Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human-Machine Interface; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew FLC Overrode Automation; Flight Crew Returned To Clearance
Aircraft; Human Factors
On climb out; we were flying the departure; climbing through FL180; and had been cleared direct to the JEWLS way point. We were subsequently directed to maintain present heading for traffic. The PF (Pilot Flying) selected HDG (Heading) mode with the autopilot on. The HDG annunciation moved into the active position and turned green. However; at the JEWLS way point; the aircraft turned on course as though it was still in FMS (Flight Management System) mode. ATC queried us about whether we were still on our assigned heading or had turned at JEWLS. This is what prompted us to notice the discrepancy. We responded that we had turned on course and the Controller had no further instructions for us. After this; we investigated and found the autopilot to still be indicating HDG mode; but operating as though in FMS mode. PF had synced the heading; by habit; after the turn. We subsequently obtained a clearance direct to HYS VOR; which was on our flight plan and proceeded with the flight with no further incidents. Of note: the FMS flashed the message: 'FMS-FMS DISAGREE' momentarily immediately after this event and the two AHRS (Attitude Heading Reference System) headings differed by 2 degrees throughout the flight. I suspect that the primary cause of this event is a malfunction with the automation. The secondary cause was lack of pilot awareness of whether the aircraft was functioning as expected/commanded. Pilots pay special attention to flight modes during off-schedule clearances such as this assigned heading.
CRJ-200 First Officer reported autopilot malfunction and lack of situational awareness caused a heading deviation.