Narrative:

On climb out from rio we were assigned porto 3 departure. During climb out we were given 'fly heading 000 degrees and maintain FL110' by ATC. We were then cleared direct to asga waypoint. A short time later we were again instructed to 'fly heading 000 degrees and leaving FL250 cleared direct to asga.' as we passed FL250 on the climb to FL280 we initiated a turn (left) to asga. We advised ATC of our action at which time we were told to maintain heading (000 degrees in brazilian terminology, 360 degrees in USA terminology) and climb to FL280. ATC then advised us '...level at FL260' as we were passing FL265. We initiated an immediate descent to FL260 and advised ATC of our action. At this point a target appeared on TCASII at 12 O'clock position at around 15 NM at our level, opposite direction. ATC queried why we were at FL260 and instructed us to climb. We initiated an immediate 2000 FPM climb and 30 degree turn to right to avoid a traffic conflict and advised ATC of our actions. The TCASII target passed 10 NM left of us at FL260 (2000 ft below). We were subsequently cleared on course. ATC queried why we had descended to FL260. Our response was that he had cleared us to FL260 which he vehemently denied. Both pilots had heard this instruction. On reflection later we concluded that the instruction to maintain FL260 could possibly have been an air TA with the first part of the transmission garbled. Brazilian ATC have the habit of adding your call sign before and after a message. In any event we came no closer to the traffic than 10 NM and 2000 ft vertical separation.

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Original NASA ASRS Text

Title: FLC OF A DC10 MISUNDERSTOOD ATC AND DSNDED TO LAST ASSIGNED ALT DURING A DEP CLB RESULTING IN A TCASII ALERT OF OPPOSITE DIRECTION TFC AT THEIR SAME ALT. ATC INTERVENED AND INSTRUCTED THEM TO IMMEDIATELY CLB AS INSTRUCTED IN A PREVIOUS CLRNC PRIOR TO A TA WHICH THEY HAD MISUNDERSTOOD TO DSND.

Narrative: ON CLBOUT FROM RIO WE WERE ASSIGNED PORTO 3 DEP. DURING CLBOUT WE WERE GIVEN 'FLY HDG 000 DEGS AND MAINTAIN FL110' BY ATC. WE WERE THEN CLRED DIRECT TO ASGA WAYPOINT. A SHORT TIME LATER WE WERE AGAIN INSTRUCTED TO 'FLY HDG 000 DEGS AND LEAVING FL250 CLRED DIRECT TO ASGA.' AS WE PASSED FL250 ON THE CLB TO FL280 WE INITIATED A TURN (L) TO ASGA. WE ADVISED ATC OF OUR ACTION AT WHICH TIME WE WERE TOLD TO MAINTAIN HDG (000 DEGS IN BRAZILIAN TERMINOLOGY, 360 DEGS IN USA TERMINOLOGY) AND CLB TO FL280. ATC THEN ADVISED US '...LEVEL AT FL260' AS WE WERE PASSING FL265. WE INITIATED AN IMMEDIATE DSCNT TO FL260 AND ADVISED ATC OF OUR ACTION. AT THIS POINT A TARGET APPEARED ON TCASII AT 12 O'CLOCK POS AT AROUND 15 NM AT OUR LEVEL, OPPOSITE DIRECTION. ATC QUERIED WHY WE WERE AT FL260 AND INSTRUCTED US TO CLB. WE INITIATED AN IMMEDIATE 2000 FPM CLB AND 30 DEG TURN TO R TO AVOID A TFC CONFLICT AND ADVISED ATC OF OUR ACTIONS. THE TCASII TARGET PASSED 10 NM L OF US AT FL260 (2000 FT BELOW). WE WERE SUBSEQUENTLY CLRED ON COURSE. ATC QUERIED WHY WE HAD DSNDED TO FL260. OUR RESPONSE WAS THAT HE HAD CLRED US TO FL260 WHICH HE VEHEMENTLY DENIED. BOTH PLTS HAD HEARD THIS INSTRUCTION. ON REFLECTION LATER WE CONCLUDED THAT THE INSTRUCTION TO MAINTAIN FL260 COULD POSSIBLY HAVE BEEN AN AIR TA WITH THE FIRST PART OF THE XMISSION GARBLED. BRAZILIAN ATC HAVE THE HABIT OF ADDING YOUR CALL SIGN BEFORE AND AFTER A MESSAGE. IN ANY EVENT WE CAME NO CLOSER TO THE TFC THAN 10 NM AND 2000 FT VERT SEPARATION.

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.