SCT CTLR DESCRIBES WORK ENVIRONMENT AND CLOSE SEPARATION ERROR AT 4000 FT.

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THIS INCIDENT OCCURRED APPROX 15 MI N OF SNA. THE WX WAS 1900 FT OVCST. THE ILS APCH WAS IN USE. THE ARR RATE WAS HIGH. I WAS WORKING THE SNA ARR SECTOR. I DID NOT HAVE A HDOF/ASSISTANT PLUGGED IN DUE TO STAFFING ISSUES. THESE ARE THE FOLLOWING COMPLICATIONS OF WORKING THE SNA ARR SECTOR: 1) HIGH TERRAIN TO THE E. THE MVA'S MAKE IT DIFFICULT TO GET THE ACFT DOWN IN A TIMELY ENOUGH MANNER TO TURN THEM ONTO THE FINAL FROM THE E; INSTEAD OF TAKING THEM ACROSS AND PUTTING THEM ON A R DOWNWIND. AND; YOU REALLY CANNOT USE THIS AIRSPACE TO THE E BELOW 5000 FT. 2) THERE ARE ESSENTIALLY ONLY 3 USABLE IFR ALTS (3000 FT; 4000 FT; AND 5000 FT). ON THE R DOWNWIND; IF YOUR TFC IS NOT SITUATED EXACTLY 3 MI W OF THE FINAL AND 1.5 MI FROM THE ADJACENT SECTOR TO THE W; YOU WILL HAVE AN OPERROR. WHEN THE SECTOR IS BUSY IT IS CHALLENGING TO KEEP ALL ACFT 3 MI OR 1000 FT APART (STANDARD IFR SEPARATION). 3) THE SECTOR IS EXTREMELY COMPACT. IT OWNS APPROX 15 MI OF AIRSPACE TO THE N; MAINLY DUE TO THE LAX FINAL. WHEN THE ARR RATE IS HIGH; YOU HAVE NOWHERE TO PUT THE ACFT. IF THE ARPT IS ADVERTISING ILS APCHS DUE TO WX; NOW YOU ARE FORCED TO MIX ALL SMALL ACFT WITH JET/TURBOPROP ACFT AND PUT THEM ON YOUR FINAL. WAKE TURB SEPARATION INCREASES THE SPACING ON FINAL. SO; FOR EXAMPLE; THE OPTIMAL FINAL COULD HOLD NO MORE THAN 5 ACFT. INSIDE THE OM; WE CAN GO DOWN TO 2.5 NM SEPARATION BTWN LIKE ACFT; THEN 3 MI SEPARATION OUTSIDE THE OM. THAT IS 5 LIKE ACFT ON THE FINAL; AS LONG AS THEY ARE ALL GOING THE EXACT SAME SPD; AND THERE ARE NO WAKE TURB ISSUES. NOW; LOOK AT A SCENARIO WITH A B757; AND A PA28. THE PA28 NEEDS 5 MI MINIMUM BEHIND THE B757. AND OBVIOUSLY; IF YOU HAVE A C172 DOING 100 KTS AND 5 JETS BEHIND HIM; EVEN SLOWED TO THE MINIMUM SPDS; YOU NEED AT LEAST 6-8 MI BEHIND THAT C172; BECAUSE OF THE CLOSURE RATE. I AM SURE YOU GET THE POINT. 4) YOU HAVE ACFT COMING INTO THE SECTOR FROM EVERY DIRECTION. THE JET/TURBOPROP ACFT COME INBOUND OVER KAYOH INTXN FROM THE E AT 5200 FT AND 190 KTS. SMALL ACFT FROM THE SE FOR SNA AT 5000 FT ON A VECTOR TO THE OM; OR ON A V363 RTE AT 5000 FT TRANSITIONING THE AIRSPACE. JET/TURBOPROP ACFT FROM THE SW ON A R DOWNWIND AT 5000 FT THAT SHOULD BE DOING 200 KTS BECAUSE THEY ARE UNDER CLASS B AIRSPACE. ALL SMALL ACFT DEPARTING SNA TO THE N VIA V363; V8; V21; LHS; CLBING NW OFF THE ARPT TO 3000 FT. YOU NEED TO GET THESE ACFT UP AND ON THEIR WAY THROUGH YOUR R DOWNWIND TFC THAT NEEDS TO DSND. FROM W OVER SLI LNDG SNA AT 4000 FT OR VIA V8 ROUTING AT 5000 FT. RECIPE FOR DISASTER; 5000 FT TFC IS ON CONVERGING COURSES; AND ACFT E OF SLI DROP OFF YOUR SCOPE FOR 30 SECONDS OR MORE DUE TO THESE ACFT FLYING INTO THE RADAR ANTENNAE MAIN BANG. FROM THE N YOU GET JETS INBOUND VIA V363 AT 4000 FT AND 210 KTS (IF YOU'RE LUCKY) AND THEY SHOW UP WITHOUT WARNING; PRACTICALLY RIGHT ON YOUR FINAL. ALSO; FROM THE N YOU GET SMALL ACFT LNDG LGB; FUL; AND TOA AT 4000 FT HDG S. YOU ALSO GET FUL DEPS LNDG SNA; GOING SE AND NE CLBING TO 3000 FT. NOW; LET ME DESCRIBE THE INCIDENT THAT OCCURRED WITH ACFT X AND A LEARJET INBOUND FROM THE N ON A V363 RTE AT 4000 FT AND 210 KTS. ACFT X WAS ON R DOWNWIND OUT OF 5000 FT FOR 4000 FT. THERE WAS A BE90 DOING E/W TURNS DROPPING FLIES AT 3500 FT VFR; INTERFERING WITH R DOWNWIND; R/L BASE AND THE FINAL. NORMALLY ACFT X WOULD HAVE BEEN DSNDED TO 3000 FT; BUT HAD TO STAY AT 4000 FT FOR THE BE90. POMONA SECTOR CALLED ME WITH A HDOF FROM THE N. I INSTRUCTED THE CTLR TO HAVE HIM FLY HDG 170 DEGS AND REDUCE SPD 170 KTS. AT THE TIME OF THE INSTRUCTION; THE LEAR APPEARED TO BE ON THE PRESCRIBED HDOF; WHICH WOULD BE OFF THE POM 164 DEG RADIAL. MY PLAN WAS TO EXTEND ACFT X ON DOWNWIND AND PUT THE LEAR ON FINAL AHEAD. I NOTICED THE LEAR HDG WBOUND; SO I CALLED POMONA SECTOR AND POINTED OUT ACFT X HDG 360 DEGS; AND ASKED; 'IS THAT LEAR TURNING?' AND AS I KEYED UP; THE CTLR WAS SAYING TO THE LEAR; 'EXPEDITE TURN.' AT THIS POINT IT BECAME APPARENT THAT THE LEAR WAS NOT ON THE CORRECT RTE/HDG. I CALLED TFC TO ACFT X; 1 O'CLOCK POS; 4 MI; TURNING SEBOUND; 4000 FT. POMONA SAID I COULD DSND THE ACFT X TO 3000 FT; SO I STARTED HIM DOWN. ACFT X GOT THE LEAR IN SIGHT AND I ADVISED THE PLT HE WOULD FOLLOW THAT TFC INBOUND TO THE ARPT AND TO MAINTAIN VISUAL SEPARATION WITH THAT TFC. AT THE TIME I BELIEVED I HAD VISUAL SEPARATION PRIOR TO LOSING STANDARD SEPARATION. I AM NOW SECOND-GUESSING THAT AND BELIEVE I MAY HAVE NOT HAD IT IN TIME. THIS INCIDENT OCCURRED BECAUSE OF A BREAKDOWN IN COM BTWN THE CTLRS. BE90 WAS A DISTRACTER; AND HAVING A HDOF THERE TO COORD AND A SECOND SET OF EYES COULD HAVE BEEN VERY HELPFUL. I HAD BEEN ON POS FOR APPROX 1 HR 15 MINS; WORKING MODERATE TO HVY TFC WITH A HIGH LEVEL OF COMPLEXITY. I AM NOT TELLING THIS STORY TO JUSTIFY WHAT HAPPENED; I AM TELLING THIS STORY SO THAT PLTS MAY GET A BETTER UNDERSTANDING OF WHAT WE ARE DEALING WITH ON THE ATC SIDE.