LGT HAS A CONFLICT WITH AN SMA IN THE SNA ARSA.

Narrative

WE WERE BEING VECTORED FOR A VISUAL APCH BY APCH CTL TO RWY 19R; SNA. WE WERE GIVEN A DSCNT CLRNC FROM 5000 FT MSL TO 3000 FT AND A R TURN DIRECTLY AT THE LEMON OM (TO INTERCEPT THE LOC FROM LEMON WOULD BE A R 135 DEG TURN). I WAS HAND FLYING THE AIRPLANE THROUGH 3500 FT MSL AND DSNDING WHEN WE GOT A TCASII WARNING ON AN ACFT WITHIN 1 MI AT OUR 11 O'CLOCK POS AND 3000 FT. AT THE SAME TIME APCH CTL TOLD US ABOUT THE TFC. I IMMEDIATELY BEGAN A CLBING R TURN; LEVELING OFF AT 3800 FT MSL; HDG JUST INSIDE LEMON OM; WHICH SATISFIED THE TCASII ACTION REQUIREMENTS. THE CAPT OBTAINED VISUAL CONTACT WITH A SINGLE ENG ACFT AS IT PASSED UNDER US; L TO R. THE ACFT NEVER CHANGED ALT OR DIRECTION; AND HE CONTINUED SEBOUND; XING THE RWY 19R LOC PATH APPROX 3 MI FROM THE END OF THE RWY AT 3000 FT MSL. WHEN WE WERE WELL CLR OF THE CONFLICT WE TURNED TOWARD THE RWY AND RESUMED OUR DSCNT (AFTER BEING CLRED FOR THE VISUAL APCH; WHICH WE WERE NOT CLRED FOR PRIOR TO THE CONFLICT). IT WAS A SATURDAY AFTERNOON AND APCH CTL WAS VERY BUSY. HOWEVER; HIS TFC WARNING TO US WAS VERY LATE. THE ACFT WAS AT A HARD ALT (3000 FT) VFR; NOT TALKING TO APCH CTL OR THE SNA TWR. HE WAS ALSO INSIDE THE ATA. I WOULD ALSO ASSUME HE WAS NOT VISUALLY LOOKING FOR TFC; SINCE WE MUST HAVE 'FILLED' THE FRONT WINDSCREEN AS WE TRIED TO AVOID HIM; AND HE NEVER ALTERED HIS PATH OR ALT. HE DID HAVE AN ENCODING XPONDER. SNA NEEDS MORE AIRSPACE PROTECTION.