Date: 201403
Local time of day: 1201-1800
Location: ZZZ.TRACON, US
Light: Daylight
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Descent
Airspace: Class C ZZZ
ATC / advisory: TRACON ZZZ
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Anomaly: Conflict NMAC
Detector: Automation Aircraft TA; Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Contributing factors: Airspace Structure; Human Factors; Procedure
Primary problem: Ambiguous

Narrative: At about ten minutes from landing; we were level at 4;000 feet when I noticed traffic on our TCAS at our one o'clock; six miles out; and four hundred feet above us. I was the pilot flying; and I asked the First Officer if he could see the traffic. I then noticed that the traffic was descending and flying towards us. I picked up the traffic visually at about three miles away which confirmed that it was on a possible collision course with us as it continued to descend into our altitude. By this time we had received a traffic alert from the TCAS. I disconnected the autopilot to begin an evasive maneuver. However; Approach Control mentioned the traffic and issued us a descent to 2;500 feet. I initially began the descent in hopes that we could avoid the traffic via ATC instructions. However; at that very moment; we received a TCAS resolution advisory (RA) to climb. I brought the throttles to almost maximum thrust and executed an aggressive climbing left turn (I made a decision to not only climb but to also climb away from the approaching aircraft). I felt that the bank and the aggressiveness of the maneuver were necessary to avoid the traffic. I do not believe we exceeded any limitations; including 2.5 G. The First Officer notified ATC of the RA. The last time I had visual contact with the traffic it was a little over a mile away. As it passed directly underneath us during our climb; it still showed red and zero zero (at our altitude) on the TCAS. As we approached 6;000 feet; we received the 'Clear of Conflict;' from the TCAS. We notified ATC of being clear of the traffic and the closeness of the near miss. ATC asked a couple of general questions; and we continued our descent. I engaged the autopilot; and transferred control of the aircraft to the First Officer. I called the Flight Attendant to make sure she was okay. She informed me that she was fine and was seated at the time of the event. Once at the gate; I made an announcement to the passengers to tell them that everything was fine; and I did my best to make the very noticeable maneuver during our arrival seem like a non-event. I called Maintenance Control to make sure we didn't need to have the aircraft inspected. After speaking to Maintenance; the Controller had me speak to Dispatch and we proceeded with a debrief. I really cannot think of an easy solution to events such as this. It would be nice if all aircraft in the vicinity an approach corridor to busy airports were required to be in contact with ATC.




Synopsis: While level at 4;000 feet during arrival; a CRJ200 Captain experiences a TCAS RA requiring a climb to 6;000 feet before a 'clear of conflict' is received.