Narrative:

Flight proceeding en route from HHH to clt. Via direct flo when ATC cleared our flight to turn left to heading of 300 degrees and descend out of 15000 to an altitude of 11000 ft. While descending through 14300 ft we were given an order by ATC to climb immediately to 15000 ft. ATC then told an air carrier flight to turn left immediately. The controller then asked if we were cleared to 11000 ft. We answered in the affirmative. We then picked up the air carrier set on our TCASII approaching from the rear at about 7 O'clock. We were at 15000 ft when the jet passed off our left side. We asked ATC to confirm that we were in fact cleared to 11000 ft. ATC did confirm that there was a controller mistake. Note: when we were given the urgent order to climb back to 15000 ft and heard the jet giving turn instruction, we of course suspected an altitude conflict. The first officer was flying the airplane, and I was searching the sky and the TCASII for traffic. I thought surely TCASII would show conflicting traffic, but because the TCASII has limited rearward looking capability, the jet aircraft was not seen until within 2 mi behind us. The jet's closure rate was fast enough to give little time for corrective action.

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Original NASA ASRS Text

Title: ACR HAS LTSS WITH MLG WHEN CLRED TO DSND THROUGH MLG ALT.

Narrative: FLT PROCEEDING ENRTE FROM HHH TO CLT. VIA DIRECT FLO WHEN ATC CLRED OUR FLT TO TURN L TO HDG OF 300 DEGS AND DSND OUT OF 15000 TO AN ALT OF 11000 FT. WHILE DSNDING THROUGH 14300 FT WE WERE GIVEN AN ORDER BY ATC TO CLB IMMEDIATELY TO 15000 FT. ATC THEN TOLD AN ACR FLT TO TURN L IMMEDIATELY. THE CTLR THEN ASKED IF WE WERE CLRED TO 11000 FT. WE ANSWERED IN THE AFFIRMATIVE. WE THEN PICKED UP THE ACR SET ON OUR TCASII APCHING FROM THE REAR AT ABOUT 7 O'CLOCK. WE WERE AT 15000 FT WHEN THE JET PASSED OFF OUR L SIDE. WE ASKED ATC TO CONFIRM THAT WE WERE IN FACT CLRED TO 11000 FT. ATC DID CONFIRM THAT THERE WAS A CTLR MISTAKE. NOTE: WHEN WE WERE GIVEN THE URGENT ORDER TO CLB BACK TO 15000 FT AND HEARD THE JET GIVING TURN INSTRUCTION, WE OF COURSE SUSPECTED AN ALT CONFLICT. THE FO WAS FLYING THE AIRPLANE, AND I WAS SEARCHING THE SKY AND THE TCASII FOR TFC. I THOUGHT SURELY TCASII WOULD SHOW CONFLICTING TFC, BUT BECAUSE THE TCASII HAS LIMITED REARWARD LOOKING CAPABILITY, THE JET ACFT WAS NOT SEEN UNTIL WITHIN 2 MI BEHIND US. THE JET'S CLOSURE RATE WAS FAST ENOUGH TO GIVE LITTLE TIME FOR CORRECTIVE ACTION.

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.