B737-300 crew had altitude excursion after the autoplt cruise trim did not keep the stabilizer in a ...

Attributes
ACN	520097
Time
Date	200108
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : ave.vortac
State Reference	CA
Altitude	msl bound lower : 29000 msl bound upper : 29400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla.artcc tower : dca.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	520097
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	atc equipment other atc equipment : radar aircraft equipment other aircraft equipment : stab out of trim light illuminated other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued alert flight crew : returned to assigned altitude none taken : detected after the fact other
Consequence	other other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Stabilizer trim failure. In cruise flight with 'a' autoplt engaged the 'stabilizer out of trim' light illuminated. While getting out the QRH a quick check of the instruments showed our altitude at 29400 ft and climbing. I held the yoke firmly and disconnected the autoplt and began to correct the altitude. This all occurred while we were accelerating to 310 KTS indicated as assigned by ATC. As we were descending back to FL290 the center controller asked us our altitude. We told him we were at 29400 ft and correcting back to FL290. We continued the flight manually.

Original NASA ASRS Text

Title: B737-300 CREW HAD ALT EXCURSION AFTER THE AUTOPLT CRUISE TRIM DID NOT KEEP THE STABILIZER IN A 'TRIMMED' CONDITION.

Narrative: STABILIZER TRIM FAILURE. IN CRUISE FLT WITH 'A' AUTOPLT ENGAGED THE 'STABILIZER OUT OF TRIM' LIGHT ILLUMINATED. WHILE GETTING OUT THE QRH A QUICK CHK OF THE INSTS SHOWED OUR ALT AT 29400 FT AND CLBING. I HELD THE YOKE FIRMLY AND DISCONNECTED THE AUTOPLT AND BEGAN TO CORRECT THE ALT. THIS ALL OCCURRED WHILE WE WERE ACCELERATING TO 310 KTS INDICATED AS ASSIGNED BY ATC. AS WE WERE DSNDING BACK TO FL290 THE CTR CTLR ASKED US OUR ALT. WE TOLD HIM WE WERE AT 29400 FT AND CORRECTING BACK TO FL290. WE CONTINUED THE FLT MANUALLY.

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.

B737-300 crew had altitude excursion after the autoplt cruise trim did not keep the stabilizer in a 'trimmed' condition.