Narrative:

On the tralr departure at 7;000 ft MSL as we accelerated the auto pilot trimmed full (or approximately so) nose down. The system disengaged the auto pilot (as it is designed to do with a trim malfunction or out of trim situation) simultaneously as the pilot flying was reducing the power and the supporting pilot was receiving and responding to the radio call to climb to 8;000 ft. The pilot flying immediately recognized the out of trim situation; applied back pressure and communicated to the supporting pilot what was happening. Due to the excessive down force on the control column; the aircraft was loosing altitude (at that point about 200 ft.) the supporting pilot without hesitation pressed the secondary pitch trim button and trimmed nose up. The control forces were reduced significantly and the climb to 8;000 ft was resumed. The non-flying pilot communicated to departure control that we were experiencing difficulty with the trim system. We were issued a heading and altitude and asked if we required assistance or wished to declare an emergency. After a short assessment the auto pilot was successfully reengaged and we stated we would be continuing on and had corrected the problem. As time permitted we reviewed the checklist for the intermittent caution lights we had observed. At this point we thought we had an intermittent problem that had apparently gone away. This has been our experience with the sovereign on several systems in the 10 months we have been flying it; so it seemed reasonable to assume. Later in the flight the primary pitch system failed. After running the appropriate checklist items and communicating with cessna support over the sat phone; it was obvious we had no option but to leave rvsm airspace and coordinate a diversion to where maintenance was available. We maintained a consistent and lower indicated airspeed than normal to reduce/eliminate any need for trimming until configuration for landing. The secondary trim system worked well; making the aircraft easy to fly; we just could not engage the autopilot without the primary trim system. The pilot flying flew a textbook approach and landing. We did not declare an emergency; but agreed we would immediately if there was any indication of secondary trim malfunctions; or other complicating issues. Lessons learned were very positive. We did a lot of 'right' things; including clearly communicating the problem between pilots; keeping ATC informed (which resulted in them simplifying our clearance;) and using our on board resources and cessna over the sat phone. We also thought ahead and discussed/briefed 'what if' the secondary trim failed; how the approach would differ from normal; and how to accomplish a go around with the secondary trim that moves the horizontal stabilizer at a much slower rate. The airplane entered the cessna service center that evening and required a new pitch trim actuator.

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Original NASA ASRS Text

Title: CE680 Captain describes a runaway stabilizer trim situation during departure resulting in autopilot disengagement and a small altitude deviation. The secondary trim system is used to the stabilizer and eventually the autopilot is engaged. Enroute the problem reoccurs and the crew elects to divert to a maintenance station.

Narrative: On the TRALR departure at 7;000 FT MSL as we accelerated the auto pilot trimmed full (or approximately so) nose down. The system disengaged the auto pilot (as it is designed to do with a trim malfunction or out of trim situation) simultaneously as the pilot flying was reducing the power and the supporting pilot was receiving and responding to the radio call to climb to 8;000 FT. The pilot flying immediately recognized the out of trim situation; applied back pressure and communicated to the supporting pilot what was happening. Due to the excessive down force on the control column; the aircraft was loosing altitude (at that point about 200 FT.) The supporting pilot without hesitation pressed the secondary pitch trim button and trimmed nose up. The control forces were reduced significantly and the climb to 8;000 FT was resumed. The non-flying pilot communicated to Departure Control that we were experiencing difficulty with the trim system. We were issued a heading and altitude and asked if we required assistance or wished to declare an emergency. After a short assessment the auto pilot was successfully reengaged and we stated we would be continuing on and had corrected the problem. As time permitted we reviewed the checklist for the intermittent caution lights we had observed. At this point we thought we had an intermittent problem that had apparently gone away. This has been our experience with the Sovereign on several systems in the 10 months we have been flying it; so it seemed reasonable to assume. Later in the flight the primary pitch system failed. After running the appropriate checklist items and communicating with Cessna support over the SAT phone; it was obvious we had no option but to leave RVSM airspace and coordinate a diversion to where maintenance was available. We maintained a consistent and lower indicated airspeed than normal to reduce/eliminate any need for trimming until configuration for landing. The secondary trim system worked well; making the aircraft easy to fly; we just could not engage the autopilot without the primary trim system. The pilot flying flew a textbook approach and landing. We did not declare an emergency; but agreed we would immediately if there was any indication of secondary trim malfunctions; or other complicating issues. Lessons learned were very positive. We did a lot of 'right' things; including clearly communicating the problem between pilots; keeping ATC informed (which resulted in them simplifying our clearance;) and using our on board resources and Cessna over the SAT phone. We also thought ahead and discussed/briefed 'what if' the secondary trim failed; how the approach would differ from normal; and how to accomplish a go around with the secondary trim that moves the horizontal stabilizer at a much slower rate. The airplane entered the Cessna Service Center that evening and required a new pitch trim actuator.

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.