Air carrier flight crew reported descending and ultimately executing a go-around from an unstabilized approach after following guidance from a resolution advisory.
Synopsis
Air carrier flight crew reported descending and ultimately executing a go-around from an unstabilized approach after following guidance from a resolution advisory.
Narrative
ROBUC3 Arrival into Boston on Aircraft X; landing 4L and 4R; we were assigned the 4R ILS. We were told to look out for traffic and I assumed it was 4L traffic since it is known that clearance to land will not be given unless traffic on the parallel runway is in sight. The traffic we were told to look out for was actually at our 1 o'clock turning short final for 4R. Aircraft Y was in sight and we were told to follow. At 6000 ft. we wondered if they had forgotten about us since we were above the VNAV path. I asked the FO (First Officer) to inquire once there was a break in the radio chatter as it was a busy arrival time into BOS; but before we could get in they did indeed clear us to descend to 5000 ft. A bit later; we were cleared for the approach. On VNAV path; 1700 ft. was set for glideslope intercept and once inside the fix prior to the FAF; I armed the approach. The localizer captured. We were then told that there was traffic on the visual to 4L and to maintain visual separation. I kept an eye on the plane but it seemed to be coming closer; converging paths and descending upon us. We were then given a descending RA (Resolution Advisory). I clicked off autopilot and complied by the RA. Because it was visual conditions; I was confident in the safety of the flight in regards to the ground. The resolution alert then told us to monitor vertical speed" and wanted us to maintain altitude at 900 ft. We got a "glideslope" warning due to the RA descent on approach at the same time. Also at that exact moment; BOS Tower asked our intentions. My priority was keeping the flight director in the desired square of the RA guidance; as it was still fully present. The FO mentioned that he had missed the 1000-ft. call and I agreed that we should go around because we were fully configured; but not currently stable for the ILS that we were on. But even if he were to have made the 1000 call; I would not have done anything with that information due to complying with the RA. The plane was just below 900 ft. which is why the RA changed to guiding us to level off. Because I did not get the "clear of traffic" alert that I am used to hearing; I was still concerned about the traffic's position. I lost sight of the traffic while I was following the flight director intently. Due to the RA guidance being on for so long; not hearing "clear of traffic;" and having all of my surroundings visual with no terrain danger imminent; I decided to go into ALT (Altitude) hold mode not knowing exactly where the plane of conflict was. A hard go-around would more likely put us back into conflict with the aircraft and in an unsafe condition than staying level. Did the aircraft of conflict get an opposing RA? If they were climbing; our hard go-around would put us back in danger. We had lost sight of it; I was unsure of its location and chose what I thought to be the safest action. From there the clean-up was not perfect; but it was never unsafe. I called for flaps 2 too early; but corrected myself prior to the FO selecting them. We then sped up and proceeded to clean up and comply with BOS Tower's instructions. I do understand; per SOP; I incorrectly decided to do a soft go-around when company policy states the need for a hard go-around once under 1000 ft.; but this was NOT a standard situation and I made the call to deviate in the interest of safety. I also understand that we were supposed to initiate a go-around once at a dot deflection on the ILS; but since responding to the RA takes precedence; we were past that point. Again; this was not a standard situation. With the VMC conditions; I was fully aware of my location; altitude; and proximity to obstructions at all times and made flying the aircraft level a priority while we got our bearings with the converging traffic.I felt safe and confident in my decisions and control of the aircraft; even with everything that [was] happening in a tight timeline. They vectored us around to a visual to 4L and though I had asked my FO to set up the 4L RNAV for more visual guidance; I did not use it other than to see the extended navigation guidance to the 4L centerline. Once 4L was back in sight I asked for the flight director to be removed and I landed visually 4L.I think there should be a cadence for a soft go-around to help the flow of a nonstandard go-around clean-up. I think there should be a bit more of a review period for line checks on nonstandard flights rather than an immediate decision due to not following SOPs. I feel I did the safest thing regarding the situation given. Not knowing where traffic was and not knowing who may have been above us; doing a hard go-around with max thrust may have put us in a more unsafe position."
Second reporter narrative
I was pilot monitoring. The Captain; pilot flying; was receiving a line check on this leg from the Line Check Airman that was observing from the jumpseat in the cockpit.BOS ATIS was advertising ILS 4R and VA (Visual Approach) 4L approaches and departing Runway 9. We had the MCDU (Multipurpose Control Display Unit) set up for the ILS 4R and had briefed the approach and had barometric minimums set for ILS 4R. We had been cleared to descend via the ROBUC3 Arrival for Runway 4R; so we descended via the arrival to the bottom altitude of 6000 ft. We got handed off to the BOS Approach Controller and checked in with him. Then we were told to look for traffic at our 3 o'clock and 4 miles; west-northwest bound at 4500 ft.; type unknown; altitude indicated. Then we started to get above the VNAV PATH and wondered if the Approach Controller had forgotten about us. Then we were instructed to slow to 190 kt. Then we received clearance to descend and maintain 5000 ft. Aircraft Z was coming into BOS from the northwest and was told to look for us as his pair buddy at his 11 o'clock and 11 miles northeast bound 5600 ft. descending. Aircraft Z reported us in sight. Then we were instructed to reduce speed to 170 kt. and were cleared for the ILS 4R approach and the Approach Controller stated that we would have a pair buddy Aircraft Z landing left side; Runway 4L; and to maintain visual separation.I acknowledged cleared for ILS 4R approach and said we'd look for the other traffic - our pair buddy that would be landing on 4L. Then we were told to look for Aircraft Y traffic at our one o'clock and 5 miles at 3000 ft. and they told us that's who we were following. We spotted the traffic and reported Aircraft Y in sight; which was on a right base to final turn for Runway 4R. Then Approach told us to follow Aircraft Y and that we were cleared for the visual approach Runway 4R. Then; Aircraft Y was cleared for the visual approach Runway 4R ahead of us. Then Aircraft Z was instructed to descend and maintain 2500 ft. and turn left heading 100. Then; we were instructed to reduce speed to 150 kt. Then Approach asked Aircraft Z if they had us in sight at their 12 o'clock and 5 miles and they replied that they did. Then Approach told Aircraft Z to maintain visual separation with us and to report 4L in sight. Aircraft Z reported 4L in sight and acknowledged maintaining visual separation from us and then was told to join on his present heading and that should put him right behind us. Then Approach told us that Aircraft Z had us in sight and for us to maintain a visual at our 9 o'clock and 3 miles southeast bound at 3200 ft. I replied that we'd maintain a visual.We then received an RA (Resolution Advisory) with guidance to descend. The Captain descended per the RA descend guidance.Then we got handed off to Tower. I then reported to Tower that we got a traffic alert - and my report about the TCAS was delayed and I should have done it quicker and the Captain reminded me to report that - but what I should have said was that we got an RA with guidance to descend and I could have also requested a turn; similar to a PRM (Precision Runway Monitor) breakout; to avoid descending more since we were already fairly low. Tower replied and said; Roger. Advise clear." I was alternating my scan between outside windows/windshield looking for the traffic on 4L and between the PFD (Primary Flight Display) and MFD (Multi-function Flight Display) and because of that; I missed my 1000 ft. callout and we were at 860ft. when I looked to make that callout. I commented that we were low; full deflection below glideslope; and I believe the Captain commented unstable and I then announced; "Unstable; go-around;" and I believe we were at about 860 ft. I should have announced "unstable; go-around" quicker. The Captain proceeded with a soft go-around and requested ALT (Altitude) vertical mode and flaps 2. Since we were below 1000 ft. AGL; I should have replied with a suggestion to theCaptain to perform a hard go-around procedure per SOPs. The cadence of the standard callouts for the hard go-around would've helped us both; too; I believe. We were still at final approach speed and slow; so I did not put in flaps 2 because it didn't feel right to me because I knew we were slow. I should have verbalized to the Captain of why I wasn't putting in flaps 2 because we needed to first speed up and I should have suggested TOGA. It's true that I can't predict if they were immediately going to manually move the thrust levers forward as I was selecting the requested flaps 2; but it didn't feel right to me. Then the Captain quickly requested FLCH 210 on speed and requested gear up and flaps 2. I spun the speed bug up to 180; max for our present flaps setting; and selected flaps 2 and gear up. Then the Captain prompted me again for FLCH 210 once our flaps setting allowed for a higher airspeed.Then I reported unstable and requested a go-around to Tower. Tower said to go around and assigned runway heading and to climb and maintain 3000 ft. I acknowledged and then we were instructed to maintain 3000 ft. and to turn left heading 330. We climbed and turned as requested.Then we were handed off to BOS Departure. Then Departure told us to expect visual approach for Runway 4L. The Captain requested that I load the RNAV approach for Runway 4L in the MCDU and then requested that I extend a line off of the FAP (Final Approach Point). We were assigned a heading and cleared for the visual approach for Runway 4L. We configured for landing. The Captain used the PAPI for vertical guidance and had me turn off their flight director. The Captain did a great job of requesting the setup of the 4L approach and configuring for landing because it all happened quickly after the go-around and we didn't have much time to set up or time to pause.Then we were handed off to Tower again. I checked in with Tower on the visual approach for Runway 4L. Tower gave us clearance to land on Runway 4L. We encountered some wake turbulence during the landing and the Captain did a great job with that.Up until the go-around call and after the go-around; I feel it was a great flight from both the Captain and me.I used the wrong lingo when reporting the TCAS event to ATC. I said "traffic alert" instead of "RA" or "Resolution Advisory". I also should've done that traffic report to ATC quicker.I missed my 1000 ft. callout and should have been quicker with the unstable go-around callout. However; in my debrief with the Captain; they said even if I had called unstable go-around at 1000 ft.; they believe the RA descend guidance had us descending until 900 ft. 900ft. is when the RA cuts off and the RA guidance takes precedence; but we could've proceeded with the go-around immediately after the RA guidance disappeared.Although I don't recall pressing the preview button; I know I had vertical guidance when we were on the approach that I used to see if we were stable. I should've switched needles. In a situation like that where there were numerous traffic calls and ATC reports; I think hard tuning the localizer frequency would make sense in the future instead of autotuning when I anticipate that it's going to be extra busy and the opportunity to miss pressing preview.Recognizing our errors and reflecting on those to avoid them in the future; I also want to recognize our teamwork and the fact that the Captain prompted me for stuff I was delayed on; and I did not put in the flaps 2 they initially called for because we were slow. We both worked together in a very busy situation; with traffic on a base in front of us; and traffic on a base next to us; and then the RA with descend guidance; and then the go-around; followed by a visual approach without delay to a landing through some wake turbulence.Contributing factors: Division of duties; looking for Aircraft Y traffic on right base to final in front of us on Runway 4R; looking for Aircraft Z traffic on left baseto final next to us on Runway 4L; which the 4L traffic then caused the descending RA guidance.Suggestions: More effective and quicker communication from me as pilot monitoring with feedback to assist the pilot flying when they are juggling and processing a lot of tasks would be helpful. Although the Captain is pilot in command; I need to not hesitate to speak up about any feedback I have. Although I am second in command; we work as a team.Although we were juggling a lot; I need to be quicker when making RA notifications to ATC and when making unstable go-around callouts and reports to ATC."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.