Narrative:

I was the pilot flying. The first officer was pilot monitoring. A company check airman was riding on the jumpseat administering a line-check. We were climbing out of ZZZ on an assigned 100 degree heading; leveling at 5;000 ft when the autopilot disengaged. As I took control of the aircraft my eadi showed aircraft pitched slightly down and in 5 degree bank to the right. A quick scan of the instruments showed the vsi in a 400 ft climb and the standby attitude indicator confirmed the climb and that the wings were level; during this time the first officer also alerted me to the climb. It was then that I realized that my eadi had quit and made corrections to return the aircraft to 5;000 ft on the 100 degree heading using the standby attitude indicator and the evsi. During the transition of recovering the aircraft to the assigned altitude and heading our altitude reached approximately 5;200 ft. At that point ID802 panel showed a roll mismatch; and my heading indicator had precessed 20 degrees; further confirming my assumption of the failed instruments. Realizing that my flight instruments had failed I transferred the controls to the first officer and then went to the abnormal checklist to see if our problem was addressed. Unable to find any checklist that I felt would address our current symptoms; I elected to return to the field and have maintenance look at the aircraft. I then notified ATC of our intention to return to the field and that we would not need any further assistance. ATC then assigned a visual approach to runway 23. I then notified the flight attendant that we had a flight instrument malfunction and that we would be returning to the field. I also stated that it would be a normal landing and asked her to tell the passengers. I would speak to them on the ground. I also called ZZZ operations and let them know that we would be returning with a flight instrument malfunction and we would need a gate. We then ran all required checklists before landing and landed without further incident. Once on the ground I briefed the passengers of our situation and told them that maintenance was on the way to rectify the problem. Ahrs failed in flight.

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Original NASA ASRS Text

Title: A DHC-8-300 Captain's AHRS failed after takeoff causing the autopilot to disconnect and continue climbing. As the heading drifted; the Captain gave the aircraft to the First Officer and the aircraft was returned to the departure airport. An emergency was not declared.

Narrative: I was the Pilot Flying. The First Officer was Pilot Monitoring. A company Check Airman was riding on the jumpseat administering a line-check. We were climbing out of ZZZ on an assigned 100 degree heading; leveling at 5;000 FT when the autopilot disengaged. As I took control of the aircraft my EADI showed aircraft pitched slightly down and in 5 degree bank to the right. A quick scan of the instruments showed the VSI in a 400 FT climb and the standby attitude indicator confirmed the climb and that the wings were level; during this time the First Officer also alerted me to the climb. It was then that I realized that my EADI had quit and made corrections to return the aircraft to 5;000 FT on the 100 degree heading using the standby attitude indicator and the EVSI. During the transition of recovering the aircraft to the assigned altitude and heading our altitude reached approximately 5;200 FT. At that point ID802 panel showed a roll mismatch; and my heading indicator had precessed 20 degrees; further confirming my assumption of the failed instruments. Realizing that my flight instruments had failed I transferred the controls to the First Officer and then went to the abnormal checklist to see if our problem was addressed. Unable to find any checklist that I felt would address our current symptoms; I elected to return to the field and have Maintenance look at the aircraft. I then notified ATC of our intention to return to the field and that we would not need any further assistance. ATC then assigned a visual approach to Runway 23. I then notified the Flight Attendant that we had a flight instrument malfunction and that we would be returning to the field. I also stated that it would be a normal landing and asked her to tell the passengers. I would speak to them on the ground. I also called ZZZ Operations and let them know that we would be returning with a flight instrument malfunction and we would need a gate. We then ran all required checklists before landing and landed without further incident. Once on the ground I briefed the passengers of our situation and told them that Maintenance was on the way to rectify the problem. AHRS failed in flight.

Data retrieved from NASA's ASRS site as of April 2012 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.