Regional Jet CL65; Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Flight Crew FLC Overrode Automation; Flight Crew Returned To Clearance
Aircraft
While at FL330; we lost AHRS data to to the #1 PFD. We transferred the flight director and autopilot to the First Officer's side who had been the pilot not flying. After a few minutes the #1 PFD data reinitialized itself. We returned the flight director and autopilot to the Captain's side. The aircraft began descending. I immediately disconnected the autopilot; assumed manual control and returned to FL330. ATC queried our altitude as we were returning to FL330; we reported the malfunction and requested a lower altitude. Upon arrival; the discrepancy was entered into the maintenance log; and Maintenance was called.
CRJ-200 Captain reported an altitude deviation when he lost AHRS data in cruise at FL330.