Narrative:

During initial descent; the captain/pilot-flying; noticed a pitch trim annunciation on his primary flight display (pfd). He took a firm grip of the control wheel and disconnected the autopilot. The aircraft made a 2-3 abrupt pitch-up movement. He tried to use electric trim and found it inoperative. He then tried manual trim and found it to be frozen. He verbalized this to me at this point and then tried pushing harder on the trim wheel at which time it 'broke free' and operated normally. He continued to handfly the aircraft a while longer; then; satisfied that the trim seemed to operate normally; he re-engaged the autopilot and we conducted the rest of the flight under normal operations; with no other abnormal pitch trim indications. During pre-flight; the pitch trim tested and felt normal through its full range of operation. I am not sure what other tests could have been performed on the trim system prior to departure. Perhaps we should have a new policy of periodically hand-flying the aircraft during climb or cruise to ensure that there are no abnormal trim issues or frozen trim. My understanding from feedback through the maintenance department and the chief pilot's office; this problem is caused from moisture in the trim system. Perhaps the packing grease on this part of the system needs to be included on future regular inspections.

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Original NASA ASRS Text

Title: During initial descent in a CE-560XLS Citation aircraft; Captain noticed a Pitch Trim annunciation on his Primary Flight Display (PFD). Aircraft made an abrupt pitch up movement after he disconnected the autopilot. Electric Trim was inoperative and Manual Trim frozen. After pushing harder on Trim wheel; Manual Trim 'broke free' and operated normally.

Narrative: During initial descent; the Captain/Pilot-Flying; noticed a Pitch Trim annunciation on his Primary Flight Display (PFD). He took a firm grip of the control wheel and disconnected the Autopilot. The aircraft made a 2-3 abrupt pitch-up movement. He tried to use Electric Trim and found it inoperative. He then tried Manual Trim and found it to be frozen. He verbalized this to me at this point and then tried pushing harder on the Trim wheel at which time it 'broke free' and operated normally. He continued to handfly the aircraft a while longer; then; satisfied that the trim seemed to operate normally; he re-engaged the autopilot and we conducted the rest of the flight under normal operations; with no other abnormal pitch trim indications. During pre-flight; the Pitch Trim tested and felt normal through its full range of operation. I am not sure what other tests could have been performed on the Trim System prior to departure. Perhaps we should have a new policy of periodically hand-flying the aircraft during climb or cruise to ensure that there are no abnormal trim issues or frozen trim. My understanding from feedback through the Maintenance department and the Chief Pilot's office; this problem is caused from moisture in the Trim System. Perhaps the packing grease on this part of the system needs to be included on future regular inspections.

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.