Embraer Legacy 600 (EMB135BJ)
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Flight Instructor
Flight Crew Last 90 Days 45; Flight Crew Total 5500; Flight Crew Type 3500
Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude
Flight Crew Took Evasive Action
Human Factors; Weather; Airspace Structure
I was flying with passengers to ADS. While being vectored on the downwind into ADS at 3;000 MSL an aircraft closed on us from eleven o'clock. The target started at 600 FT below and climbed rapidly into us. The TCAS called a traffic alert then commanded a climb. I disconnected the autopilot; selected climb thrust and pulled the nose up; asking my pilot not flying to inform ATC that we were vacating our assigned altitude for an RA. He did and the Controller said no problem; calling out traffic a mile to the left (it was much closer than that). The RA continued until 4;000 FT before we received a 'clear of conflict'. I returned to my assigned altitude and landed without further event. We never saw the other aircraft as he was hidden by clouds. Based on radio transmissions I think the aircraft was a VFR Cessna that climbed to maintain visual conditions but was in the clouds when we passed him. The TCAS worked perfectly and crew coordination on the escape was excellent.
A TCAS RA on downwind at 3;000 FT for landing at ADS cause an EMB135 to take evasive action by climbing to 4;000 FT.