Regional Jet 200 ER/LR (CRJ200)
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation - Speed All Types; Deviation - Track / Heading All Types
Aircraft Equipment Problem Dissipated; Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem; Flight Crew FLC complied w / Automation / Advisory; General Maintenance Action
Manuals; Chart Or Publication; Aircraft
We were 1;000 FT above level off for the 12;000 FT restriction on the arrival. OFF flags appeared in the Captain's ADI and HSI; accompanied by a Master Caution; autopilot disconnect and EFIS COMP messages. I immediately assumed manual control referencing PFD 2. I leveled off at 12;000 FT and cross checked the standby instruments and outside references. They seemed okay initially. The First Officer noticed that there was an YD1 INOP message and reset that. There were also roll and heading comparator flags in PFD2. I maintained wings level briefly to see if the AHRS1 would in flight align. The First Officer noted a 30 degree anomaly between both heading systems and the standby compass. I confirmed this; took the radios and called for the EFIS COMP MON checklist. After what seemed like more than a minute AHRS1 in flight aligned. There was still an EFIS COMP message with roll and heading comparator flags in both PFD's. The frequency was congested and the situation dynamic so I did not call ATC right away. I noticed that we were slightly right of course and made a shallow left turn to intercept course. I continued to fly cross cockpit and noticed that ADI2 showed level flight while the aircraft was in nearly 10 degrees of right bank. This was confirmed with a careful cross check of the standby ADI and outside references. It seemed unbelievable to me but in fact it was true. Because of this discrepancy; I elected to not call for the QRH procedure for AHRS1 failure. This would only send this incorrect roll information to ADI1. Approach queried us about our speed. At this point I remembered that the last controller had assigned 300 KTS. I reported our actual speed of 250 KTS and added power. I also advised Approach that our primary attitude and heading instruments had failed and that we were on the standby systems. I requested radar vectors. ATC issued an altitude change to the jet coming up behind us. He promptly complied. ATC assigned several incremental heading changes to put us on downwind. Once we were wings level on downwind we accurately adjusted both heading systems to the standby compass. After a minute of wings level flight on downwind both AI's also crosschecked wings level with the standby ADI and outside references. I switched to FD2 and engaged the autopilot. We monitored the systems closely. The remainder of the flight was uneventful. Maintenance found no discrepancy but the subsequent flight experienced a loss of PFD1 at 300 FT on final approach. That one cleared at touchdown and resulted in replacement of AHRS1. The autopilot and pilot flying's instruments shutting off just before level off with several messages to sort through. A marked difference between the remaining instruments; I think we all did our best under the circumstances. In 30 years as a pilot this is the first 'dual ADI failure' I have had; if you can call it that. I am not sure why AD2 was off slightly but the equipment proved its ability to in flight align. The only thing I would bring up is that the QRH is incomplete. It does not include the in flight alignment procedure described in the PRM. Good luck making that happen. In the mean time I hope the detailed info in this report of a successful in flight alignment will be shared with my fellow RJ pilots.
A CRJ200 Captain reported a dual AHRS failure during descent including the EFIS COMP message; ADI and HSI OFF flags. The EFIS COMP MON Checklist was completed and the system reset before landing; but failed on the next flight and AHRS 1 was replaced.