Narrative:

During arrival to phx we had been cleared to 11000 ft. Due to high traffic volume approach control was slowing us down and giving us s-turn heading for spacing. From an eastbound heading we were assigned a 050 degree heading and descent to 9000 ft. A few seconds later the assigned heading became 010 degrees. From there we were clear to 170 degree heading, 7000 ft and slow to 170 KTS. We descended to 7000 ft while heading 170 degrees at 170 KTS. We were level at 7000 ft for about 2 mins and were assigned 010 degree heading and told that our assigned altitude was 9000 ft and instructed to climb. We were back at 9000 ft in 1 min. Other contributing factor was a flight with a call sign similar to ours. After receiving the clearance to 170 degrees, 170 KTS and 7000 ft, the system (still in autoflt) was set for speed and heading. I (PF) confirmed with the captain (PNF) that we were cleared to 7000 ft. He confirmed it and entered 7000 ft in the system. We both still believe we were issued a clearance to 7000 ft.

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Original NASA ASRS Text

Title: AN ACR MLG FLC DSNDS TO A LOWER ALT THAN THE APCH CTLR EXPECTED. THE CTLR HAD THEM CLB. NO CONFLICT.

Narrative: DURING ARR TO PHX WE HAD BEEN CLRED TO 11000 FT. DUE TO HIGH TFC VOLUME APCH CTL WAS SLOWING US DOWN AND GIVING US S-TURN HEADING FOR SPACING. FROM AN EBOUND HEADING WE WERE ASSIGNED A 050 DEG HDG AND DSCNT TO 9000 FT. A FEW SECONDS LATER THE ASSIGNED HDG BECAME 010 DEGS. FROM THERE WE WERE CLR TO 170 DEG HDG, 7000 FT AND SLOW TO 170 KTS. WE DSNDED TO 7000 FT WHILE HDG 170 DEGS AT 170 KTS. WE WERE LEVEL AT 7000 FT FOR ABOUT 2 MINS AND WERE ASSIGNED 010 DEG HDG AND TOLD THAT OUR ASSIGNED ALT WAS 9000 FT AND INSTRUCTED TO CLB. WE WERE BACK AT 9000 FT IN 1 MIN. OTHER CONTRIBUTING FACTOR WAS A FLT WITH A CALL SIGN SIMILAR TO OURS. AFTER RECEIVING THE CLRNC TO 170 DEGS, 170 KTS AND 7000 FT, THE SYS (STILL IN AUTOFLT) WAS SET FOR SPD AND HEADING. I (PF) CONFIRMED WITH THE CAPT (PNF) THAT WE WERE CLRED TO 7000 FT. HE CONFIRMED IT AND ENTERED 7000 FT IN THE SYS. WE BOTH STILL BELIEVE WE WERE ISSUED A CLRNC TO 7000 FT.

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.