Narrative:

Is there a reverse sensing area to the side of a localizer course? I was doing the localizer back course approach to rno runway 34L. The approach had gone fine until I broke out of the clouds, then I messed up. I got too far to the right of course while flying visual and looking for the airport. I just plain blew it. Lesson learned: I elected to do the missed approach. After beginning climb with an initial correction to the left, the CDI swung over to the right. I changed course to follow. The needle oscillated a couple of times during the climb, and the navigation flag appeared once or twice, but for the most part I was getting a right 'fly east' indication with no flag. ATC told me several times that I was well to the right of course. Eventually, they gave me a vector back to the left. I have been checking 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 airport. There is no navigation 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 identify. I have checked this using 4 different localizer receivers in 2 different aircraft 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 pilots. 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 instrument written test. Please let me know if you find that I am mistaken. P.south. Back course approach was made with HSI set to 164 degrees. Back course confusion was not the problem here.

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Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.