Regional Jet 200 ER/LR (CRJ200)
Flight Crew Air Transport Pilot (ATP)
Confusion; Distraction; Workload
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action; General Maintenance Action
ATC Equipment / Nav Facility / Buildings; Aircraft
We were being vectored to join the final for an ILS PRM 9R. We had been cleared for the approach and I had armed approach mode on the FCP. We had just captured the localizer and I noticed the aircraft had started an uncommanded climb; reaching approximately 7;100 feet and the Flight Director had become intermittent; flashing OFF and ON on both sides. I disconnected the autopilot and returned to our assigned altitude of 7;000 feet. I called for the First Officer to remove the Flight Director and flew the remainder of the approach raw data for a normal approach and landing. The Flight Director or possibly the glide slope had become intermittent and caused the aircraft to climb approximately 100 feet from our assigned altitude. I decided rather than try to re-engage the autopilot; the best course of action would be to hand fly the approach. After arriving; we contacted Maintenance and wrote up the Flight Director.
A CRJ-200 climbed about 100 feet uncommanded as the autopilot was capturing the localizer on an ILS PRM so the Captain disconnected the autopilot and hand flew the approach.