Crj-200 captain reported an altitude deviation when he lost ahrs data in cruise at FL330.

Attributes
ACN	1063256
Time
Date	201301
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Aircraft 1
Make Model Name	Regional Jet CL65 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	AHRS/ND
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance

Narrative:

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.

Original NASA ASRS Text

Title: CRJ-200 Captain reported an altitude deviation when he lost AHRS data in cruise at FL330.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2013 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.