Narrative:

I left shreveport, la (shv) and was cleared to join V94 climbing at 500 FPM, ATC told me I was southbound away from V94. Leveling off momentarily, I found my dg had precessed 90 degree. I had set the dg prior to takeoff to the runway heading. I reset the dg and proceeded on course. As long as I made gentle climbs and banks, less than standard rate, no precession occurred. However, in the initial en route phase I found the dg to not be in agreement with the magnetic compass by 15-20 degree every 3-4 minutes. Eventually, the dg settled down for the majority of the en route phase. When cleared for the visual approach and to land at williamson county airport runway 2, at about 14 DME, I was distracted by a large error between the dg and the magnetic compass. At the same time I had been tracking inbound on my VOR with a from flap presented. I changed the flag from a 'from' to a 'to' at the same DME, only to have the needle indicate I was right of course. I turned further left (west), the airport I saw was depicted similarly to williamson county as I all too quickly looked at the approach plate pictorial. As I reported landing I saw 36 on the runway. The williamson controller said 'not in sight' but I was already on short final. I did not see any other aircraft and proceeded to circle for landing while asking williamson county controller the frequency of carbondale tower. I circled and landed. In my disorientation and fixation on the erroneous dg and VOR reading, I neglected to cross reference with my secondary VOR and account for the 11 DME reading that I noticed immediately prior to landing. I am having the dg and VOR checked immediately. Personally, I plan on a more diligent cross reference of my navigation aids. I should not have relied on the dg and should not have changed the VOR flag. During VFR conditions while flying IFR I will track more carefully on my sectional chart.

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Original NASA ASRS Text

Title: PLT EXPERIENCES EXCESSIVE PRECESSION OF DIRECTIONAL GYRO. LEADS TO ATTEMPT TO LAND AT ARPT OTHER THAN INTENDED DESTINATION.

Narrative: I LEFT SHREVEPORT, LA (SHV) AND WAS CLRED TO JOIN V94 CLIMBING AT 500 FPM, ATC TOLD ME I WAS SBND AWAY FROM V94. LEVELING OFF MOMENTARILY, I FOUND MY DG HAD PRECESSED 90 DEG. I HAD SET THE DG PRIOR TO TKOF TO THE RWY HDG. I RESET THE DG AND PROCEEDED ON COURSE. AS LONG AS I MADE GENTLE CLIMBS AND BANKS, LESS THAN STANDARD RATE, NO PRECESSION OCCURRED. HOWEVER, IN THE INITIAL ENRTE PHASE I FOUND THE DG TO NOT BE IN AGREEMENT WITH THE MAGNETIC COMPASS BY 15-20 DEG EVERY 3-4 MINUTES. EVENTUALLY, THE DG SETTLED DOWN FOR THE MAJORITY OF THE ENRTE PHASE. WHEN CLRED FOR THE VISUAL APCH AND TO LAND AT WILLIAMSON COUNTY ARPT RWY 2, AT ABOUT 14 DME, I WAS DISTRACTED BY A LARGE ERROR BETWEEN THE DG AND THE MAGNETIC COMPASS. AT THE SAME TIME I HAD BEEN TRACKING INBND ON MY VOR WITH A FROM FLAP PRESENTED. I CHANGED THE FLAG FROM A 'FROM' TO A 'TO' AT THE SAME DME, ONLY TO HAVE THE NEEDLE INDICATE I WAS RIGHT OF COURSE. I TURNED FURTHER LEFT (WEST), THE ARPT I SAW WAS DEPICTED SIMILARLY TO WILLIAMSON COUNTY AS I ALL TOO QUICKLY LOOKED AT THE APCH PLATE PICTORIAL. AS I REPORTED LNDG I SAW 36 ON THE RWY. THE WILLIAMSON CTLR SAID 'NOT IN SIGHT' BUT I WAS ALREADY ON SHORT FINAL. I DID NOT SEE ANY OTHER ACFT AND PROCEEDED TO CIRCLE FOR LNDG WHILE ASKING WILLIAMSON COUNTY CTLR THE FREQ OF CARBONDALE TWR. I CIRCLED AND LANDED. IN MY DISORIENTATION AND FIXATION ON THE ERRONEOUS DG AND VOR READING, I NEGLECTED TO CROSS REFERENCE WITH MY SECONDARY VOR AND ACCOUNT FOR THE 11 DME READING THAT I NOTICED IMMEDIATELY PRIOR TO LNDG. I AM HAVING THE DG AND VOR CHECKED IMMEDIATELY. PERSONALLY, I PLAN ON A MORE DILIGENT CROSS REFERENCE OF MY NAVIGATION AIDS. I SHOULD NOT HAVE RELIED ON THE DG AND SHOULD NOT HAVE CHANGED THE VOR FLAG. DURING VFR CONDITIONS WHILE FLYING IFR I WILL TRACK MORE CAREFULLY ON MY SECTIONAL CHART.

Data retrieved from NASA's ASRS site as of August 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.