MD80 altitude deviation caused by autoplt trim pitching over.

Attributes
ACN	627742
Time
Date	200408
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : sea.airport
State Reference	WA
Altitude	msl single value : 10000
Environment
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	MD-83
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	627742
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : auto pilot trim lite
Resolutory Action	flight crew : returned to assigned altitude flight crew : regained aircraft control flight crew : overrode automation
Consequence	other
Factors
Maintenance	performance deficiency : logbook entry
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

On arrival at 10000 ft, we received a 210 KT speed. We slowed and turned to a 160 degree heading. The autoplt trim light came on, and the nose started to drop rapidly. We disconnected the autoplt and with considerable force, arrested the descent and returned to 10000 ft. No comment from ATC. Event entered in aircraft logbook.

Original NASA ASRS Text

Title: MD80 ALTDEV CAUSED BY AUTOPLT TRIM PITCHING OVER.

Narrative: ON ARR AT 10000 FT, WE RECEIVED A 210 KT SPD. WE SLOWED AND TURNED TO A 160 DEG HDG. THE AUTOPLT TRIM LIGHT CAME ON, AND THE NOSE STARTED TO DROP RAPIDLY. WE DISCONNECTED THE AUTOPLT AND WITH CONSIDERABLE FORCE, ARRESTED THE DSCNT AND RETURNED TO 10000 FT. NO COMMENT FROM ATC. EVENT ENTERED IN ACFT LOGBOOK.

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.