Narrative:

We departed ZZZ to ZZZ1. While first officer (pm) was checking in with center and performing his after takeoff duties; I noticed an abnormal forward force required to keep the nose at a normal ascent angle; and the stab trim was not responding to my inputs. However; there were no cautions or aurals. I stopped accelerating at 200 KIAS; but kept a normal climb rate going to achieve higher altitude to work on the problem. Climbing past approximately 10000 ft; I wanted to check to see if either of the disconnect switches was the cause of the inactive stab trim. I disconnected the stab trim using the left stab disconnect switch and had the first officer run the stab trim caution QRH to follow a logical sequence of events to reset it and possibly help with the problem. We ended up resetting stab/mach trim; and we were back to where we were before I disconnected. At one point in the remaining climb I requested autopilot engagement; but turned it off again shortly thereafter because I was not comfortable with the amount of potential back force that would occur if the autopilot disconnected automatically. I did hold for the approximately 3 seconds that it was engaged. We were now level at 18000 ft where we had requested to remain in order to begin the communications portion of our problem solving (maintenance; dispatch; flight attendant; passengers; etc). It was then that I noticed the trim was above 9; but it was static. I don't know when or how in the sequence of events it got there; but I had not noticed any additional control forces beyond what I had been inputting. Furthermore; there had been no aural and no caution of any kind. After a few seconds; the numerical trim meter went nose up by .2 (one standard increment) and stopped there. Shortly after; we saw that it went up another .2; and that's when I first noticed a further increase in required force and immediately called for the stab trim runaway immediate action items and the QRH checklist. By the time we disconnected; the trim had reached 10 nose up and remained there for the rest of the flight (the indicator went blank when the circuit breakers were pulled; but the mechanic who met us in ZZZ2 said that it was still at 10 when we were parked at the gate). We had declared an emergency with center who told us that ZZZ3 was about 5 miles away. I was not comfortable spiraling down from 18000 ft with that controllability issue; so we were offered and accepted ZZZZ; approximately 40 miles to our northeast. We descended and then slowed per the QRH; which helped the controllability; especially after flaps were extended to 8 degrees to set up for a flaps 20 landing. The first officer advised the flight attendants and the passengers as we were setting up for the visual approach at ZZZ2. ATC put us on a 10 mile final and had emergency equipment waiting for us. The landing was uneventful besides a higher-than-normal approach and landing speed; and we taxied off the runway and to the gate followed by the emergency vehicles.callback conversation with reporter revealed the following info: the reporter stated that his air carrier's maintenance personnel determined that a trim switch caused the system to fail; but that report is questionable because the trim did not operate from either pilot's yoke control switch. The normal trim setting for a heavily loaded aircraft is about 8 units of nose up trim. This aircraft's trim failed after the takeoff trim was set and then ultimately drifted to about 10 units requiring a force estimated to be about 50 pounds to keep it in level flight. The force would have been considerably higher had the aircraft been accelerated above a slow maneuvering speed.

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Original NASA ASRS Text

Title: A CRJ-200 flight crew experienced runaway elevator trim failure after takeoff. Continuous trim movement was controlled by following the QRH Runaway Stabilizer Trim checklist. An emergency was declared followed by a diversion to a nearby airport.

Narrative: We departed ZZZ to ZZZ1. While First Officer (PM) was checking in with center and performing his after takeoff duties; I noticed an abnormal forward force required to keep the nose at a normal ascent angle; and the stab trim was not responding to my inputs. However; there were no cautions or aurals. I stopped accelerating at 200 KIAS; but kept a normal climb rate going to achieve higher altitude to work on the problem. Climbing past approximately 10000 ft; I wanted to check to see if either of the disconnect switches was the cause of the inactive stab trim. I disconnected the stab trim using the left stab disconnect switch and had the FO run the stab trim caution QRH to follow a logical sequence of events to reset it and possibly help with the problem. We ended up resetting stab/mach trim; and we were back to where we were before I disconnected. At one point in the remaining climb I requested autopilot engagement; but turned it off again shortly thereafter because I was not comfortable with the amount of potential back force that would occur if the autopilot disconnected automatically. I did hold for the approximately 3 seconds that it was engaged. We were now level at 18000 ft where we had requested to remain in order to begin the communications portion of our problem solving (Maintenance; Dispatch; Flight Attendant; passengers; etc). It was then that I noticed the trim was above 9; but it was static. I don't know when or how in the sequence of events it got there; but I had not noticed any additional control forces beyond what I had been inputting. Furthermore; there had been no aural and no caution of any kind. After a few seconds; the numerical trim meter went nose up by .2 (one standard increment) and stopped there. Shortly after; we saw that it went up another .2; and that's when I first noticed a further increase in required force and immediately called for the stab trim runaway immediate action items and the QRH checklist. By the time we disconnected; the trim had reached 10 nose up and remained there for the rest of the flight (the indicator went blank when the circuit breakers were pulled; but the mechanic who met us in ZZZ2 said that it was still at 10 when we were parked at the gate). We had declared an emergency with center who told us that ZZZ3 was about 5 miles away. I was not comfortable spiraling down from 18000 ft with that controllability issue; so we were offered and accepted ZZZZ; approximately 40 miles to our northeast. We descended and then slowed per the QRH; which helped the controllability; especially after flaps were extended to 8 degrees to set up for a flaps 20 landing. The First Officer advised the Flight Attendants and the passengers as we were setting up for the visual approach at ZZZ2. ATC put us on a 10 mile final and had emergency equipment waiting for us. The landing was uneventful besides a higher-than-normal approach and landing speed; and we taxied off the runway and to the gate followed by the emergency vehicles.Callback conversation with reporter revealed the following info: The reporter stated that his air carrier's maintenance personnel determined that a trim switch caused the system to fail; but that report is questionable because the trim did not operate from either pilot's yoke control switch. The normal trim setting for a heavily loaded aircraft is about 8 units of nose up trim. This aircraft's trim failed after the takeoff trim was set and then ultimately drifted to about 10 units requiring a force estimated to be about 50 pounds to keep it in level flight. The force would have been considerably higher had the aircraft been accelerated above a slow maneuvering speed.

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.