BE58 pilot cruising at 9;000 ft reports runaway trim; resulting in a 700 foot altitude loss and a 90...

Narrative:

I left [before sun rise] and was flying for about an hour when I had a runaway trim. The auto pilot was out in the airplane and deferred per the MEL and I was therefore having to hand fly the airplane. I was using mainly manual trim throughout the flight fine tuning the airplane. I decided to use the electric trim and I noticed that it was sticking and so I stopped using it. I reached over to get something off of the seat next to me and I looked back and noticed I was in a dive. The electric trim was running down and the nose dropped. I tried to disconnect the trim with the red disconnect button but it didn't work. I then searched for the circuit breaker. In the time it took for me to find the breaker and try to continue to fly I lost 700 feet and turned just over 90 degrees. I immediately climbed back up and turned back on course. ATC asked me 'so are you heading back to ZZZ?' I told them no and said that I had a trim problem and I thought it was the attitude indicator too but I thought about it and it was just the trim and me turning while looking down in the airplane. I suggest that I keep my eyes outside if it is VMC like it was therefore I wouldn't have turned as much. Also if I had known exactly where the circuit breaker was for the trim then it wouldn't have taken as long to get it offline.

Original NASA ASRS Text

Title: BE58 pilot cruising at 9;000 FT reports runaway trim; resulting in a 700 foot altitude loss and a 90 degree turn before the electric trim circuit breaker can be located and pulled. The autopilot was not being used at the time.

Narrative: I left [before sun rise] and was flying for about an hour when I had a runaway trim. The auto pilot was out in the airplane and deferred per the MEL and I was therefore having to hand fly the airplane. I was using mainly manual trim throughout the flight fine tuning the airplane. I decided to use the electric trim and I noticed that it was sticking and so I stopped using it. I reached over to get something off of the seat next to me and I looked back and noticed I was in a dive. The electric trim was running down and the nose dropped. I tried to disconnect the trim with the red disconnect button but it didn't work. I then searched for the circuit breaker. In the time it took for me to find the breaker and try to continue to fly I lost 700 feet and turned just over 90 degrees. I immediately climbed back up and turned back on course. ATC asked me 'So are you heading back to ZZZ?' I told them no and said that I had a trim problem and I thought it was the attitude indicator too but I thought about it and it was just the trim and me turning while looking down in the airplane. I suggest that I keep my eyes outside if it is VMC like it was therefore I wouldn't have turned as much. Also if I had known exactly where the circuit breaker was for the trim then it wouldn't have taken as long to get it offline.

Data retrieved from NASA's ASRS site as of July 2013 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	1063943
Time
Date	201301
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	Baron 58/58TC
Operating Under FAR Part	Part 135
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Elevator Trim System
Person 1
Function	Pilot Flying
Qualification	Flight Crew Commercial
Events
Anomaly	Aircraft Equipment Problem Critical Inflight Event / Encounter Loss Of Aircraft Control

BE58 pilot cruising at 9;000 ft reports runaway trim; resulting in a 700 foot altitude loss and a 90 degree turn before the electric trim circuit breaker can be located and pulled. The autopilot was not being used at the time.