A B737-300 in descent at 14000 ft the autoplt began a climb to 14300 ft and was switched off, reengaged and began climb again. Switched off after altitude deviation.

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Attributes
ACN	478563
Time
Date	200007
Day	Sat
Local Time Of Day	1201 To 1800
Place
State Reference	DE
Altitude	msl single value : 14000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc.artcc tower : rdu.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 122 flight time total : 7678 flight time type : 540
ASRS Report	478563
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	non adherence : published procedure non adherence : far
Independent Detector	aircraft equipment : altitude alert other flight crewa
Resolutory Action	flight crew : returned to original clearance
Consequence	other other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

We were cleared to descend to 14000 ft. Just prior to leveloff, ATC said to return to normal speed (320 KIAS) from the 250 KIAS restr. Instead of continuing to descend, the aircraft started to climb. As the PNF, I was busy doing other duties and didn't notice the climb, but saw the altitude flashing light. By the time we were approximately 14300 ft. I made a comment and after no action by the captain, I disconnected the autoplt and manually descended to 14000 ft. The captain assumed control as the PF and re-engaged the #1 autoplt. It once again started to climb. Both altimeters were verified to be set correctly. The autoplt was once again disengaged. The next attempt was successful. Whatever the mechanical/electrical problem was, the problem was a failure to monitor the situation by both pilots and to take action before the altitude deviation exceeded allowable limits. This was the last leg of a 2 day trip, returning to base, fatigue and complacency are at a high level.

Original NASA ASRS Text

Title: A B737-300 IN DSCNT AT 14000 FT THE AUTOPLT BEGAN A CLB TO 14300 FT AND WAS SWITCHED OFF, REENGAGED AND BEGAN CLB AGAIN. SWITCHED OFF AFTER ALTDEV.

Narrative: WE WERE CLRED TO DSND TO 14000 FT. JUST PRIOR TO LEVELOFF, ATC SAID TO RETURN TO NORMAL SPD (320 KIAS) FROM THE 250 KIAS RESTR. INSTEAD OF CONTINUING TO DSND, THE ACFT STARTED TO CLB. AS THE PNF, I WAS BUSY DOING OTHER DUTIES AND DIDN'T NOTICE THE CLB, BUT SAW THE ALT FLASHING LIGHT. BY THE TIME WE WERE APPROX 14300 FT. I MADE A COMMENT AND AFTER NO ACTION BY THE CAPT, I DISCONNECTED THE AUTOPLT AND MANUALLY DSNDED TO 14000 FT. THE CAPT ASSUMED CTL AS THE PF AND RE-ENGAGED THE #1 AUTOPLT. IT ONCE AGAIN STARTED TO CLB. BOTH ALTIMETERS WERE VERIFIED TO BE SET CORRECTLY. THE AUTOPLT WAS ONCE AGAIN DISENGAGED. THE NEXT ATTEMPT WAS SUCCESSFUL. WHATEVER THE MECHANICAL/ELECTRICAL PROB WAS, THE PROB WAS A FAILURE TO MONITOR THE SIT BY BOTH PLTS AND TO TAKE ACTION BEFORE THE ALTDEV EXCEEDED ALLOWABLE LIMITS. THIS WAS THE LAST LEG OF A 2 DAY TRIP, RETURNING TO BASE, FATIGUE AND COMPLACENCY ARE AT A HIGH LEVEL.

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.