A be-400's aileron trim malfunctioned and caused an uncommanded roll while descending through 18;000...

Narrative:

We were descending out of 18000 ft on our approach when my first officer noticed that we had a yellow box on the pfd (it was an a) as I was looking up the squawk in the checklist. I noticed that we were off course by 45 degrees and the plane kept turning to the right. I told the first officer to disengage the autopilot and hand fly back on course. We then noticed that the right roll trim had runaway and my first officer hit the trim interrupt button and kept it depressed. I went to the checklist and read the roll trim emergency checklist. I selected the right trim motor and tried to retrim with success. I declared an emergency with ATC and told them our problem along with how many souls and fuel we had on board. They vectored us around and we landed with no further incident. The fire crash crews met our plane as we rolled to a stop. We then taxied back to the FBO. This airplane had a similar incident 30 days prior to this event. I was told by maintenance on the ground that a golf cart had damaged the right roll trim section of the plane and was released by maintenance. It looks like this plane needs a whole new right roll trim replaced.

Original NASA ASRS Text

Title: A BE-400's aileron trim malfunctioned and caused an uncommanded roll while descending through 18;000 FT on approach with the A autopilot engaged. An emergency was declared; while the crew overrode the malfunction with the normal trim switch.

Narrative: We were descending out of 18000 FT on our approach when my First Officer noticed that we had a yellow box on the PFD (it was an A) as I was looking up the squawk in the checklist. I noticed that we were off course by 45 degrees and the plane kept turning to the right. I told the First Officer to disengage the autopilot and hand fly back on course. We then noticed that the right roll trim had runaway and my First Officer hit the trim interrupt button and kept it depressed. I went to the checklist and read the roll trim emergency checklist. I selected the right trim motor and tried to retrim with success. I declared an emergency with ATC and told them our problem along with how many souls and fuel we had on board. They vectored us around and we landed with no further incident. The fire crash crews met our plane as we rolled to a stop. We then taxied back to the FBO. This airplane had a similar incident 30 days prior to this event. I was told by maintenance on the ground that a golf cart had damaged the right roll trim section of the plane and was released by maintenance. It looks like this plane needs a whole new right roll trim replaced.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	837125
Time
Date	200905
Local Time Of Day	1201-1800
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Beechjet 400
Operating Under FAR Part	Part 91
Flight Phase	Descent
Flight Plan	IFR
Component
Aircraft Component	Aileron Tab
Person 1
Function	Pilot Not Flying Captain
Person 2
Function	Approach Pilot Flying First Officer
Events
Anomaly	Aircraft Equipment Problem Critical Ground Event / Encounter Loss Of Aircraft Control

A be-400's aileron trim malfunctioned and caused an uncommanded roll while descending through 18;000 ft on approach with the a autopilot engaged. An emergency was declared; while the crew overrode the malfunction with the normal trim switch.