Commercial Fixed Wing
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 52
Workload; Human-Machine Interface; Training / Qualification
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Human Factors
I was acting as pilot flying on the flight to ZZZ. While flying on our assigned course direct to the ZZZ airport; approximately 100 miles from our destination; while conducting the arrival and approach briefings; ATC Center assigned us to turn left 10 degrees; which I complied with by selecting heading mode on the FCP; and selecting the desired heading with the heading bug. Several minutes later; the Controller; again; assigned us to proceed direct to the ZZZ airport. I selected in the FMS direct to the ZZZ airport; confirmed the selection with my captain; and executed the flight plan modification. However; I had neglected to select NAV mode; which resulted in the aircraft continuing on its previously assigned heading for several minutes while I finished the arrival briefing; resulting in the course to show a full-scale deflection to the left (south). Upon finishing the briefing; I realized the missed step; and immediately turned back toward the course and armed NAV mode. Having recently switched over to ZZZ approach; within several minutes the controlled queried us about our position; informing us we were left of course. We notified the controller that we were rejoining the course. The controller then assigned us to proceed direct to the ZZZ airport again; which we selected in the FMS; confirmed; and executed; this time ensuring NAV mode was engaged. The flight continued without issue.This event was caused by lack of recent flight experience; as well as momentary task-saturation.This has not been a reoccurring trend for me during training or during revenue operations. I plan to continue to maintain a high level of situational awareness in the cockpit to trap threats before they become errors. I also plan to ensure I am making appropriate FCP selections when I am making an adjustment to our course.
Air Carrier First Officer reported a heading deviation and cited lack of recent flight experience and task saturation as contributing factors.