A CRJ200's EICAS alerted AP PITCH TRIM and after the QRH procedure the STAB CH 1 caution alerted. Both cautions plus a MACH TRIM alert had been entered in the maintenance log nine times in the previous eight days and written off.

Narrative

During cruise flight at an intermediate descent altitude the EICAS posted an 'AP PITCH TRIM' caution message. We actioned the QRH which requires the autopilot to be disconnected; stabilizer re-trimmed and autopilot reengaged. While actuating the trim manually; 'STAB CH 1' status message posted and was subsequently manually reengaged. 'STAB CH 1' status message posted twice more on descent and the third time we decided not to reengage and land with one stab trim channel operating. We wrote up the discrepancy upon landing but during further examination of the logbook; we noticed nine previous write-ups in the preceding eight days regarding the stabilizer trim including: AP PITCH TRIM message; STAB CH 1 message; and MACH TRIM message. There was also further evidence of similar discrepancies going back further but the previous AFD log was not in the aircraft. All write-ups were signed off with: 'ops check good'; 'fault no longer exists'; 'could not duplicate'; 'reset system in accordance with...' etc. Repairs were made in most instances; however in a single day there were four separate write-ups on the stabilizer system with only one being disposed of with an equipment repair. I don't know the exact policies of the Maintenance Department; but on a system so critical to safe operation of the aircraft; I believe a thorough investigation of the malfunctions should have been undertaken much sooner.