Regional Jet 700 ER/LR (CRJ700)
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
Upon receiving approach clearance for the ZZZZZ XX Approach; [the] FO (First Officer) disengaged autopilot and began [a] gradual descent on approach while configuring to Flaps 20 and slowing to 170 kt. As I read back approach clearance to ATC; we crossed ZZZZZ1 and I heard the trim clacker activate. I thought that this was [the] FO adjusting to nose down trim as we were descending and configuring. After a few seconds; I asked if he was commanding the abnormally long trim down and he replied that he wasn't. The trim then stopped and appeared to remain stable. It then started a nose-up motion uncommanded. I verified that [the] FO did not inadvertently have his finger on the trim switch; and I [was] certain that mine was not. I then realized that this appeared to be a stab trim malfunction and went through and verbalized the immediate action items.Upon successfully disconnecting the stab and Mach trim; I asked [the] FO if he needed assistance in adding extra pressure on the controls and he informed me that they felt fine; just marginally heavier than normal. I elected to continue the approach as the uncommanded action was no longer occurring and I determined that an approach to landing would have been the safer; more stable option over quickly changing configuration and executing a go-around in a nose-down trim. We continued and landed without further incident. I sent Dispatch a text informing them of the event; and contacted Maintenance Control following entering a discrepancy in the aircraft maintenance logbook.
CRJ-700 Captain reported a trim malfunction on descent and followed QRH procedures to land successfully.