B737-700
Flight Crew Air Transport Pilot (ATP)
Conflict Airborne Conflict
Flight Crew Took Evasive Action
Airport; Airspace Structure; Procedure
During the downwind leg of our 19R approach into SNA; I noticed several aircraft in the vicinity on TCAS. We descended from 5;000 down to 3;000 and were on an approximate heading of 360 when we were instructed by SoCal Approach to turn right to a heading of 130 (or close to it). I commented that it looked like he was going to turn us right into traffic; but it was initially hard to determine if we were closing on the traffic or following him. I was concerned but I thought the Controller knew what he was doing. About the time we rolled out on our heading we received a Traffic Alert following quickly by a Resolution Advisory to climb immediately. I disconnected the autopilot and tried to follow the commands but was distracted by the GA light twin aircraft that flew underneath our right side. It was close enough that I could see the pilot's sunglasses and the color of the aircraft. I believe we climbed approximately 300 FT. I'm not sure how far underneath us the other plane was; but I can say with certainty it was only a few hundred feet. The Captain immediately notified ATC of our situation and helped get us back into a stable flight situation (reconnected the autopilot; verified speed; heading and altitude etc). We resumed the flight; joined the localizer and landed without incident a few moments later.My concern is the VFR area just below the airspace and just north of SNA. After we landed; the Captain spoke with Socal Approach via telephone and was informed that they weren't certain the other aircraft was technically violating VFR airspace....though he may have been 'pushing the upper end of the corridor'. He also stated that they are boxed in by mountains so they have to keep us in tight for all 19R approaches into SNA. I filed this report to make everyone aware of two things: 1. - there is a potential for this to happen again in SNA (Or anywhere) and 2. - See and avoid is still ultimately our responsibility. (Everywhere).
A B737-700 flight crew suffered TCAS TA and RAs while on vectors for landing Runway 19L at SNA.