Date: 201311
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Aircraft: Beechjet 400
Operator: Fractional
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class E ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Aileron Trim System
Component problem: Malfunctioning
Reporter organization: Fractional
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; Flight Crew Overcame Equipment Problem; General Declared Emergency
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: During climbout at approximately 15;000 FT MSL the aircraft suffered a roll trim runaway. First Officer was flying with the autopilot engaged. I had been scanning outside for traffic and upon glancing back into the cockpit noticed the control yoke turned about 20 degrees to the right. Asking the obvious I said; 'Why is the yoke turned this way' as I first looked to the inclinometer to see if the rudder had somehow gotten way out of trim. It looked good; and we both looked down at the roll trim to see it had moved significantly away from the neutral position to a wing up deflection. It still appeared to be moving; so I immediately pushed and held the Trim Interrupt/Autopilot Disengage Switch. Without discussion I then became the flying pilot. I commend my First Officer for not missing a beat in switching rolls as I was simply the first to realize the problem and perform the memory item. We told ATC that we wanted to level off at 15;000 FT to work on a little problem we had. He asked if we wanted to stay in the area as we worked it out and we agreed. He issued us vectors. First Officer brought out the Emergency Checklist for a trim runaway and we proceeded to work our way through it. After deselecting the 'Both' position of the roll trim and selecting the 'left' side; the runaway stopped and I was then able to use the left side trim to overcome the opposing force of the opposite side runaway. With the aircraft back under more normal control we advised ATC of our condition; declared an emergency and requested vectors back. As I was still hand flying; I had my First Officer step to the back and brief our passenger of our need to return. As we were in normal control of the aircraft and it would be a normal visual approach and landing; we felt there was no need to brief the passenger on brace position; evacuation; etc. She was most concerned on the delay this would cause her evening. The flight continued without further incident to a landing. We deplaned our passenger; contacted company and Maintenance. Another crew was called and the passenger was on her way in a different aircraft about 2 hours later than originally scheduled.




Synopsis: BE400 Captain experiences runaway aileron trim climbing through 15;000 FT. With the left aileron trim active and the right trim off; trim returns to normal; but the crew elects to return to the departure airport.