Narrative:

We were cleared for takeoff from iah with a left turn to heading 120 degrees. On departure frequency 119.7 we checked in climbing to 4000 ft. Controller acknowledged and added 'no speed limit, higher in a few mi.' after passing 3100 ft AGL, I accelerated to 300 KIAS and leveled off at 4000 ft. Shortly, we were told to maintain 5000 ft, still heading 120 degrees at 300 KIAS. Much confusion soon occurred when the controller issued a clearance for what sounded to me like air carrier AE00 (we were AD00) turn right heading 180 degrees maintain 15000 ft. First officer read back heading and altitude assignment for air carrier AD00. No reply from controller. I wasn't sure if the clearance was for us and asked the first officer to verify it. No reply from controller, so I started the turn but remained at 5000 ft. Just a few moments later the controller issued us an immediate left turn to 090 degrees and immediate climb to 15000 ft which we complied with. The controller then started a lecture on not making turns that aren't assigned giving us a turn back right to 180 degrees. I asked to verify the heading assignment as I wasn't sure the controller really knew what he wanted us to do. We were then told to contact the TRACON upon arrival at destination. While we have to accept some of the blame for this incident, I still feel it resulted from the controller not listening to acknowledgments of his clrncs. To my knowledge, no separation was lost between aircraft and/or airspace but it was a possibility. Supplemental information from acn 392560: if we responded to heading and altitude improperly, it was not corrected when I read back the clearance. Also it seemed the controller also clipped the front end of his xmissions. I feel this incident could have been prevented if: 1) normal departure speed should have been given, 2) normal voice speeds should have been used, 3) if my readback clearance was inaccurate it should have been immediately corrected, and 4) it sounded as though the controller was working more than one frequency -- which could have contributed to the confusion.

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Original NASA ASRS Text

Title: A B727, UNDER IAH TRACON CTL, MISUNDERSTANDS CLRNC AND FLIES DIFFERENT HEADING AND DELAYS CLB TO ALT.

Narrative: WE WERE CLRED FOR TKOF FROM IAH WITH A L TURN TO HDG 120 DEGS. ON DEP FREQ 119.7 WE CHKED IN CLBING TO 4000 FT. CTLR ACKNOWLEDGED AND ADDED 'NO SPD LIMIT, HIGHER IN A FEW MI.' AFTER PASSING 3100 FT AGL, I ACCELERATED TO 300 KIAS AND LEVELED OFF AT 4000 FT. SHORTLY, WE WERE TOLD TO MAINTAIN 5000 FT, STILL HDG 120 DEGS AT 300 KIAS. MUCH CONFUSION SOON OCCURRED WHEN THE CTLR ISSUED A CLRNC FOR WHAT SOUNDED TO ME LIKE ACR AE00 (WE WERE AD00) TURN R HDG 180 DEGS MAINTAIN 15000 FT. FO READ BACK HEADING AND ALT ASSIGNMENT FOR ACR AD00. NO REPLY FROM CTLR. I WASN'T SURE IF THE CLRNC WAS FOR US AND ASKED THE FO TO VERIFY IT. NO REPLY FROM CTLR, SO I STARTED THE TURN BUT REMAINED AT 5000 FT. JUST A FEW MOMENTS LATER THE CTLR ISSUED US AN IMMEDIATE L TURN TO 090 DEGS AND IMMEDIATE CLB TO 15000 FT WHICH WE COMPLIED WITH. THE CTLR THEN STARTED A LECTURE ON NOT MAKING TURNS THAT AREN'T ASSIGNED GIVING US A TURN BACK R TO 180 DEGS. I ASKED TO VERIFY THE HEADING ASSIGNMENT AS I WASN'T SURE THE CTLR REALLY KNEW WHAT HE WANTED US TO DO. WE WERE THEN TOLD TO CONTACT THE TRACON UPON ARR AT DEST. WHILE WE HAVE TO ACCEPT SOME OF THE BLAME FOR THIS INCIDENT, I STILL FEEL IT RESULTED FROM THE CTLR NOT LISTENING TO ACKNOWLEDGMENTS OF HIS CLRNCS. TO MY KNOWLEDGE, NO SEPARATION WAS LOST BTWN ACFT AND/OR AIRSPACE BUT IT WAS A POSSIBILITY. SUPPLEMENTAL INFO FROM ACN 392560: IF WE RESPONDED TO HEADING AND ALT IMPROPERLY, IT WAS NOT CORRECTED WHEN I READ BACK THE CLRNC. ALSO IT SEEMED THE CTLR ALSO CLIPPED THE FRONT END OF HIS XMISSIONS. I FEEL THIS INCIDENT COULD HAVE BEEN PREVENTED IF: 1) NORMAL DEP SPD SHOULD HAVE BEEN GIVEN, 2) NORMAL VOICE SPDS SHOULD HAVE BEEN USED, 3) IF MY READBACK CLRNC WAS INACCURATE IT SHOULD HAVE BEEN IMMEDIATELY CORRECTED, AND 4) IT SOUNDED AS THOUGH THE CTLR WAS WORKING MORE THAN ONE FREQ -- WHICH COULD HAVE CONTRIBUTED TO THE CONFUSION.

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.