A320
Flight Crew Commercial; Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 200; Flight Crew Total 2400; Flight Crew Type 1900
Conflict Airborne Conflict
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew FLC complied w / Automation / Advisory
Airspace Structure; Procedure
During our initial approach to SAT; descending via the LEMIG 1 arrival; ATC issued us an amendment to our altitude to be maintained (first we were assigned 10;000 FT then 11;000); that was due to traffic (small aircraft). When we leveled off at 11;000 FT first we had a TA; followed by a RA to level off. We executed the procedure as prescribed; it just took a couple of seconds. We didn't notify ATC of the conflict because we were out of it (the RA commanded us to level off; the traffic seemed not to be able to keep the altitude very well; it was like 400 FT below us). As additional information the autopilot was engaged. The rest of the flight continued without any further incident. One of the contributing factors I think was that ATC was a little bit busy managing other traffic; also the lack of precision from the small aircraft pilot to maintain the altitude as assigned.
A320 First Officer describes a TCAS RA descending into SAT at 11;000 FT. Leveling off was the required action to avoid a VFR small aircraft.