Narrative:

During climb out, under control of ZLC and proceeding toward ocs on the slc 055 degree radial (J154), we received clearance initially to FL290. Before leveling at FL290, our clearance was changed by ATC to maintain FL330. When reading back the clearance to FL330, I stated that we were cleared to FL330, and (in the same readback) requested direct dbq. Center's reply was that he had our request. When the controller came back with our clearance, he apparently said, 'maintain FL290 and proceed direct ft dodge (FOD).' but I thought he said 'vacating FL290, proceed to FOD,' which is (essentially) what I read back, unaware of the new altitude assignment/restr. The controller made no correction to my readback. When we were passing FL300, he queried us as to why we didn't stop our climb at FL290, before proceeding direct to FOD. That was our first indication that there was a problem. (The TCASII showed no conflicts.) we immediately queried the controller as to whether or not he wanted us to descend back to FL290, to which he replied, no, continue climb to FL330. We were then instructed to call the center upon arrival in chicago. The captain spoke with the supervisor by phone after our arrival, who informed him that due to loss of required separation, the incident was initially being investigated as a pilot deviation, but that upon review of the tapes, it appeared to be a controller error.

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Original NASA ASRS Text

Title: A B727 WAS CLRED TO CLB TO FL330, THEN INSTRUCTED TO MAINTAIN FL290. THE FLC THOUGHT THE CTLR SAID TO 'VACATE' FL290 AND CONTINUED THEIR CLB TO AN OCCUPIED ALT. THE CTLR DID NOT CATCH THE PLT'S READBACK ERROR. THE PLT WAS ASKED TO CALL THE CTR UPON LNDG.

Narrative: DURING CLBOUT, UNDER CTL OF ZLC AND PROCEEDING TOWARD OCS ON THE SLC 055 DEG RADIAL (J154), WE RECEIVED CLRNC INITIALLY TO FL290. BEFORE LEVELING AT FL290, OUR CLRNC WAS CHANGED BY ATC TO MAINTAIN FL330. WHEN READING BACK THE CLRNC TO FL330, I STATED THAT WE WERE CLRED TO FL330, AND (IN THE SAME READBACK) REQUESTED DIRECT DBQ. CTR'S REPLY WAS THAT HE HAD OUR REQUEST. WHEN THE CTLR CAME BACK WITH OUR CLRNC, HE APPARENTLY SAID, 'MAINTAIN FL290 AND PROCEED DIRECT FT DODGE (FOD).' BUT I THOUGHT HE SAID 'VACATING FL290, PROCEED TO FOD,' WHICH IS (ESSENTIALLY) WHAT I READ BACK, UNAWARE OF THE NEW ALT ASSIGNMENT/RESTR. THE CTLR MADE NO CORRECTION TO MY READBACK. WHEN WE WERE PASSING FL300, HE QUERIED US AS TO WHY WE DIDN'T STOP OUR CLB AT FL290, BEFORE PROCEEDING DIRECT TO FOD. THAT WAS OUR FIRST INDICATION THAT THERE WAS A PROB. (THE TCASII SHOWED NO CONFLICTS.) WE IMMEDIATELY QUERIED THE CTLR AS TO WHETHER OR NOT HE WANTED US TO DSND BACK TO FL290, TO WHICH HE REPLIED, NO, CONTINUE CLB TO FL330. WE WERE THEN INSTRUCTED TO CALL THE CTR UPON ARR IN CHICAGO. THE CAPT SPOKE WITH THE SUPVR BY PHONE AFTER OUR ARR, WHO INFORMED HIM THAT DUE TO LOSS OF REQUIRED SEPARATION, THE INCIDENT WAS INITIALLY BEING INVESTIGATED AS A PLTDEV, BUT THAT UPON REVIEW OF THE TAPES, IT APPEARED TO BE A CTLR ERROR.

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.