON DSCNT INTO BNA, ACFT WAS LEVELED AT 6000 FT TO DO A CTLABILITY CHK. ONCE FLAPS WERE EXTENDED TO 10 DEGS DOWN AND LNDG GEAR POSITIONED DOWN, LOST ALL STABILIZER TRIM (BOTH NOSE UP AND NOSE DOWN). ELEVATOR CTL WAS ADEQUATE TO CONDUCT APCH. 'JAMMED STABILIZER APCH' EMER PROCS WERE FOLLOWED. A 15 DEG FLAP LNDG WAS UTILIZED. EXTENDED STRAIGHT-IN APCH WAS USED. LNDG WAS UNEVENTFUL. CRASH CREW CHKED FOR HOT BRAKES AFTER EXITING RWY. NO INJURIES OR DAMAGE TO THE ACFT OCCURRED. ALL CREW MEMBERS CONDUCTED THEMSELVES IN A HIGHLY PROFESSIONAL MANNER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR CAPT CONFIRMED ACFT TYPE AS B737-300. HE HAD NOT RECEIVED FEEDBACK FROM HIS COMPANY YET, BUT WOULD GET IT. WHEN TALKING WITH HIS COMPANY MAINT THEY MENTIONED SOMETHING ABOUT A GEAR BOX AND JACKSCREW PROBABLY CAUSING THE PROB. AS SOON AS THEY LANDED THEY WERE QUESTIONED BY THE FAA REGARDING THE TRIM PROB.

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