AIRLINE PLT OPERATING IN THE GA ARENA FINDS IT IS NOT AS EASY AS IT LOOKS AND HAS A NEAR MISS WITH CLASS D AIRSPACE WHEN HE FAILS TO NAV PRECISELY.

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I DEPARTED WESTOSHA ARPT; WILMOT; WI (WI10); AT APPROX XA45 FOR DODGE CITY/JUNEAU ARPT (UNU) ABOUT 60 NM NNW. FSS WX BRIEF REVEALED VFR CONDITIONS ENTIRE RTE WITH OCCASIONAL AREAS OF VISIBILITY 4-5 MN IN HAZE. I WAS FLYING AT 3000 FT MSL USING GPS AND VOR/DME FOR NAV AND A VFR SECTIONAL FOR REF. WHILE N OF BUU VOR AND SE OF RYV RADIO BEACON I TURNED BAE VOR. I WAS SURPRISED TO SEE I WAS ONLY 7.5 DME FROM BAE AND TURNED IMMEDIATELY DUE W TO AVOID WAUKESHA ARPT'S CLASS D AIRSPACE WHICH HAS A CEILING OF 3400 FT. I WAS MONITORING WAUKESHA (UES) FREQ 123.7 AND HEARD TWR TALKING TO OTHER ACFT IN PATTERN. I NEVER HEARD A CALL FOR ME OR ANY UNKNOWN ACFT TRANSITING UES'S AIRSPACE. I AM VERY CONFIDENT I DID NOT INTRUDE ON UES'S AIRSPACE. HOWEVER; I'M SUBMITTING THIS AS A CLOSE CALL OR JUST IN CASE I'M WRONG. I HAVE NOT FLOWN FAR 91 FOR A WHILE. I FLY FOR A 121 CARRIER AND MOST OF MY RECENT 91 TIME HAS BEEN WITHIN 15-20 NM OF DEP ARPT. A NUMBER OF FACTORS CONTRIBUTED TO THIS CLOSE CALL: 1) INEXPERIENCED USING A VFR SECTIONAL; 2) INEXPERIENCE WITH AN OBS NAV. ALTHOUGH EASY TO USE I'M USED TO LOOKING AT AN RMDI WITH BEARING NEEDLES WHICH GIVE AN INSTANTANEOUS AND CONTINUAL DEPICTION OF POS FROM THE TUNED FACILITY; 3) ALTHOUGH VFR; HAZE DID CAUSE SOME MINOR PROBS IN RECOGNIZING GND FEATURES. I HAVE OBTAINED A STUDY GUIDE FOR VFR SECTIONAL INTERP; VIDEO TAPES ON AIRSPACE DIVISION; AND I'M ALSO REVIEWING AIM IN DEPTH AND GETTING BETTER ACQUAINTED WITH THE USE AND LIMITATIONS OF OBS NAV.