Narrative:

Flight abc at 35000', cruise. Flight received what we believed to be a clearance to descend to 240 from ZMA. Commenced our descent and at approximately FL340 ZMA issued a clearance to level off at FL330 and questioned why we were descending. After explaining that we had acknowledged the clearance to FL240. He said we had taken a clearance for company flight agc and at that time the captain for agc came on the air and told ZMA that he had not received or acknowledged any clearance. There was no reply from ZMA. A short time passed and ZMA called company agc and cleared them to FL240. We then returned calls to ZMA and requested the controller's name, phone # contact and asked if there was any conflict with other aircraft or loss of sep. He stated there was none. I then questioned several pilots on the ground in mia who were inbound and on the same frequency and they indicated they had heard the same thing we did. I then notified company legal department, safety department, vp of flight operations and requested a copy of ZMA's tapes. The following day I discussed the incident with area supervisor ZMA. He told me the same information as above (no loss of sep), but said we had mistakenly accepted, acknowledged and computed with the clearance for company agc and his controller had not caught it and corrected us. Herein lies the problem: 80-90% of the time, especially in high density, extremely busy sectors, clrncs are received, acknowledged and not confirmed by ATC. Example: (ATC)-air carrier lmn climb and maintain 15 thousand.' (air carrier lmn)-leaving 10 thousand for 15 thousand.' --silence-- did ATC hear him? Was the clearance correct? Both ATC and the air carrier are guilty of this. We must start emphasizing the importance of that final confirmation for the pilot and the controller.

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Original NASA ASRS Text

Title: ACR MLG CLRNC RESPONSE TO WRONG CALL SIGN OR ARTCC RADAR TLR USED THE WRONG CALL SIGN RESULTING IN DESCENT FROM CLRNC ALT.

Narrative: FLT ABC AT 35000', CRUISE. FLT RECEIVED WHAT WE BELIEVED TO BE A CLRNC TO DSND TO 240 FROM ZMA. COMMENCED OUR DSCNT AND AT APPROX FL340 ZMA ISSUED A CLRNC TO LEVEL OFF AT FL330 AND QUESTIONED WHY WE WERE DSNDING. AFTER EXPLAINING THAT WE HAD ACKNOWLEDGED THE CLRNC TO FL240. HE SAID WE HAD TAKEN A CLRNC FOR COMPANY FLT AGC AND AT THAT TIME THE CAPT FOR AGC CAME ON THE AIR AND TOLD ZMA THAT HE HAD NOT RECEIVED OR ACKNOWLEDGED ANY CLRNC. THERE WAS NO REPLY FROM ZMA. A SHORT TIME PASSED AND ZMA CALLED COMPANY AGC AND CLRED THEM TO FL240. WE THEN RETURNED CALLS TO ZMA AND REQUESTED THE CTLR'S NAME, PHONE # CONTACT AND ASKED IF THERE WAS ANY CONFLICT WITH OTHER ACFT OR LOSS OF SEP. HE STATED THERE WAS NONE. I THEN QUESTIONED SEVERAL PLTS ON THE GND IN MIA WHO WERE INBND AND ON THE SAME FREQ AND THEY INDICATED THEY HAD HEARD THE SAME THING WE DID. I THEN NOTIFIED COMPANY LEGAL DEPT, SAFETY DEPT, VP OF FLT OPS AND REQUESTED A COPY OF ZMA'S TAPES. THE FOLLOWING DAY I DISCUSSED THE INCIDENT WITH AREA SUPVR ZMA. HE TOLD ME THE SAME INFO AS ABOVE (NO LOSS OF SEP), BUT SAID WE HAD MISTAKENLY ACCEPTED, ACKNOWLEDGED AND COMPUTED WITH THE CLRNC FOR COMPANY AGC AND HIS CTLR HAD NOT CAUGHT IT AND CORRECTED US. HEREIN LIES THE PROB: 80-90% OF THE TIME, ESPECIALLY IN HIGH DENSITY, EXTREMELY BUSY SECTORS, CLRNCS ARE RECEIVED, ACKNOWLEDGED AND NOT CONFIRMED BY ATC. EXAMPLE: (ATC)-ACR LMN CLB AND MAINTAIN 15 THOUSAND.' (ACR LMN)-LEAVING 10 THOUSAND FOR 15 THOUSAND.' --SILENCE-- DID ATC HEAR HIM? WAS THE CLRNC CORRECT? BOTH ATC AND THE ACR ARE GUILTY OF THIS. WE MUST START EMPHASIZING THE IMPORTANCE OF THAT FINAL CONFIRMATION FOR THE PLT AND THE CTLR.

Data retrieved from NASA's ASRS site as of August 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.