Airbus 318/319/320/321 Undifferentiated
Confusion; Situational Awareness; Time Pressure; Workload
ATC Issue All Types; Conflict NMAC; Deviation - Altitude Excursion From Assigned Altitude
Flight Crew Became Reoriented; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Human Factors; Procedure
At 5000 MSL feet; approximately 10 miles west of SLI VOR; SoCal Approach assigned us a left turn to a heading of 050 degrees. The Captain initiated the turn with the autopilot engaged. Approximately 15-20 degrees into the left turn; SoCal Approach quickly cleared us back to our original heading. As the aircraft was in the right turn back to approximately 070 degrees; we received a resolution advisory (RA) directing a climb; as it appeared that an aircraft was in close proximity to us at approximately 500' below our assigned altitude. The captain immediately followed the RA direction and began to climb; and I promptly notified SoCal Approach that we were responding to a RA. At approximately 5500 MSL feet; the RA indicated a level off. A few seconds later; we received a subsequent RA directing another climb; however; it now it appeared that the aircraft was 300' directly beneath us. At approximately 5700' MSL; the RA indicated that we were clear of the conflict. The captain returned to the previously assigned altitude of 5000' MSL and I notified SoCal Approach accordingly. SoCal approach never made any mention of any traffic or the RA event. Also; we never saw the offending traffic during the RA event. We continued and landed uneventfully.
An air carrier pilot reported a TCAS RA CLIMB during a near miss with an unidentified aircraft at about 5;500 feet near SLI .