Narrative:

Inbound to atl on the la grange arrival, ATC issued 090 degree vector. WX was VMC with twring cumulus buildups. I began turn with autoplt, using heading bug from approximately 030 degrees to 090 degrees. As aircraft was coming around I saw that heading would take us through a cumulus build-up. I slewed the heading bug further to about 120 degrees to continue the turn, and then when I knew we would clear the build-up, I returned the heading bug to 090 degrees. The aircraft heading reached approximately 110 degrees before reversing direction. ATC then called and asked our heading. The first officer replied 'returning to 090 degrees after a short deviation.' ATC was not happy and said we need to tell him before deviating because departing traffic is right there climbing through our altitude. The deviation of 20 degrees or so for only a mi or 2 did not seem like enough to be noticed. With ATC frequency congestion it is almost impossible to request small deviations in a timely enough manner. Also if arrival and departure procedure charts contained some information on airspace architecture it may help prevent transgressions into bordering airspace.

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Original NASA ASRS Text

Title: A CARJ CAPT DEVIATED, WITHOUT PERMISSION, AROUND TWRING CUMULUS IN A80'S AIRSPACE CAUSING A POSSIBLE SEPARATION ISSUE.

Narrative: INBOUND TO ATL ON THE LA GRANGE ARR, ATC ISSUED 090 DEG VECTOR. WX WAS VMC WITH TWRING CUMULUS BUILDUPS. I BEGAN TURN WITH AUTOPLT, USING HDG BUG FROM APPROX 030 DEGS TO 090 DEGS. AS ACFT WAS COMING AROUND I SAW THAT HDG WOULD TAKE US THROUGH A CUMULUS BUILD-UP. I SLEWED THE HDG BUG FURTHER TO ABOUT 120 DEGS TO CONTINUE THE TURN, AND THEN WHEN I KNEW WE WOULD CLEAR THE BUILD-UP, I RETURNED THE HDG BUG TO 090 DEGS. THE ACFT HDG REACHED APPROX 110 DEGS BEFORE REVERSING DIRECTION. ATC THEN CALLED AND ASKED OUR HDG. THE FO REPLIED 'RETURNING TO 090 DEGS AFTER A SHORT DEV.' ATC WAS NOT HAPPY AND SAID WE NEED TO TELL HIM BEFORE DEVIATING BECAUSE DEPARTING TFC IS RIGHT THERE CLBING THROUGH OUR ALT. THE DEV OF 20 DEGS OR SO FOR ONLY A MI OR 2 DID NOT SEEM LIKE ENOUGH TO BE NOTICED. WITH ATC FREQ CONGESTION IT IS ALMOST IMPOSSIBLE TO REQUEST SMALL DEVS IN A TIMELY ENOUGH MANNER. ALSO IF ARR AND DEP PROC CHARTS CONTAINED SOME INFO ON AIRSPACE ARCHITECTURE IT MAY HELP PREVENT TRANSGRESSIONS INTO BORDERING 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.