Narrative:

While descending into the sdf area we encountered several small thunderstorm cells requiring deviation. I advised center that we would need a 20 degree course change to the right for the WX. The controller stated 'deviation approved, cleared direct to ksdf when able.' as we turned right, it became obvious that further deviation was imminently necessary, so we continued our right turn to approximately 90 degrees right of course. When we rolled out on the new heading, ATC asked us what our heading was -- then stated that we were only approved for a 20 degree deviation and that there was other traffic in the area we were turned towards. At this time we were clear of the WX and turned direct to sdf as previously cleared. I feel we could have better handled the situation if we had kept the controller informed of our intentions to continue our deviation. We had no choice but to deviate to avoid the cells. Supplemental information from acn 303936: as we descended the thunderstorm grew in intensity and we encountered rain, turbulence, and static on the radio. With so much static on the radio we could not communication, and with turbulence and rain, we only wanted out of the bad WX. In the future I will ensure that we advise ATC well in advance when large deviations might be necessary.

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Original NASA ASRS Text

Title: A DC-8 FLC REQUESTED A 20 DEG DEV, BUT REQUIRED A 90 DEG DEV, WHICH WAS TAKEN. ATC INTERVENED AS ACR TRACK BECAME A POTENTIAL CONFLICT.

Narrative: WHILE DSNDING INTO THE SDF AREA WE ENCOUNTERED SEVERAL SMALL TSTM CELLS REQUIRING DEV. I ADVISED CTR THAT WE WOULD NEED A 20 DEG COURSE CHANGE TO THE R FOR THE WX. THE CTLR STATED 'DEV APPROVED, CLRED DIRECT TO KSDF WHEN ABLE.' AS WE TURNED R, IT BECAME OBVIOUS THAT FURTHER DEV WAS IMMINENTLY NECESSARY, SO WE CONTINUED OUR R TURN TO APPROX 90 DEGS R OF COURSE. WHEN WE ROLLED OUT ON THE NEW HDG, ATC ASKED US WHAT OUR HDG WAS -- THEN STATED THAT WE WERE ONLY APPROVED FOR A 20 DEG DEV AND THAT THERE WAS OTHER TFC IN THE AREA WE WERE TURNED TOWARDS. AT THIS TIME WE WERE CLR OF THE WX AND TURNED DIRECT TO SDF AS PREVIOUSLY CLRED. I FEEL WE COULD HAVE BETTER HANDLED THE SIT IF WE HAD KEPT THE CTLR INFORMED OF OUR INTENTIONS TO CONTINUE OUR DEV. WE HAD NO CHOICE BUT TO DEVIATE TO AVOID THE CELLS. SUPPLEMENTAL INFO FROM ACN 303936: AS WE DSNDED THE TSTM GREW IN INTENSITY AND WE ENCOUNTERED RAIN, TURB, AND STATIC ON THE RADIO. WITH SO MUCH STATIC ON THE RADIO WE COULD NOT COM, AND WITH TURB AND RAIN, WE ONLY WANTED OUT OF THE BAD WX. IN THE FUTURE I WILL ENSURE THAT WE ADVISE ATC WELL IN ADVANCE WHEN LARGE DEVS MIGHT BE NECESSARY.

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.