Narrative:

We were being vectored for an ILS runway 11R approach at msp. We had worked our way through a corridor from the west with our WX radar and the help of ATC. The airport was clear of thunderstorms. Our flight conditions at the time were clear with patchy clouds all around and these large wall of clouds to our left and straight ahead. It started with an assigned heading of 020 degrees. We were about to intercept 11R localizer 10-11 mi out. ATC advised us he was going to take us through the localizer, we suspected for spacing behind another aircraft. There was a large cell off the left side of our aircraft with a massive line 5 mi off the nose. The controller wanted us to turn left to a 220 degree heading. We told him we were unable due to the thunderstorm off our left side. He then gave us a heading of 360 degrees. We flew another mi or 2. We requested a turn to the right to keep us out of the large line ahead. The controller did not answer. We made 2 more calls with no answer. This is when I made the decision to make the turn. If I did not turn immediately, we would have flown into the large line. I turned to a 090 degree heading while the copilot announced on the radio we were making an emergency turn for WX avoidance. We monitored TCASII while not in contact with ATC. We made another call to ATC at which time another controller answered giving us a right 220 degree heading. He then cleared us for the approach. The remainder of the flight was uneventful. I tried calling ATC by phone but got no answer.

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Original NASA ASRS Text

Title: FLC OF LGT ACR ACFT DEVIATED FROM ASSIGNED TRACK DUE WX ENCOUNTER.

Narrative: WE WERE BEING VECTORED FOR AN ILS RWY 11R APCH AT MSP. WE HAD WORKED OUR WAY THROUGH A CORRIDOR FROM THE W WITH OUR WX RADAR AND THE HELP OF ATC. THE ARPT WAS CLR OF TSTMS. OUR FLT CONDITIONS AT THE TIME WERE CLR WITH PATCHY CLOUDS ALL AROUND AND THESE LARGE WALL OF CLOUDS TO OUR L AND STRAIGHT AHEAD. IT STARTED WITH AN ASSIGNED HDG OF 020 DEGS. WE WERE ABOUT TO INTERCEPT 11R LOC 10-11 MI OUT. ATC ADVISED US HE WAS GOING TO TAKE US THROUGH THE LOC, WE SUSPECTED FOR SPACING BEHIND ANOTHER ACFT. THERE WAS A LARGE CELL OFF THE L SIDE OF OUR ACFT WITH A MASSIVE LINE 5 MI OFF THE NOSE. THE CTLR WANTED US TO TURN L TO A 220 DEG HDG. WE TOLD HIM WE WERE UNABLE DUE TO THE TSTM OFF OUR L SIDE. HE THEN GAVE US A HDG OF 360 DEGS. WE FLEW ANOTHER MI OR 2. WE REQUESTED A TURN TO THE R TO KEEP US OUT OF THE LARGE LINE AHEAD. THE CTLR DID NOT ANSWER. WE MADE 2 MORE CALLS WITH NO ANSWER. THIS IS WHEN I MADE THE DECISION TO MAKE THE TURN. IF I DID NOT TURN IMMEDIATELY, WE WOULD HAVE FLOWN INTO THE LARGE LINE. I TURNED TO A 090 DEG HDG WHILE THE COPLT ANNOUNCED ON THE RADIO WE WERE MAKING AN EMER TURN FOR WX AVOIDANCE. WE MONITORED TCASII WHILE NOT IN CONTACT WITH ATC. WE MADE ANOTHER CALL TO ATC AT WHICH TIME ANOTHER CTLR ANSWERED GIVING US A R 220 DEG HDG. HE THEN CLRED US FOR THE APCH. THE REMAINDER OF THE FLT WAS UNEVENTFUL. I TRIED CALLING ATC BY PHONE BUT GOT NO ANSWER.

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.