Commercial Fixed Wing
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Aircraft Equipment Problem Less Severe; Conflict NMAC
General None Reported / Taken
Human Factors
TA/RA on arrival. Flying the RAVEN6 arrival into BWI; we were level at 5;000 feet when a small aircraft flew beneath us. The aircraft showed to be 400 feet beneath us; and at that time the TCAS RA did not want us to maneuver.  Once we passed the traffic; we notified ATC and landed.
Air carrier Captain reported an NMAC during approach to BWI airport.