Narrative:

This report addresses an ATC/pilot communications breakdown, which resulted in the controller giving us immediate climb and turn directives to avoid a traffic conflict. We were a few mi south and west of slc airport north/nwbound expecting a visual approach for runway 16R. We were at 11000 ft. ATC communication seemed to be quite busy at times. The captain was flying, first officer doing communication. We (believed that we) were given a clearance to descend to 8500 ft and also a statement about speed reduction. First officer read back the instruction to descend to 8500 ft along with our flight number as well as queried the controller about the speed reduction. At this point, there was a garbled transmission, which was unreadable to us. Perhaps at this point, there should have been some additional inquiries on our part or the part of the controller. Perhaps less than a min later, ATC instructed us to make an immediate climb to 11000 ft, and soon thereafter, an immediate right turn to a specified heading (I believe it was 010). We did not experience a 'TA' on TCASII. After the flight, the controller and I each explained our experience with the matter. Ultimately, the tapes were referenced. Although I did not hear the tape, the controller, in essence, stated that the tape records that the instruction to descend, was given to another flight number, not ours. He then said that our readback was garbled, because there was another transmission from another aircraft at the same time and that neither transmission was recognizable nor discernible. He mentioned that he also had to give our conflicting traffic an immediate descent. In afterthought, if the controller is correct in that the tape, indeed, records that we responded to an incorrect flight number, then it is evident that the pilots should have caught this. Both pilots were fatigued, as it was a very early start that day (about XA30). The captain was in doubt a little later as to the clearance and was about to ask. It was at this point that the immediate action was directed by ATC. It was a busy communications time, with people occasionally 'stepping on each other' in their xmissions. It would have been good for the controller to verify instructions given when replies back to him were garbled. I think factors of pilot alertness (this was an arrival that is flown very, very often), fatigue, congestion in the approach area, and busy communications all contributed to this incident.

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Original NASA ASRS Text

Title: SLC EMB120 ARR INITIATES DSCNT IN CONFLICT WITH ATC INSTRUCTIONS AND OTHER ACFT.

Narrative: THIS RPT ADDRESSES AN ATC/PLT COMS BREAKDOWN, WHICH RESULTED IN THE CTLR GIVING US IMMEDIATE CLB AND TURN DIRECTIVES TO AVOID A TFC CONFLICT. WE WERE A FEW MI S AND W OF SLC ARPT N/NWBOUND EXPECTING A VISUAL APCH FOR RWY 16R. WE WERE AT 11000 FT. ATC COM SEEMED TO BE QUITE BUSY AT TIMES. THE CAPT WAS FLYING, FO DOING COM. WE (BELIEVED THAT WE) WERE GIVEN A CLRNC TO DSND TO 8500 FT AND ALSO A STATEMENT ABOUT SPD REDUCTION. FO READ BACK THE INSTRUCTION TO DSND TO 8500 FT ALONG WITH OUR FLT NUMBER AS WELL AS QUERIED THE CTLR ABOUT THE SPD REDUCTION. AT THIS POINT, THERE WAS A GARBLED XMISSION, WHICH WAS UNREADABLE TO US. PERHAPS AT THIS POINT, THERE SHOULD HAVE BEEN SOME ADDITIONAL INQUIRIES ON OUR PART OR THE PART OF THE CTLR. PERHAPS LESS THAN A MIN LATER, ATC INSTRUCTED US TO MAKE AN IMMEDIATE CLB TO 11000 FT, AND SOON THEREAFTER, AN IMMEDIATE R TURN TO A SPECIFIED HDG (I BELIEVE IT WAS 010). WE DID NOT EXPERIENCE A 'TA' ON TCASII. AFTER THE FLT, THE CTLR AND I EACH EXPLAINED OUR EXPERIENCE WITH THE MATTER. ULTIMATELY, THE TAPES WERE REFED. ALTHOUGH I DID NOT HEAR THE TAPE, THE CTLR, IN ESSENCE, STATED THAT THE TAPE RECORDS THAT THE INSTRUCTION TO DSND, WAS GIVEN TO ANOTHER FLT NUMBER, NOT OURS. HE THEN SAID THAT OUR READBACK WAS GARBLED, BECAUSE THERE WAS ANOTHER XMISSION FROM ANOTHER ACFT AT THE SAME TIME AND THAT NEITHER XMISSION WAS RECOGNIZABLE NOR DISCERNIBLE. HE MENTIONED THAT HE ALSO HAD TO GIVE OUR CONFLICTING TFC AN IMMEDIATE DSCNT. IN AFTERTHOUGHT, IF THE CTLR IS CORRECT IN THAT THE TAPE, INDEED, RECORDS THAT WE RESPONDED TO AN INCORRECT FLT NUMBER, THEN IT IS EVIDENT THAT THE PLTS SHOULD HAVE CAUGHT THIS. BOTH PLTS WERE FATIGUED, AS IT WAS A VERY EARLY START THAT DAY (ABOUT XA30). THE CAPT WAS IN DOUBT A LITTLE LATER AS TO THE CLRNC AND WAS ABOUT TO ASK. IT WAS AT THIS POINT THAT THE IMMEDIATE ACTION WAS DIRECTED BY ATC. IT WAS A BUSY COMS TIME, WITH PEOPLE OCCASIONALLY 'STEPPING ON EACH OTHER' IN THEIR XMISSIONS. IT WOULD HAVE BEEN GOOD FOR THE CTLR TO VERIFY INSTRUCTIONS GIVEN WHEN REPLIES BACK TO HIM WERE GARBLED. I THINK FACTORS OF PLT ALERTNESS (THIS WAS AN ARR THAT IS FLOWN VERY, VERY OFTEN), FATIGUE, CONGESTION IN THE APCH AREA, AND BUSY COMS ALL CONTRIBUTED TO THIS INCIDENT.

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.