Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Confusion; Human-Machine Interface; Workload
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Weather / Turbulence
Flight Crew Became Reoriented; Flight Crew Executed Go Around / Missed Approach; Flight Crew FLC complied w / Automation / Advisory
Human Factors; Weather
During the flight to JAN there was a line of thunder storms that extended East to West.  There was a break in the storms and a report from ATC of a successful approach and landing at the airport.  Stayed high to avoid storms inbound and descent into the airspace was uneventful.  The approach course was within the break in the storms I was the pilot flying the pilot monitoring had loaded the full RNAV 34 approach.  After being cleared for the approach we got established on the inbound course.  Without notification the aircraft began a right turn.  Realizing that the aircraft had begun to turn we disconnected the autopilot and attempted hand flying the aircraft back onto course.  Realizing that I was descending I began to increase power and climb the aircraft.  In the descent a terrain warning aural alert sounded and a go around/missed approach was initiated.Storms in the area had created a very high work load. The turn was caused by a full procedure turn that had been included during the FMS setup for the approach that should not have been there.  The excessive descent was caused by a work overload for myself as the pilot flying. Proper training in non-standard / unusual approaches / non-precision approaches in low visibility conditions.
Air carrier First Officer experiences an unexpected right turn at the FAF on the RNAV approach to Runway 34 at JAN. The autopilot is disengaged and the reporter attempts to hand fly the approach which results in a terrain warning and a go-around. The next approach is successful.