Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Type 2034
Situational Awareness
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Human Factors
While being vectored to join the localizer on the ILS for runway 24R in LAX; we were given a tight vector to join final and the FO (First Officer) felt it would be smoother/better to join final in NAV (magenta). The only problem was Vectors had not been activated in the FMS and the aircraft was unable to capture the final approach course so the aircraft flew through the 25L inbound course on the last assigned 220 heading at 2;100 feet. Realizing we were about to fly through the course but not knowing why exactly; I told the FO to keep turning the airplane in heading mode to rejoin while I glanced down at the box to double check we were tuned to the correct localizer frequency as well had loaded the correct approach in the FMS just to remove any doubt since we couldn't quite see the airport yet due to a scattered layer of clouds. Both of these things were correct.The FO had begun to turn us back north into the localizer but it wasn't enough so I took the aircraft from him and turned off the autopilot and began turning the aircraft immediately back into the localizer. It was at this time ATC asked us to turn 10 degrees right to rejoin the localizer and we told the Controller that we were in the process as well that we now had the runway in sight. ATC then cleared us the visual approach to runway 24R and the Controller asked if we were having issues picking up the localizer frequency. We told him no; but the aircraft did not capture it for some reason (at that point I hadn't realized the FO had tried to join the course in NAV mode) I hand flew the aircraft back over to the course and got it established. It was at this point I realized that LOC and GS were not armed on the FMA. I asked to FO to press the APP button and then the aircraft captured both localizer and glideslope I then transferred controls back to my FO. ATC told us to switch to LAX Tower and to have a good day from there; I believe all this happened within the span of about 30 seconds. We landed the aircraft normally without any other issues.If I had asked the FO on our downwind if he wanted me to activate vectors then the aircraft would have captured the course and we would not have gone through it. At the same time if the FO had armed APP instead of NAV we wouldn't have gone through it. I should have been more vigilant on checking which mode he was arming as well as double checking it had been successfully armed on the FMA; a habit I normally practice but must have been distracted with radio calls and searching for the runway outside in order to call the visual approach. Going forward; I will do 2 things to prevent this in the future. First; I will do my best to remember to always activate vectors so that it mitigates any chance of passing through the localizer course either in NAV or APP. Second; I will be more vigilant about checking the FMA to ensure myself as well as my FO's have armed the appropriate modes.
EMB-175 Captain reported overshooting the final approach course to LAX due to improper mode selection during FMS setup.