PA28 PLT CHALLENGES SCT APCH CTLR WHEN CTLR CLAIMS THE PLT IS NOT AT THE CORRECT FIX FOR DSCNT WHEN CONDUCTING THE LDA RWY 19 APCH TO SNA.

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I WAS CLRED FOR; AND ESTABLISHED ON; THE LDA APCH TO SNA. THE WX WAS VMC. UPON PASSING EFFIE (LOC DME 10.2); I DSNDED TO THE MINIMUM ALT (1600 FT) FOR THE NEXT NAV FIX; TUSTI. SHORTLY AFTER LEVELING OFF AT 1600 FT; THE CTLR ASKED ME FOR MY POS; WHICH WAS AROUND 8 DME. SHE RESPONDED THAT SHE SHOWED ME JUST OUTSIDE OF EFFIE; BELOW THE MINIMUM ALT FOR THE SEGMENT; AND SUGGESTED THAT I CLB TO 2000 FT. I COMPLIED; BUT NONETHELESS; REMAINED CERTAIN THAT I WAS; IN FACT; WHERE I HAD RPTED. I HAD DOME INFO AS WELL AS BACK-UP POS CONFIRMATION PROVIDED BY MY SEQUENTIAL SELECTION OF THE SLI 058 DEG AND 080 DEG RADIALS ON MY #2 VOR; WHICH SHOWED ME THAT I HAD PASSED EFFIE BUT HAD NOT YET REACHED TUSTI. UPON REACHING TUSTI; I WAS HANDED OFF TO THE TWR AND COMPLETED THE APCH WITHOUT INCIDENT. THE NEXT DAY; I DECIDED TO TELEPHONE SOCAL APCH AND TRY TO FIND THE REASON FOR THE DISCREPANCY. THE CTLR WAS AWARE OF THE SIT AND SUGGESTED THAT I SPEAK WITH THE PERSON WHO HAD HANDLED MY APCH. HE PUT HER ON THE PHONE AND; IN THE COURSE OF OUR THOROUGH REVIEW OF THE EVENT; SHE DETERMINED THAT THE STRONG SIMILARITY OF THE DISTANCE TO THE RWY OF THE RESPECTIVE NAV FIXES FOR THE LDA AND THE NDB RWY 19R APCHS GREATLY INCREASED THE PROBABILITY THAT CTLRS COULD ERRONEOUSLY APPLY THE NDB FIXES TO THE LDA APCH. SHE ACKNOWLEDGED THAT THIS IS WHAT SHE HAD DONE DURING MY APCH AND EXPRESSED A DETERMINATION TO SEEK A CHANGE IN PROC TO PREVENT THIS FROM HAPPENING IN THE FUTURE. THE ERROR DID NOT POSE A DANGER TO ME BECAUSE THE SEGMENT MINIMUM ALTS FOR THE NDB APCH ARE HIGHER THAN THOSE FOR THE LDA APCH. THE BEST PART OF THIS ENTIRE EXPERIENCE FOR ME WAS THE NATURE OF MY EXCHANGES WITH THIS CTLR; BOTH DURING THE APCH ITSELF AND; IN PARTICULAR; AFTERWARD ON THE TELEPHONE. SHE WAS NOT DEFENSIVE AND CONDUCTED HERSELF IN SUCH FASHION AS TO CONVEY HER DESIRE TO DETERMINE THE CAUSE OF THE CONFUSION THAT OCCURRED DURING MY APCH. SHE ACCEPTED RESPONSIBILITY FOR THE EVENT AND APOLOGIZED FOR HER ERROR. AS A RESULT; I WILL FUNCTION MORE EFFECTIVELY WITHIN THE ATC SYS.