PLT OF AN AS350 HELI ON A FERRY FLT AT 500-1000 FT AGL ENTERS CLASS D AIRSPACE WITHOUT A CLRNC. HE TURNS AWAY FROM THE AIRSPACE AND IS THEN TOLD BY TRACON CTLR THAT HE MIGHT BE IN CLASS D AIRSPACE.

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I FERRIED AN AS350 HELI FROM DEN TO ABQ. THIS FLT WAS CONDUCTED UNDER FAR PART 91. LEAVING DEN; I REQUESTED TA'S FROM COS APCH CTL. THEY TOLD ME TO RPT 'ABEAM THE FRONT GATE.' WHEN I ADVISED THEM THAT I WAS NOT FAMILIAR; THEY TOLD ME TO LOOK FOR A B52 ON A POLE; WHICH I THOUGHT WOULD STAND OUT PRETTY WELL. I NEVER SAW THE B52; BUT I DID FINALLY SEE SOME SINGLE ENG CESSNA TFC; AND LATER; THE AIR FORCE ACADEMY ARPT. I ESTIMATE THAT I WAS ABOUT 2-3 MI AWAY WHEN I REALIZED I HAD TO BE IN THEIR AIRSPACE; AND BEGAN A TURN TO THE E. IN THE L TURN; I SAW A C172(?) ALSO TURNING L -- HE WAS ABOUT 1/2 MI AWAY FROM ME; TURNING BASE TO FINAL. I ALREADY HAD THE PUBLISHED FREQ FOR THE ACADEMY TWR ON THE COM #2 RADIO AND ADVISED I WAS APPROX 3 MI NNE AND TURNING E. THE PUBLISHED FREQ WAS APPARENTLY NOT THEIR MAIN TWR FREQ. THE ACADEMY TWR GAVE ME A NEW FREQ AT THE SAME TIME THAT COS APCH CHIMED IN WITH A TA; 2-3 O'CLOCK AND 1/2 MI. THIS WAS ANOTHER CESSNA IN THE PATTERN AT THE ACADEMY; AND WAS ALREADY PASSING BEHIND ME WHILE I TURNED TO 120 DEGS AS ADVISED BY THE APCH CTLR. APCH THEN ADVISED ME THAT I APPEARED TO BE IN THE AIR FORCE ACADEMY CLASS D AIRSPACE; WHICH I HAD ALREADY FIGURED OUT BY THEN. I NEVER DID CHANGE TO THE OTHER TWR FREQ; BY THEN IT WAS A MOOT POINT AS I HAD LEFT HIS AIRSPACE; AND HAD ALREADY FORGOTTEN IT IN THE EXICTEMENT. I WAS NAVING BY PILOTAGE USING THE DENVER TCA CHART. THE BUILT UP AREA; DEPICTED IN YELLOW ON THE MAP; DOES NOT EVEN COME CLOSE TO MATCHING WHAT IS ACTUALLY BUILT UP ON THE GND. TO A LOW LEVEL VFR PLT; THE EXTENT OF THE BUILT UP (CITY) AREA AND ITS SHAPE ARE VERY IMPORTANT NAV CUES. I HAVE FOUND THAT THE INFO ON THE VFR CHARTS IS OFTEN VERY INACCURATE AND OUT-OF-DATE IN RESPECT TO THE MAN-MADE FEATURES. THE DATA USED TO DEPICT ROADS; RAILROADS; CITY SIZE; CITY SHAPE; EVEN TWRS AND PWR LINES CAN BE YRS OUT-OF-DATE. IN FAST GROWING AREAS IN THE WESTERN UNITED STATES; THE VFR CHARTS ARE BADLY IN NEED OF AN OVERHAUL. THE PHX TCA CHART IS A PRIME EXAMPLE; AS APPARENTLY SO IS DEN.