Date: 201712
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Dusk
Aircraft: Regional Jet 700 ER/LR (CRJ700)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Autoflight Yaw Damper
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Human factors: Time Pressure; Troubleshooting
Anomaly: Aircraft Equipment Problem Less Severe
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: We were operating from ZZZ-ZZZ1. Due to delays into ZZZ1 we pushed back out of the gate at XB:24 local from the original time of XA:07. We had light to moderate snow in ZZZ so after pushback we proceeded to the deice pad to get the aircraft free of contaminants before takeoff. We departed ZZZ at XB:59. The flight started mostly in IMC conditions but by the time we began our descent on the arrival we were in VMC. We were at 10;000 ft and approach was beginning to vector us for the LOC due to strong winds in ZZZ1. There were strong winds in ZZZ1 that evening but it was VMC with visibility of 10 SM. The CA was PF and I was PM. At 10;000 ft while heading to ZZZ1; we had the autopilot on and it was coupled to the CA's side. Suddenly the autopilot disconnected. We had no indications other than a Yaw Damper 1 status message. We reengaged the autopilot; Yaw damper 1; and continued with our descent to 6;000 ft. At approximately 6;000 ft; the captain's altitude indicator started showing an increasing roll to the left; the autopilot disconnected again; we got and EFIS COMP MON caution message and the captain's attitude indicator continued its roll to the left until it was completely inverted. Due to the increasing bank angle on the attitude indicator; the captain's screen decluttered and we had an almost continuous 'BANK ANGLE' aural warning. While this was happening; my attitude indicator indicated a slight roll to the right and showed an amber ROLL and PIT flag on the lower portion of the attitude indicator. The captain's airspeed indications also did not match what was on the standby instruments nor did it match my instruments. At this point; the captain had taken manual control after the autopilot disengaged and we both tried to figure out the problem while using the outside horizon to determine our attitude since it was VMC and confirming it with our standby attitude indicator. ATC had cleared us to 4;000 ft and right heading 060. On request from the CA; I reported to the controller that we had an instrumentation error. The controller asked if we needed any assistance and we decided to [advise ATC] since we weren't able to trust our speed; altitude; and attitude indications. The controller asked us if we still wanted to go to ZZZ1. Since we were very close to the airport; and in VMC conditions; the CA agreed to proceed to ZZZ1. I replied to the controller; 'Affirmative' to confirm our intentions to land at ZZZ1. Meanwhile; the CA was flying using visual references. Keeping the aircraft level with the horizon. The captain and I continued scanning our instruments and noticed that my attitude indicator started to come back to wings level and that my airspeed; altitude; and attitude all matched the standby instruments. The captain decided that since my side matched the standby that I should take the controls and I did. I continued to fly manually while the captain talked on the radio and assisted me by bugging speeds and altitude. ATC stated that they planned to put us on a right downwind for the visual since the meteorological conditions permitted it. Once aligned with the extended centerline; we had the runway in sight and got cleared for a visual. At this point; my instruments looked accurate but I was still double checking with the standby instruments and the captain kept double checking my airspeed and altitude to make sure we were stabilized on glide path. Aside from the malfunctioning instruments; we were flying the approach as normal. We landed the aircraft safely and proceeded to the gate as normal. This incident happened very close to the ground; flying during evening hours; in congested airspace. This made the situation a bit more challenging. We were ready for the approach. We had loaded it into the FMS and had briefed it way before we initiated our final descend into ZZZ1. However; when faced with the instrumentation failure that we experience; I felt we did not have as much time as we would have liked to try to troubleshoot the problem. We were very close to landing and decided that since the meteorological conditions were favorable; we should just go ahead and land the aircraft. As a crew we would have liked more time to run our QRH procedures; as trained by the company; but at the time this did not seem suitable since we more than likely would have had to be vectored out somewhere away from all the traffic. With night time approaching; as well as weather from the west; we decided that time was critical and landing immediately was the better decision. The aircraft was never in an undesired state. We are both very familiar with this airspace and having the airport in sight when this happened helped us maintain our situational awareness up and maneuver the aircraft to a safe landing. I believe that as a cockpit crew; the CA and I had great communication and good CRM. However; due to the time constraints; we were unable to brief the cabin crew like we wanted. Everything happened very quickly and we never thought it was going to end up badly so we never briefed them. In hindsight; we should have briefly told them what was happening and that we were landing immediately just in case something did happen upon touchdown and they could proceed in the way they were trained. Also; from a human factors point of view; I believe the CRJ does a poor job in telling the pilot that the AHRS system has failed. We are used to receiving caution and warning messages on our EICAS but for this particular system failure all we got was a EFIS COMP MON message. I remember this from ground school but unfortunately; during day to day line flying; when we see an EFIS COMP MON message we normally just associate it with magnetic interference so we are a bit desensitized to it. When we got this message during this incident; we knew it was the AHRS acting up but it takes a lot of crosschecking between instruments to figure out which one is right and which is wrong. I believe that a more efficient system should be develop to let the pilot know exactly what's being affected so the pilot has to work less determining the problem and use his time to troubleshoot. If I ever encounter an event like this again; I think trying to slow things down might help. I will use this as a learning experience and take away the things that worked and leave the ones that didn't so that I can be more prepared to deal with this in the future.




Synopsis: CRJ-700 First Officer reported several messages and instrument indications associated with a malfunction of the Attitude and Heading Reference System.