PA31 ON BACK COURSE APCH CLR OF CLOUDS; LOOKING FOR ARPT; IS CONFUSED BY REVERSE SENSING AND DEVIATES E OF COURSE. CTLR CAUTIONED OF THE DEV AND VECTORED TO BACK ON COURSE. HAD ELECTED TO MAKE A GAR WHEN HAD THE PROB.

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IS THERE A REVERSE SENSING AREA TO THE SIDE OF A LOC COURSE? I WAS DOING THE LOC BACK COURSE APCH TO RNO RWY 34L. THE APCH HAD GONE FINE UNTIL I BROKE OUT OF THE CLOUDS; THEN I MESSED UP. I GOT TOO FAR TO THE R OF COURSE WHILE FLYING VISUAL AND LOOKING FOR THE ARPT. I JUST PLAIN BLEW IT. LESSON LEARNED: I ELECTED TO DO THE MISSED APCH. AFTER BEGINNING CLB WITH AN INITIAL CORRECTION TO THE L; THE CDI SWUNG OVER TO THE R. I CHANGED COURSE TO FOLLOW. THE NEEDLE OSCILLATED A COUPLE OF TIMES DURING THE CLB; AND THE NAV FLAG APPEARED ONCE OR TWICE; BUT FOR THE MOST PART I WAS GETTING A R 'FLY E' INDICATION WITH NO FLAG. ATC TOLD ME SEVERAL TIMES THAT I WAS WELL TO THE R OF COURSE. EVENTUALLY; THEY GAVE ME A VECTOR BACK TO THE L. I HAVE BEEN CHKING WHAT LOCS DO OFF COURSE SINCE THEN; AND I HAVE OBSERVED THAT THERE IS AN AREA TO SIDE OF COURSE WHERE THE CDI GIVES A FULL SCALE INDICATION TO FLY THE WRONG WAY. THIS IS LESS THAN 2 MI AWAY WHEN ABEAM THE ARPT. THERE IS NO NAV FLAG SHOWING WHEN IN THIS AREA; THE FLAG ONLY FLASHES BRIEFLY WHEN PASSING IN OR OUT OF THE ON-COURSE AREA OF GOOD SENSING. THERE IS USUALLY ALSO A GOOD AUDIBLE IDENT. I HAVE CHKED THIS USING 4 DIFFERENT LOC RECEIVERS IN 2 DIFFERENT ACFT ON LOCS AT RNO; SMF; AND OAK. I SUSPECT THAT I HAVE WATCHED LOCS DO THIS MANY TIMES BEFORE AND JUST NEVER THOUGHT ABOUT IT. IF LOCS DO THIS; IT SHOULD BE KNOWN TO PLTS. NONE OF MY COLLEAGUES KNOWS ABOUT IT. ADVISORY CIRCULAR 61-27C SAYS THAT IT IS NOT SUPPOSED TO HAPPEN. I THINK THAT IT WARRANTS A QUESTION ON THE INST WRITTEN TEST. PLEASE LET ME KNOW IF YOU FIND THAT I AM MISTAKEN. P.S. BACK COURSE APCH WAS MADE WITH HSI SET TO 164 DEGS. BACK COURSE CONFUSION WAS NOT THE PROB HERE.