SMA HAS NMAC WITH COMMUTER ACFT.

Narrative

VFR FLT IN C-182; LEVEL AT 7500 FT MSL; INBOUND TO RZS ON COURSE 115 DEGS; 11 DME; 150 KTS GND SPD. I WAS RECEIVING FLT FOLLOWING FROM VANDENBURG APCH ON 118.0. SUN HAD SET (AT 7500 FT) APPROX 15 MINS PRIOR. ALL NAV; STROBE; AND BEACON LIGHTS WERE ON. WX WAS CLR AND 30 MI VISIBILITY; A HAZE LAYER BELOW STARTED AT APPROX 6000 FT MSL AND REDUCED VISIBILITY TO 8-10 MI. NO WARNING FROM VANDENBURG. SUDDENLY; A COMMUTER TWIN ENG AIRLINER APPEARED AT APPROX 11 O'CLOCK; PLUS 200 FT VERTICALLY; AND APPROX 225 FT IN FRONT OF ME. (HE WAS DSNDING INTO SANTA BARBARA.) THE AIRLINER CONTINUED TO DSND IN FRONT OF ME. I TURNED R AND DSNDED. WHEN I FELT THERE WAS NO LONGER A COLLISION DANGER; I WAS ON COURSE 150 DEGS AND HAD DSNDED TO 7300 FT. THE AIRLINER NEVER MANEUVERED. AFTER THE AIRLINER WAS WELL IN FRONT OF ME AND BELOW; I CLBED AND RESUMED COURSE FOR SAN MARCUS PASS. THE AIRLINER CONTINUED TO DSND OVER THE RIDGE INTO SBA. AS I WAS RETURNING TO COURSE; VANDENBURG HANDED ME OFF TO SANTA BARBARA (125.4). BEFORE I LEFT THE FREQ; I QUERIED THE CTLR AS TO WHETHER OR NOT HE HAD SEEN THE AIRLINER THAT HAD NEARLY HIT ME. HE SAID NO; BUT MENTIONED THERE ARE KNOWN RADAR DIFFERENCES IN THE LAKE CACHUMA AREA. I CONTINUED WITH SANTA BARBARA APCH; AND THEN HOME. AFTER LNDG I VERIFIED THAT ALL OF MY LIGHTING SYS WERE OPERATIONAL. THE NEXT DAY; I RPTED TO THE LCL FSS AN NMAC. WHILE IT IS MY RESPONSIBILITY TO SEE AND AVOID OTHER TFC; I ALWAYS THOUGHT THAT PARTICIPATING IN FLT FOLLOWING WOULD PROTECT ME FROM IFR TFC (OR PROTECT IFR TFC FROM ME; WHICH IS THE SAME THING). OBVIOUSLY; I WAS WRONG. AS THE AIRLINER IN QUESTION WAS NOT TALKING TO VANDENBERG APCH; I WONDER IF THERE IS NOT AN ATC COORD PROB IN THIS AREA. I SHOULD HAVE BEEN HANDED OFF TO SBA; OR THE AIRLINER SHOULD HAVE BEEN TALKING TO VANDENBERG. EVERY ACFT HAS A BLIND SPOT FOR VISIBILITY. IN A CESSNA 182; YOU CANNOT SCAN FOR TFC ABOVE AND BEHIND YOU. SEE AND AVOID IS A COOPERATIVE CONCEPT. IT MAY BE THAT SBA SAW ME ON RADAR AND CHOSE NOT TO CALL TFC TO THE AIRLINER DUE TO ALTIMETER SETTING DIFFERENCES. THIS IS FURTHER SUPPORT FOR POINT #2; THEREBY INSURING COMMON ALTIMETER SETTINGS. KNOWN RADAR DEFICIENCIES SOUND LIKE A PROB THAT SHOULD BE FIXED. THE VAN CTLR (AND OTHERS) MENTIONED REFLECTIONS OFF THE LAKE AS A PROB. THIS IS EASILY (TECHNICALLY; NOT BUDGETARILY) REMEDIED BY INSTALLING ANOTHER RADAR FACILITY IN THE VALLEY NEAR THE LAKE AND PERFORMING SOME ERROR CHKING ON THE TRACK FILES. (I AM AN AERONAUTICAL AND ELECTRICAL ENGINEER WITH RADAR EXPERIENCE.) THIS WOULD EASILY REMEDY MULTIPATH EFFECTS. THE CREW OF THE AIRLINER EITHER DIDN'T SEE ME OR SOMEHOW MISJUDGED MY PROX. I SUSPECT THE FORMER; AS NO EVASIVE ACTION WAS EVER TAKEN BY THE AIRLINER. THIS MIGHT HAVE BEEN CAUSED BY COCKPIT DISTRS. ONLY THE CREW OF THAT ACFT KNOWS. CREWS OPERATING ON IFR FLT PLANS IN VMC; I FEEL; MUST TAKE THE TIME TO SCAN IN FRONT OF THEM; AND SHOULD BE MADE AWARE WHEN OPERATING IN AREAS OF KNOWN RADAR PERFORMANCE DIFICIENCIES.