Narrative:

While inbound to tlh at about 70 or 80 mi out at FL280 ATC cleared us to descend to FL230 then pilot's discretion to 10000'. I then programmed the computer accordingly and started a slow descent to FL230. Shortly afterwards a new controller began controling traffic and he reiterated our clearance to FL230. Rather than telling him that the previous controller had already cleared us to FL230, I simply acknowledged the transmission. Just prior to leveling at FL230 the VNAV mode activated and began a descent to 10000'. As we descended through FL230 (or maybe a little lower I guess about 22500') I looked out at 11 O'clock low and saw an fgt in a right turn. The controller advised us that the fgt pilot saw our aircraft. I did not have to take evasive action. The controller then told me that I was not cleared below FL230. I then told him that our clearance to FL230 contained a 'pd' to 10000'. He advised me that the pd portion of the clearance had been invalidated. West/O further comment on the matter we were again cleared to 10000'. If a portion of our clearance had been invalidated it was totally unclr to either member of this flight crew. A terrible lack of communication between the controller and this crew and also (I believe) between controllers changing work stations.

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Original NASA ASRS Text

Title: ACR DESCENDED BELOW ALT AND CONFLICTED WITH A FGT.

Narrative: WHILE INBND TO TLH AT ABOUT 70 OR 80 MI OUT AT FL280 ATC CLRED US TO DSND TO FL230 THEN PLT'S DISCRETION TO 10000'. I THEN PROGRAMMED THE COMPUTER ACCORDINGLY AND STARTED A SLOW DSCNT TO FL230. SHORTLY AFTERWARDS A NEW CTLR BEGAN CTLING TFC AND HE REITERATED OUR CLRNC TO FL230. RATHER THAN TELLING HIM THAT THE PREVIOUS CTLR HAD ALREADY CLRED US TO FL230, I SIMPLY ACKNOWLEDGED THE XMISSION. JUST PRIOR TO LEVELING AT FL230 THE VNAV MODE ACTIVATED AND BEGAN A DSCNT TO 10000'. AS WE DSNDED THROUGH FL230 (OR MAYBE A LITTLE LOWER I GUESS ABOUT 22500') I LOOKED OUT AT 11 O'CLOCK LOW AND SAW AN FGT IN A R TURN. THE CTLR ADVISED US THAT THE FGT PLT SAW OUR ACFT. I DID NOT HAVE TO TAKE EVASIVE ACTION. THE CTLR THEN TOLD ME THAT I WAS NOT CLRED BELOW FL230. I THEN TOLD HIM THAT OUR CLRNC TO FL230 CONTAINED A 'PD' TO 10000'. HE ADVISED ME THAT THE PD PORTION OF THE CLRNC HAD BEEN INVALIDATED. W/O FURTHER COMMENT ON THE MATTER WE WERE AGAIN CLRED TO 10000'. IF A PORTION OF OUR CLRNC HAD BEEN INVALIDATED IT WAS TOTALLY UNCLR TO EITHER MEMBER OF THIS FLT CREW. A TERRIBLE LACK OF COM BTWN THE CTLR AND THIS CREW AND ALSO (I BELIEVE) BTWN CTLRS CHANGING WORK STATIONS.

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.