Narrative:

After notifying ATC of a need for a turn due to thunderstorm ahead, ATC delayed clearance to turn until only a left turn would avoid entering storm. A right turn clearance was approved very late and would have put aircraft into storm. The only action available was the left turn executed by PIC (PF). ATC did not respond to radio calls requesting earlier turn. Supplemental information from acn 212144: departure control then gave us a 30 degree left turn which I acknowledged with a request for a further left turn. Departure said he was unable because of traffic and I informed him that we were continuing to turn without clearance to avoid heavy radar returns. We continued left climbing turn until clear of WX then turned back right to a newly assigned heading. TCASII was a big help in looking for other traffic, no ATC TA's were received.

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Original NASA ASRS Text

Title: ACR DEVIATES FOR WX AFTER TOLD NO FURTHER DEV IN THAT DIRECTION. RADAR SHOWED SEVERE WX CELLS.

Narrative: AFTER NOTIFYING ATC OF A NEED FOR A TURN DUE TO TSTM AHEAD, ATC DELAYED CLRNC TO TURN UNTIL ONLY A L TURN WOULD AVOID ENTERING STORM. A R TURN CLRNC WAS APPROVED VERY LATE AND WOULD HAVE PUT ACFT INTO STORM. THE ONLY ACTION AVAILABLE WAS THE L TURN EXECUTED BY PIC (PF). ATC DID NOT RESPOND TO RADIO CALLS REQUESTING EARLIER TURN. SUPPLEMENTAL INFO FROM ACN 212144: DEP CTL THEN GAVE US A 30 DEG L TURN WHICH I ACKNOWLEDGED WITH A REQUEST FOR A FURTHER L TURN. DEP SAID HE WAS UNABLE BECAUSE OF TFC AND I INFORMED HIM THAT WE WERE CONTINUING TO TURN WITHOUT CLRNC TO AVOID HVY RADAR RETURNS. WE CONTINUED L CLBING TURN UNTIL CLR OF WX THEN TURNED BACK R TO A NEWLY ASSIGNED HDG. TCASII WAS A BIG HELP IN LOOKING FOR OTHER TFC, NO ATC TA'S WERE RECEIVED.

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.