Narrative:

Cruising at FL270 about 30 NM northwest spa, I went to #2 radio to contact operations regarding boy who threw up in cabin. Heard ATC (ZTL) clear us to descend to FL240, PF acknowledged, I came on hot microphone to confirm the new altitude set in the alerter, and PF initiated descent, selecting vertical speed 1500 FPM. I went back to conversation with dispatcher and some seconds later, overheard ATC ask meekly, if we could stay at FL270. PF asked ATC to repeat, I told dispatch to stand by, came on hot microphone and said 'he wants us to stay at FL270.' then checking TCASII and seeing FL260 traffic at 10 O'clock position and approximately 8 mi converging, I spun the vertical speed wheel up to stop descent-start climbing while ATC repeated his question. First officer replied yes, we can climb back to FL270. ATC queried us again, and first officer said that we were climbing back up to FL270 at this time. I spotted TCASII traffic visually and reported that to ATC. Lowest altitude reached was approximately FL267. As the FL260 traffic came inside 5-MI range on TCASII, we were climbing back through FL268. We were leveling at FL270 as the TCASII traffic passed about 2 mi behind and to the left. During the encounter, we got a TA on the traffic, no RA, and never saw the TCASII traffic change altitude on TCASII. A few mins later, controller said 'ok, let's try this again: 'air carrier X, descend and maintain FL240.' flight continued without further incident. I'm very thankful the controller caught his error before we had descended any further. There simply was no avoiding a loss of separation after receiving the descent clearance, given the time that elapsed until the controller called us back. I'm also glad that I'm in the habit of trying to monitor ATC at all times, even when using the other radio getting ATIS, calling dispatch, company operations, etc.

Google
 

Original NASA ASRS Text

Title: ZTL CTR REVERSED DSCNT CLRNC TO A CARJ1 FROM FL270 TO FL240 BECAUSE OF OPPOSITE DIRECTION TFC AT FL260. SEPARATION WAS LOST.

Narrative: CRUISING AT FL270 ABOUT 30 NM NW SPA, I WENT TO #2 RADIO TO CONTACT OPS REGARDING BOY WHO THREW UP IN CABIN. HEARD ATC (ZTL) CLR US TO DSND TO FL240, PF ACKNOWLEDGED, I CAME ON HOT MIKE TO CONFIRM THE NEW ALT SET IN THE ALERTER, AND PF INITIATED DSCNT, SELECTING VERT SPD 1500 FPM. I WENT BACK TO CONVERSATION WITH DISPATCHER AND SOME SECONDS LATER, OVERHEARD ATC ASK MEEKLY, IF WE COULD STAY AT FL270. PF ASKED ATC TO REPEAT, I TOLD DISPATCH TO STAND BY, CAME ON HOT MIKE AND SAID 'HE WANTS US TO STAY AT FL270.' THEN CHKING TCASII AND SEEING FL260 TFC AT 10 O'CLOCK POS AND APPROX 8 MI CONVERGING, I SPUN THE VERT SPD WHEEL UP TO STOP DSCNT-START CLBING WHILE ATC REPEATED HIS QUESTION. FO REPLIED YES, WE CAN CLB BACK TO FL270. ATC QUERIED US AGAIN, AND FO SAID THAT WE WERE CLBING BACK UP TO FL270 AT THIS TIME. I SPOTTED TCASII TFC VISUALLY AND RPTED THAT TO ATC. LOWEST ALT REACHED WAS APPROX FL267. AS THE FL260 TFC CAME INSIDE 5-MI RANGE ON TCASII, WE WERE CLBING BACK THROUGH FL268. WE WERE LEVELING AT FL270 AS THE TCASII TFC PASSED ABOUT 2 MI BEHIND AND TO THE L. DURING THE ENCOUNTER, WE GOT A TA ON THE TFC, NO RA, AND NEVER SAW THE TCASII TFC CHANGE ALT ON TCASII. A FEW MINS LATER, CTLR SAID 'OK, LET'S TRY THIS AGAIN: 'ACR X, DSND AND MAINTAIN FL240.' FLT CONTINUED WITHOUT FURTHER INCIDENT. I'M VERY THANKFUL THE CTLR CAUGHT HIS ERROR BEFORE WE HAD DSNDED ANY FURTHER. THERE SIMPLY WAS NO AVOIDING A LOSS OF SEPARATION AFTER RECEIVING THE DSCNT CLRNC, GIVEN THE TIME THAT ELAPSED UNTIL THE CTLR CALLED US BACK. I'M ALSO GLAD THAT I'M IN THE HABIT OF TRYING TO MONITOR ATC AT ALL TIMES, EVEN WHEN USING THE OTHER RADIO GETTING ATIS, CALLING DISPATCH, COMPANY OPS, ETC.

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.