Narrative:

We taxied into position on runway 24 and held for about 1 min before departing. From what we saw on the WX radar a 10-20 degree left turn to a heading of about 220-230 degrees would avoid thunderstorms. I discussed the heading we should fly with the first officer and so and we all agreed we would be able to avoid the storms with a 10-20 degree heading change. Once airborne, we asked departure control for a 20 degree turn to the left, which he approved. About 4 mi from the runway we could see on the radar that it was not going to be enough of a turn. I asked the first officer (who was handling the radio) to ask for a turn to the south. The controller was busy talking to other flts, so it was hard to ask him for a southerly heading. There was no way I was going to fly into the thunderstorm that lay directly ahead of us, so I turned to a 190 degree heading and leveled off at 4000 ft to avoid going into the dark clouds (our clearance was to 6000 ft). The controller told us he had not cleared us to make that large a heading change and told us to turn right. We told him we could not, because of the cell that was now passing off our right. In a couple of mins we were clear and told him we could turn right, which we did. The controller never did mention any conflict with traffic and we did not have any traffic on our TCASII.

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Original NASA ASRS Text

Title: DC10 FLC DEVIATES AROUND TSTM DEPARTING EHAM.

Narrative: WE TAXIED INTO POS ON RWY 24 AND HELD FOR ABOUT 1 MIN BEFORE DEPARTING. FROM WHAT WE SAW ON THE WX RADAR A 10-20 DEG L TURN TO A HDG OF ABOUT 220-230 DEGS WOULD AVOID TSTMS. I DISCUSSED THE HDG WE SHOULD FLY WITH THE FO AND SO AND WE ALL AGREED WE WOULD BE ABLE TO AVOID THE STORMS WITH A 10-20 DEG HDG CHANGE. ONCE AIRBORNE, WE ASKED DEP CTL FOR A 20 DEG TURN TO THE L, WHICH HE APPROVED. ABOUT 4 MI FROM THE RWY WE COULD SEE ON THE RADAR THAT IT WAS NOT GOING TO BE ENOUGH OF A TURN. I ASKED THE FO (WHO WAS HANDLING THE RADIO) TO ASK FOR A TURN TO THE S. THE CTLR WAS BUSY TALKING TO OTHER FLTS, SO IT WAS HARD TO ASK HIM FOR A SOUTHERLY HDG. THERE WAS NO WAY I WAS GOING TO FLY INTO THE TSTM THAT LAY DIRECTLY AHEAD OF US, SO I TURNED TO A 190 DEG HDG AND LEVELED OFF AT 4000 FT TO AVOID GOING INTO THE DARK CLOUDS (OUR CLRNC WAS TO 6000 FT). THE CTLR TOLD US HE HAD NOT CLRED US TO MAKE THAT LARGE A HDG CHANGE AND TOLD US TO TURN R. WE TOLD HIM WE COULD NOT, BECAUSE OF THE CELL THAT WAS NOW PASSING OFF OUR R. IN A COUPLE OF MINS WE WERE CLR AND TOLD HIM WE COULD TURN R, WHICH WE DID. THE CTLR NEVER DID MENTION ANY CONFLICT WITH TFC AND WE DID NOT HAVE ANY TFC ON OUR TCASII.

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.