A B737-800 climbing through 6000 ft declared an emergency and returned to airport due to loss of all...

Attributes
ACN	617266
Time
Date	200405
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 6000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : zzz.tracon
Operator	common carrier : air carrier
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude climbout : takeoff climbout : initial
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	617266
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : landed in emergency condition flight crew : declared emergency other
Consequence	other other Other
Factors
Maintenance	performance deficiency : fault isolation performance deficiency : repair performance deficiency : logbook entry
Supplementary
Problem Areas	Maintenance Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

Stabilizer trim went inoperative climbing through about 6000 ft MSL. There was a previous write up on this. While attempting to manual trim as first officer was getting out a checklist for this abnormality, aircraft 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 control. Although speed was selected to approximate when event began, aircraft continued to accelerate and exacerbate pitch controllability problems. Disconnected autothrottles to manually control speed. Requested block altitude from ATC while control wheel force was being dealt with. Manual trim attempted again, and aircraft began trimming in wrong direction again (about two wheel rotations and stop). Significant force now necessary to maintain pitch control. Accomplished memory items for runaway trim and declared an emergency and returned to ZZZ. Landed with flaps fifteen to minimize need for pitch trim changes. Landing uneventful. Assessed event after landing and advised tower emergency was over. Taxi in uneventful. Callback conversation with reporter revealed the following information: the reporter stated all the control functions of the stabilizer were failed, autoplt, yoke switches and manual trim. The reporter said when manual trim was attempted the wheel trimmed in the wrong direction and stopped. The reporter stated the autothrottle was disconnected due to speed buildup and adding to the pitch problems. The reporter said the manual trim was again tried and again trimmed in the wrong direction (two wheel rotations and stop). The reporter stated forward pressure on the yoke was required to maintain pitch control. The reporter said when on the ground maintenance could duplicate the problem and could not trim the stabilizer in any mode. The reporter said in talking to maintenance a few days later it was reported the airplane had a catastrophic failure of the stabilizer trim system. The reporter stated every electrical and mechanical component in the pitch trim system was replaced before the airplane was returned to service.

Original NASA ASRS Text

Title: 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.

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.

A B737-800 climbing through 6000 ft declared an emergency and returned to airport due to loss of all pitch trim control, autoplt, yoke switches and manual.