Narrative:

Flight originated from collegedale airport (3m3). The purpose of flight was to test transmitting equipment in a robinson R-44 helicopter that is used for traffic reporting. There were 3 persons in the aircraft: myself as pilot, another commercial/CFI pilot, and the technician that would be performing the equipment test. I proceeded wbound from 3m3 to the location that the technician wanted to perform the transmitter test. The floor of class C airspace is 2600 ft over 3m3 so I was conducting this flight at 1500-1700 ft MSL. By referencing the current sectional chart for our area (atlanta), I determined that the test location was going to be 5.5 mi from the cha airport and that we would be staying just outside the surface area boundary and 1000 ft below the overlying class C airspace. The other pilot aboard agreed that it looked like we would be staying just outside class C surface area, so I opted not to contact cha approach control. We orbited over that location for 10 mins and then returned direct 3m3. On arrival at 3m3 unicom informed me that cha control tower had called and wanted to talk to me. I returned the call to the cha control tower and spoke with the tower manager. He said we were in fact only 3.5 mi from cha, not 5.5 like I had thought, and that I had entered their airspace by 1.5 mi. A subsequent check via GPS at the location we had been orbiting showed that I had indeed been within class C surface area by 1.5 mi. The cause of this airspace incursion was incorrect identify of my current location on the sectional chart and could have been avoided by a more careful examination of the chart and by following the good practice of contacting ATC whenever you are operating that close to controled airspace.

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Original NASA ASRS Text

Title: A ROBINSON R-44 HELI PLT HAS A CLASS C AIRSPACE INCURSION 3.5 NM E OF CHA, TN.

Narrative: FLT ORIGINATED FROM COLLEGEDALE ARPT (3M3). THE PURPOSE OF FLT WAS TO TEST XMITTING EQUIP IN A ROBINSON R-44 HELI THAT IS USED FOR TFC RPTING. THERE WERE 3 PERSONS IN THE ACFT: MYSELF AS PLT, ANOTHER COMMERCIAL/CFI PLT, AND THE TECHNICIAN THAT WOULD BE PERFORMING THE EQUIP TEST. I PROCEEDED WBOUND FROM 3M3 TO THE LOCATION THAT THE TECHNICIAN WANTED TO PERFORM THE XMITTER TEST. THE FLOOR OF CLASS C AIRSPACE IS 2600 FT OVER 3M3 SO I WAS CONDUCTING THIS FLT AT 1500-1700 FT MSL. BY REFING THE CURRENT SECTIONAL CHART FOR OUR AREA (ATLANTA), I DETERMINED THAT THE TEST LOCATION WAS GOING TO BE 5.5 MI FROM THE CHA ARPT AND THAT WE WOULD BE STAYING JUST OUTSIDE THE SURFACE AREA BOUNDARY AND 1000 FT BELOW THE OVERLYING CLASS C AIRSPACE. THE OTHER PLT ABOARD AGREED THAT IT LOOKED LIKE WE WOULD BE STAYING JUST OUTSIDE CLASS C SURFACE AREA, SO I OPTED NOT TO CONTACT CHA APCH CTL. WE ORBITED OVER THAT LOCATION FOR 10 MINS AND THEN RETURNED DIRECT 3M3. ON ARR AT 3M3 UNICOM INFORMED ME THAT CHA CTL TWR HAD CALLED AND WANTED TO TALK TO ME. I RETURNED THE CALL TO THE CHA CTL TWR AND SPOKE WITH THE TWR MGR. HE SAID WE WERE IN FACT ONLY 3.5 MI FROM CHA, NOT 5.5 LIKE I HAD THOUGHT, AND THAT I HAD ENTERED THEIR AIRSPACE BY 1.5 MI. A SUBSEQUENT CHK VIA GPS AT THE LOCATION WE HAD BEEN ORBITING SHOWED THAT I HAD INDEED BEEN WITHIN CLASS C SURFACE AREA BY 1.5 MI. THE CAUSE OF THIS AIRSPACE INCURSION WAS INCORRECT IDENT OF MY CURRENT LOCATION ON THE SECTIONAL CHART AND COULD HAVE BEEN AVOIDED BY A MORE CAREFUL EXAMINATION OF THE CHART AND BY FOLLOWING THE GOOD PRACTICE OF CONTACTING ATC WHENEVER YOU ARE OPERATING THAT CLOSE TO CTLED AIRSPACE.

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.