Narrative:

Our aircraft was equipped with ahrs and per company policy we are required to take off in dg mode; with no flags; heading slewed to the known magnetic heading on runways with known magnetic anomalies. Runway 13 at lga is one such runway and we followed this procedure prior to taking the active runway. During climbout I believe we had at least one EFIS comp mon master caution while on an assigned heading. Shortly thereafter; and still on climbout; we were assigned direct to a fix. The heading flags and EFIS comp mon messages had disappeared. When we selected navigation mode we were still climbing and the aircraft appeared to be going to the fix. When the aircraft continued to turn past the fix I asked ATC for a heading instead and we used our standby compass for guidance. We briefly leveled off and; with no flags present; I compared our pfd compass headings to the standby compass and switched us back to magnetic mode one at a time. When I reached over to switch first officer (first officer) switch to back to magnetic mode it was already in that position. I asked ATC to reclear us to the fix. When we went back to navigation mode the course depiction started turning quickly which; to me; indicated an equipment malfunction. I then instructed my first officer to go back to heading mode. We were also back in the climb and I asked for another heading to the fix. I also mentioned to the controller that I would not be able to work on the issue until we were straight and level. He handed me off to the next controller; who was aware of the issue but queried for further details and I told him we were having a problem with our gyros and asked him to remain on a heading on the course. Once we were leveled off again; I consulted the QRH even though we had no flags or master caution at the time. At this time; our standby compass and pfd headings were all indicating the same course. I asked the controller to give us a heading to the next fix and when navigation mode was selected the navigation system was on course and we had no further issues. I should have asked the first controller for a level off but he seemed stressed and anxious to get us out of his airspace so I asked him for a heading instead; thinking that would temporarily solve the problem even though I know that a standby compass is not correct until we are in straight; level; unaccelerated flight. I am used to this procedure but the ahrs system has often caused complications in cruise flight when departing from runways with known magnetic anomalies; regular EFIS comp mon caution messages; further distraction for the crew during high workload periods; aborted takeoffs. It would be extremely helpful to have these systems replaced with IRS equipped aircraft.

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Original NASA ASRS Text

Title: CRJ-900 flight crew reported a heading problem with the AHRS system on climb out after a night departure.

Narrative: Our aircraft was equipped with AHRS and per company policy we are required to take off in DG mode; with no flags; heading slewed to the known magnetic heading on runways with known magnetic anomalies. Runway 13 at LGA is one such runway and we followed this procedure prior to taking the active runway. During climbout I believe we had at least one EFIS COMP MON master caution while on an assigned heading. Shortly thereafter; and still on climbout; we were assigned direct to a fix. The heading flags and EFIS COMP MON messages had disappeared. When we selected NAV mode we were still climbing and the aircraft appeared to be going to the fix. When the aircraft continued to turn past the fix I asked ATC for a heading instead and we used our standby compass for guidance. We briefly leveled off and; with no flags present; I compared our PFD compass headings to the standby compass and switched us back to MAG mode one at a time. When I reached over to switch First Officer (FO) switch to back to MAG mode it was already in that position. I asked ATC to reclear us to the fix. When we went back to NAV mode the course depiction started turning quickly which; to me; indicated an equipment malfunction. I then instructed my FO to go back to heading mode. We were also back in the climb and I asked for another heading to the fix. I also mentioned to the controller that I would not be able to work on the issue until we were straight and level. He handed me off to the next controller; who was aware of the issue but queried for further details and I told him we were having a problem with our gyros and asked him to remain on a heading on the course. Once we were leveled off again; I consulted the QRH even though we had no flags or master caution at the time. At this time; our standby compass and PFD headings were all indicating the same course. I asked the controller to give us a heading to the next fix and when NAV mode was selected the navigation system was on course and we had no further issues. I should have asked the first controller for a level off but he seemed stressed and anxious to get us out of his airspace so I asked him for a heading instead; thinking that would temporarily solve the problem even though I know that a standby compass is not correct until we are in straight; level; unaccelerated flight. I am used to this procedure but the AHRS system has often caused complications in cruise flight when departing from runways with known magnetic anomalies; regular EFIS COMP MON caution messages; further distraction for the crew during high workload periods; aborted takeoffs. It would be extremely helpful to have these systems replaced with IRS equipped aircraft.

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.