Air carrier flight crew reported taking evasive action in response to a TCAS RA on arrival into IAD.
Synopsis
Air carrier flight crew reported taking evasive action in response to a TCAS RA on arrival into IAD.
Narrative
While being vectored for final to an ILS 01R at IAD; we received a TCAS Resolution Advisory (RA). We were on a perpendicular course to the ILS at 3000ft MSL abeam the intermediate fix MOSBY when the ATC Approach Controller advised of VFR traffic that was transiting at 2000ft MSL directly below our flight path. ATC then gave us a vector to intercept the localizer and maintain 3000 ft MSL. We quickly acquired the traffic on TCAS but were unable to visually identify the traffic. TCAS showed the traffic was climbing. The crew voiced concern about the traffic to each other and continued to fly the ATC clearance. The traffic conflict closed to within 600 ft vertical separation and the TCAS updated the traffic to a Traffic Advisory (TA). The traffic continued to climb and closed within 400 ft vertical separation and the TCAS updated the traffic to a RA. The crew quickly responded by disengaging the autopilot and auto-throttles and complying with the TCAS maneuver; climbing to avoid the traffic conflict. The PM (Pilot Monitoring) informed ATC that we were complying with an RA. We climbed no more than 700 ft from our given clearance. When the TCAS advised clear of conflict; we informed ATC. We intercepted the localizer and ATC cleared us the visual approach from our current position. We continued the approach and landed with no issue.
Second reporter narrative
During visual approach at IAD to at 3000 feet; Runway 1R; outside FAF; WAXIN; ATC advised VFR traffic at 2000 feet; that we saw on TCAS; eventually getting the TRAFFIC; TRAFFIC" oral warning that quickly evolved into a "CLIMB" RA to 3400 feet until clear of conflict. ATC was notified of beginning and end of RA maneuver; then we were cleared to land."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.