Date: 201808
Local time of day: 1801-2400
Location: ATL.Airport, GA
Flight conditions: VMC
Aircraft: Medium Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ATL
ATC / advisory: TRACON A80
Aircraft component: Turbine Engine
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Troubleshooting; Workload
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft TA; Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Overcame Equipment Problem
Contributing factors: Procedure; Human Factors; Aircraft
Primary problem: Ambiguous

Narrative: As we descended into ATL; we verified the arrival and the FO (First Officer) briefed an approach to runway 08L. After checking on with ATL Approach; we were assigned runway 10; which surprised us but was no big deal. We changed our landing runway; the approach; and the arrival in the [Flight Computer] and continued; verifying the arrival and re-briefing the approach.As we approached 11;000 feet; we noted a high LP engine vibration on the Number 2 engine (approximately 4.2 on the LP vibration monitor; which resulted in an amber indication); which was not a surprise to us based on a history of Number 2 engine vibration and the fact that there was an Engineering Authorization in the maintenance logbook as well. After consulting the QRH; the vibration reduced and turned back to green while we were downwind; about abeam the airport; without any pilot action to correct it. During this time; ATC cleared us to descend to 7;000 feet; and notified us to expect about an 8 mile final.As we descended; I noted in my head that it sounded like a pretty tight final for ATL and for our relative position; since we were abeam the airport on downwind at that time. I expected a slam dunk; but I didn't verbalize that with the FO; but I noted he was descending in FLCH; which indicated to me he had noticed it would be pretty tight too. The controller turned our base at about 8 miles; descended us to what I recall to be 3;000 feet and turned us to a 030 heading. The controller then told us to advise the field in sight. The FO began slowing the aircraft in anticipation of configuration. I was just about to do some mental math to see if we were high at this point; when the FO advised the field in sight.Simultaneously around the time we called the field in sight; we got a TCAS TA for an aircraft at our 10:00-11:00 position around the same altitude; were assigned a 070 heading; and I believe we may have been cleared for the approach at that time. As I read back the clearance; I scanned for the traffic; and discovered the traffic at about 11:00 moving to our 12:00; a few hundred feet below. The traffic appeared to be converging on us. I thought he was heading toward our flight path and had flown through the 09R approach course. The FO and I were both focused on the TA; and had not noticed the approach was not armed on the [Flight Computer]. I directed the FO to stop his descent; level off and queried ATC. I also instructed the FO to turn right back toward the final approach course; since I realized we had at this point flown through it because of our focus on the TCAS TA/scan for traffic. I'm honestly not sure how near the approach course we were when I first saw the other aircraft. I don't think we had yet flown through the final approach course; but it is possible we did. Everything happened very rapidly. We did unintentionally cross our final approach course. We never got an RA; however we did get within 600 feet vertically of the other aircraft.ATC gave us vectors back toward the final approach course; we rejoined it. Due to being high at this point; we elected to discontinue the approach and get vectors back for another approach; which went normally.There were several factors that led up to this event. To start; we were going to a runway we were less familiar with. It is much more common to land on the north or center runway complex in ATL when arriving from [the north] than the south complex.I was unnecessarily distracted during a high workload phase of flight by the engine vibration. That reduced my situational awareness once I returned from working the QRH. I was playing catch up; so I could be a good pilot monitoring during the approach.Even though the controller warned us it was going to be a tight approach; it is still difficult to configure for them because of the high speed ATL prefers. The FO did well trying to prepare for that; however it was another threat.The 65 degree intercept adjusted to 35 degrees by thecontroller when so close to the final approach course was another threat because it required immediate action; and one interruption can cause the chain to break; missing the approach clearance/arming the approach; furthermore; it was difficult for me to see the airport from my side of the aircraft to know how near the final approach course we were. Due to being distracted by the TA and visually acquired traffic; I also missed the 'localizer alive' call; as the pilot flying.Another factor was the high descent rate necessary to prepare for a stabilized approach. That descent rate was what triggered the TA in the first place; I think. If we had been less focused on trying to get down; we probably also would have noticed we didn't have the approach or LNAV armed on the [Flight Computer]; and the aircraft heading for 09L might have not appeared as if it was blundering toward us. It is very possible it was an optical illusion when I first saw the aircraft.There are several things I have already learned from this experience; and I intend to use them to prevent this from happening again. First; I will include in my threat forward section of our briefing that parallel approaches are a threat. It is something we would talk about extensively when briefing a PRM; but it was something we excluded unintentionally in a visual approach briefing. I'll also include how common it is to get approach clearances in ATL that leave you high and fast. It's not uncommon to use a non-standard configuration sequence (such as gear first) in ATL. Finally; I'll also brief a potential for a runway change and the pertinent information on the approach for the secondary approach to better prepare. Briefing each of these items will help set the stage for a successful approach.I should have been focusing more on our lateral course than our vertical path as well. That was an important part of my situational awareness that I unintentionally allowed to break down. I find it is best to often intercept a course in LNAV because the automation will do a much better job intercepting the course from a large angle intercept (such as 65 degrees) than the LOC function; and it's not uncommon to be distracted during the final approach course intercept phase of the flight because of radio chatter/high workload/etc. One tactic I personally use when I'm PF is keeping my hand on the glare shield with my finger near the LNAV or APPCH button on the intercept to these parallel approaches because I know it's not uncommon for aircraft to blunder through the final approach course.There are a few ways ATC could prevent instances like this too. It is far too common to be held up high in ATL; with an assigned speed that is rather fast. This increases the pilot workload dramatically. Earlier descents or longer final approaches would certainly help alleviate this. Additionally; a clearance something like 'turn right heading 070; join the runway 10 localizer; and advise the field in sight' might act as a barrier to unintentional blunders through the final approach course. Finally; concise controller radio use might also help during times of high traffic. I know it's not always possible; but there was a lot of radio chatter during this event; and it may have contributed to the timelines of everyone's reactions.




Synopsis: Air Carrier Captain reported overflying the final approach course due in part to a TCAS TA and discontinued the approach.