Date: 201908
Local time of day: 1201-1800
Location: ZZZ2.Airport, FO
Flight conditions: VMC
Light: Daylight
Aircraft: A319
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
ATC / advisory: Center ZZZ2
Aircraft component: FMS/FMC
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Distraction; Situational Awareness; Human-Machine Interface
Second reporter function: Captain; Pilot Not Flying
Anomaly: Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance
Contributing factors: Human Factors; Procedure; Aircraft
Primary problem: Human Factors

Narrative: I was PF (Pilot Flying) into ZZZ; an airport I have been to very infrequently; perhaps a total of 6 times; the most recently being at least 6 months ago. Our clearance was the ZZZZZ Arrival; which is runway-dependent in the sense that there is a ZZZZZ landing both east and west. The ATIS was advertising the ILS/Visual to XXL and RNAV/Visual XXR; as the ILS XXR was NOTAM'ed out-of-service. Because we were approaching ZZZ from the south; the FMS was programmed with the ILS XXL. However; upon initial contact with Arrival (Approach) Control; we were assigned XXR and the FMGC (Flight Management Guidance Computer) was changed to RNAV XXR. I confirmed this before it was executed and then proceeded to independently verify the STAR's speeds and altitudes were still correct. Not only was this taking place below 10;000 ft.; ATC began to get busy and a light twin appeared on TCAS approximately 2;000 ft. below our nose. We visually acquired the aircraft and not long thereafter; ATC issued us an immediate right turn and instructed a level-off. I assumed this was to prevent a traffic conflict with the aforementioned light-twin until ATC stated that our clearance limit was the ZZZZZ and we had NOT been cleared for the RNAV. It was then I realized my gross error. In loading the second approach; the RNAV XXR had auto-strung and I failed to catch that we should not have allowed that to happen. Contributing factors: I have been flying to ZZZ quite a bit this summer and executing RNAV approaches that we do auto-string. I believe this led to an expectation bias. Also; the first approach loaded (the ILS) had not auto-strung; so I was not in the mental mode to be 'on the lookout' for it. My attention was also distracted with attempting to visually acquire the light twin. But the bottom line is this is instrument flying and I did not catch my mistake until it was pointed out to me.


Second narrative: On a day VFR southern arrival into ZZZ we were cleared to descend and maintain 12;000 ft. at ZZZZZ1 on the ZZZZZ arrival Runway XX. Several minutes later on the approach we were told to slow to 250 knots early; instead of the planned 280 at ZZZZZ1. We asked for relief at ZZZZZ1 at 12;000 ft. since we were about 10 miles away speed 320 knots. We were given relief and cleared for the speed first and altitude second which we complied with. I believe we made the crossing restriction regardless. Next we were cleared to a lower altitude several times and the RNAV Runway XXR which required us to change runways from the expected ILS XXL and then continue the arrival. There was then a missed radio call to the final approach controller which was resolved and then an ATC-directed heading change and climb back up to 5;500 ft. from about 5;200 ft. for VFR traffic. Somewhere in the compressed time and confusion of multiple changes in heading; altitude; speed; runways and VFR traffic; I missed the fact that the FMGC (Flight Management Guidance Computer) had auto-strung the arrival to the final approach with full continuity. The First Officer flying verbalized the continuity on the approach; she actually said the word auto-strung; and I responded OK but was overloaded and didn't really catch what she said. She was hand flying the aircraft at this point and followed the flight director onto a left base turn for the final approach before we were actually cleared for the approach. The controller caught the error and had us turn immediately back to the downwind on a 080 or 090 heading before we were then vectored a few miles later to turn base behind a 787. I don't believe there was any traffic conflict because the controller caught our error promptly and we complied with his commands immediately as we then recognized our mistake. The rest of the arrival and landing was normal and uneventful; but basically our error was a left base turn to final for the approach before we were cleared to do so.


Synopsis: A319 Flight Crew reported an automation mismanagement resulting in a course deviation.