Narrative:

We were on low altitude center frequency out of mia I climbing to assigned altitude of 16000 ft with an assigned heading of 230 degrees. We were queried by center about our final altitude. The choice was FL280 or FL350. We requested FL280. Center cleared us to FL280. We then were given a frequency change to 132.2 high sector. When I checked in with center I stated 'air carrier flight number leaving FL200(?) for FL280 heading 230 degrees assigned.' ATC response was 'roger.' as we were climbing through FL220 center assigned us a heading of 180 degrees. We then noticed an aircraft on TCASII at FL240. At that moment we were asked by center what our altitude was. I responded 'FL237.' center then said 'you were assigned FL230.' I responded that our assigned flight level was FL280. Center gave us a further turn to 150 degrees and did not mention our altitude again. All cockpit crew members agreed without doubt that our assigned altitude was FL280. The horizontal separation from the aircraft at FL240 was about 7 NM at its closest point. I believe that on the initial call, the high altitude center controller did not hear the 'FL280' and heard only '230 degree heading assigned' and mistook 230 degrees for FL230. This probably explains the miscom. Next time I will not include a heading on the initial call to the next controller.

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Original NASA ASRS Text

Title: FLC OF ACR LGT ACFT OVERSHOT CLB ALT ASSIGNMENT RESULTING IN LTSS.

Narrative: WE WERE ON LOW ALT CTR FREQ OUT OF MIA I CLBING TO ASSIGNED ALT OF 16000 FT WITH AN ASSIGNED HDG OF 230 DEGS. WE WERE QUERIED BY CTR ABOUT OUR FINAL ALT. THE CHOICE WAS FL280 OR FL350. WE REQUESTED FL280. CTR CLRED US TO FL280. WE THEN WERE GIVEN A FREQ CHANGE TO 132.2 HIGH SECTOR. WHEN I CHKED IN WITH CTR I STATED 'ACR FLT NUMBER LEAVING FL200(?) FOR FL280 HDG 230 DEGS ASSIGNED.' ATC RESPONSE WAS 'ROGER.' AS WE WERE CLBING THROUGH FL220 CTR ASSIGNED US A HDG OF 180 DEGS. WE THEN NOTICED AN ACFT ON TCASII AT FL240. AT THAT MOMENT WE WERE ASKED BY CTR WHAT OUR ALT WAS. I RESPONDED 'FL237.' CTR THEN SAID 'YOU WERE ASSIGNED FL230.' I RESPONDED THAT OUR ASSIGNED FLT LEVEL WAS FL280. CTR GAVE US A FURTHER TURN TO 150 DEGS AND DID NOT MENTION OUR ALT AGAIN. ALL COCKPIT CREW MEMBERS AGREED WITHOUT DOUBT THAT OUR ASSIGNED ALT WAS FL280. THE HORIZ SEPARATION FROM THE ACFT AT FL240 WAS ABOUT 7 NM AT ITS CLOSEST POINT. I BELIEVE THAT ON THE INITIAL CALL, THE HIGH ALT CTR CTLR DID NOT HEAR THE 'FL280' AND HEARD ONLY '230 DEG HDG ASSIGNED' AND MISTOOK 230 DEGS FOR FL230. THIS PROBABLY EXPLAINS THE MISCOM. NEXT TIME I WILL NOT INCLUDE A HDG ON THE INITIAL CALL TO THE NEXT CTLR.

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.