Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 102
Communication Breakdown
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude
Flight Crew FLC complied w / Automation / Advisory
Procedure; Human Factors
Descending into ZZZ; we received an RA from a VFR traffic crossing our path below us at approximately 5;500 ft. MSL. We were descending to initially 3;000 ft. MSL to setup for landing on Runway XX (VMC conditions prevailed and the ATIS advertised a visual to Runway XX); but then were told to maintain 6;000 ft. MSL by Center for VFR traffic she was not talking to in our path. Hearing and seeing this scenario develop we shallowed our descent rate to level at 6;000 ft. MSL in an attempt to mitigate a predictive RA scenario. Once level and seeing the traffic was continuing in our direction; we also attempted a turn to avoid the traffic prior to the RA; however the frequency was congested and the turn was too late. Once we received permission to turn and initiated it; we ended up receiving the RA. We complied with the RA; disengaged the autopilot; and also climbed to approximately 6;500 ft. MSL to avoid the traffic showing at one point 400 ft. below us and advised Center of the RA. We were given permission to climb and; once clear of the conflict; to proceed to ZZZ without further issue.The event occurred due to a few factors coming together. The main issue is that the VFR aircraft was maneuvering without talking to ATC so as to avoid traffic. It was also a beautiful day; so there was a lot of GA aircraft the Controller was working with causing the frequency to become very congested. Secondly; the Controller should have issued us a vector or higher altitude to maintain to avoid the traffic as we never had or called aircraft in sight. We could have tried to turn earlier; but the congestion on the frequency prevented this from happening as well.I feel that this issue could have been prevented had the Controller issued us a higher level off altitude; or given us a vector once it was determined that the VFR target could become an issue. I feel that we tried our best to avoid this scenario by shallowing our descent and even requesting a turn. It just came down to the VFR traffic had an unpredictable flight path; the frequency was very congested; and once we received our clearance to turn it was too late.
First Officer of a CRJ-200 reported an RA while descending towards destination and cited the large amount of GA aircraft in the area as a contributing factor.