EMB-170 pilot crew reported a RA and NMAC while approaching Class B airspace. The PF followed the TCAS commands to avoid the intruder. ATC stated they were aware of the other aircraft.
Synopsis
EMB-170 pilot crew reported a RA and NMAC while approaching Class B airspace. The PF followed the TCAS commands to avoid the intruder. ATC stated they were aware of the other aircraft.
Narrative
While on the ZZZZZ Arrival flying west over the lake towards ZZZ (nearing the shoreline); Approach Control called out unidentified GA traffic to our 1:00; 500' above us. We were unable to spot the traffic however it appeared on our TCAS. It was flying opposite direction and proceeded to our 3:00. The traffic then turned and flew directly above us; descending to 400' above our altitude. It almost seemed to stop above our aircraft. Our TCAS initiated an RA (Resolution Advisory) and the Captain (Pilot Flying) immediately initiated a descent with power to idle and the boards out. I reported our descent to ATC due to an RA. The controller responded not to worry about climbing back up as he was just about to give us a lower altitude. The other aircraft then moved south (off our left side) and we proceeded without incident on the arrival; into the approach and landing on [Runway]. The Captain did an excellent job with his quick recognition and response. Controller and pilots were vigilant and doing their jobs. GA aircraft; whatever it was; did not seem aware that they were in an arrival flight path and very close to a commercial aircraft. Continue to educate people on regulations and flight safety to make them aware of the fact that they need to be vigilant and talk to ATC in traffic areas.
Second reporter narrative
ZZZ Approach issued a traffic alert of a GA VFR aircraft at 10;500'; we were assigned previously to maintain 10;000' 300 kts. As we began looking for traffic TCAS showed a target less than 10 miles from our aircraft and appeared to be tracking parallel to our path. The closure rate increased rapidly then we received a TA off of the aircraft. The aircraft seemed to be taking a perpendicular track to our flight path now. We received a RA with 'Monitor Vertical Speed'. I reduced the thrust to idle; deployed the speed brakes to full then disconnected the autopilot. My First Officer advised ATC we received an RA and ATC issued a descent when able. The conflict cleared as we reached 250 kts then we descended and reengaged the autopilot. The remainder of the flight continued as normal to our destination with no further issues. ATC was aware of type of aircraft; if they gave us more time to assess the crossing traffic we would have descended earlier. If altitude is less than 1;000' I always ask ATC to maneuver to keep a minimum of 5 miles from our aircraft.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.