Date: 202002
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: Marginal
Light: Daylight
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Navigational Equipment and Processing
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

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.


Second narrative: In cruise flight the Captain's AHRS system went out and his FPD and MFD displays went blank and came back several times. The Captain also got a FD flag and we got a YD 1 inop status message. Captain did [a] great job working the problem and had me fly the airplane while he communicated with company; ATC; FA (Flight Attendant) and pax (passengers). We decided to return in coordination with the company. On approach we also received stab trim and mach trim caution messages and ran the QRH and followed its guidance and landed without issue.


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