Flight Crew Air Transport Pilot (ATP)
Confusion
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Aircraft Equipment Problem Dissipated
Aircraft
During vectors to ILS Approach aircraft HSI/Compass failed. First Officer was flying pilot at time of event and the auto pilot was engaged. The weather was in and out of towering cumulus clouds; cloud bases at approximately 2;500 FT and visibility was 10 plus mile. We were in a descending left turn to heading 320 degrees and altitude 5;000 FT MSL. As aircraft started to level and fly heading 320 degree both First Officer's and Captain's HSI began spinning causing aircraft to enter approximately 25 degree right bank turn. 'EFIS COMP MON' amber CAS illuminated with associated master caution during event. The autopilot continued to follow the HSI till I (Captain) disengaged and leveled wings using attitude indicator along with outside visual references. I (Captain) took over pilot flying duties for remainder of flight. After turning autopilot off; our heading varied from assigned by approximately 30 degrees and altitude was 200 FT low. While avionics failure was occurring Approach tried calling several times to assign lower altitude and intercept heading vector; but we were unable to initially respond. When we cleared clouds on the north side of final approach course we had a clear view of runway. We advised Approach that we had avionics failure and needed a visual to airport. Approach cleared us for the visual approach approximately 15 miles from runway. Soon after; leveling wings; on final approach course HSI headings returned to normal and all cautions disappeared.
CRJ700 Captain experiences dual HSI failure during approach with the autopilot attempting to follow the spinning HSI's. The Captain assumes control and levels the wings and once in VMC a visual approach is requested. Once established the HSI headings return to normal.