Narrative:

Upon leveling at FL240; we experienced a complete failure of ahrs [altitude and heading reference system] system number 1; followed by multiple pfd & mfd screen failures on the captain's flight instruments; along with an associated FD flag; and yd 1 inoperative status message. I was the pilot flying at the time; and assumed manual control of the aircraft. Without any attitude or heading reference on my pfd I transferred the flight controls to the first officer who still had working ahrs on his side; he would remain as pilot flying for the duration of the flight. We determined this as a time threat and created a plan of action. The airplane had just been on a mechanical delay; where they replaced the number 1 ahrs unit; so we knew it had some history on it. We decided to run the QRH for 'attitude and heading reference system failure'. After completion of the checklist; we were still unable to reengage the aircraft's autopilot; but were able to display ahrs #2 data on the captain pfd. ATC was notified of the system failure. Dispatch was contacted; and after talking to the controller advised that they would like us to [return to departure airport] as opposed to continuing. The flight had been planned with round trip fuel so we had enough gas to make it back; and have a fallback alternate; and still over 1000 pounds of extra fuel. We coordinated with ATC for a return. Both the flight attendant and the passengers were briefed as well on the situation and the decision to return. Upon initial flap extension; we received a stabilizer trim & mach trim caution message. The QRH was run for the stabilizer trim caution message; and initially resolved. Upon further extension of the flaps to 45; the stabilizer trim caution message reappeared; the QRH was run again for the reappearance of the stabilizer trim caution message; and directed us to use stabilizer trim CH2 for landing. We landed uneventfully; and the aircraft was written up and pulled out of service for maintenance. Mechanical failure of ahrs unit. Despite having replaced the ahrs unit; it obviously did not solve the original maintenance issue; as we had it fail completely on us in flight. Not sure how to prevent this from recurring...it was a faulty ahrs computer/system.

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Original NASA ASRS Text

Title: CRJ-200 flight crew reported returning to departure airport after experiencing loss of the Captain's AHRS system.

Narrative: Upon leveling at FL240; we experienced a complete failure of AHRS [Altitude and Heading Reference System] system number 1; followed by multiple PFD & MFD screen failures on the Captain's flight instruments; along with an associated FD flag; and YD 1 INOP status message. I was the pilot flying at the time; and assumed manual control of the aircraft. Without any attitude or heading reference on my PFD I transferred the flight controls to the First Officer who still had working AHRS on his side; he would remain as Pilot Flying for the duration of the flight. We determined this as a time threat and created a plan of action. The airplane had just been on a mechanical delay; where they replaced the number 1 AHRS unit; so we knew it had some history on it. We decided to run the QRH for 'Attitude And Heading Reference System Failure'. After completion of the checklist; we were still unable to reengage the aircraft's autopilot; but were able to display AHRS #2 data on the Captain PFD. ATC was notified of the system failure. Dispatch was contacted; and after talking to the controller advised that they would like us to [return to departure airport] as opposed to continuing. The flight had been planned with round trip fuel so we had enough gas to make it back; and have a fallback alternate; and still over 1000 pounds of extra fuel. We coordinated with ATC for a return. Both the Flight Attendant and the passengers were briefed as well on the situation and the decision to return. Upon initial flap extension; we received a STAB TRIM & MACH TRIM caution message. The QRH was run for the STAB TRIM Caution message; and initially resolved. Upon further extension of the flaps to 45; the STAB TRIM Caution message reappeared; the QRH was run again for the reappearance of the STAB TRIM Caution message; and directed us to use STAB TRIM CH2 for landing. We landed uneventfully; and the aircraft was written up and pulled out of service for maintenance. Mechanical Failure of AHRS unit. Despite having replaced the AHRS unit; it obviously did not solve the original maintenance issue; as we had it fail completely on us in flight. Not sure how to prevent this from recurring...It was a faulty AHRS computer/system.

Data retrieved from NASA's ASRS site 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.