Narrative:

Captain was flying, I was talking. We were 30 mi east of mci at 12000 ft, talking to mci approach. We were cleared to descend to 4000 ft. I acknowledged, and the captain and I did the SOP, then he initiated the descent. We became aware of another aircraft on the frequency when approach used our call sign while responding to them. The captain asked me to verify our clearance, and after 2 attempts approach told us we were not cleared to descend, the call was for someone else, and that we were now cleared to 10000 ft. In the meantime, the captain had leveled us at 10700 ft. Human factors: 1) the captain made an excellent call in asking me to verify the clearance, as I was 100% sure of it. 2) the approach controller did not inform us of another aircraft on frequency with a similar sounding call sign. 3) the controller did not correct me when I repeated our descent clearance in error. 4) the controller 'clipped' the call sign portion (prior to the numbers) of our call sign -- both before and after the event. 5) even after the event, it was very difficult to determine our call sign due to the controller's technique. 6) the initial descent clearance was believable due to our altitude and proximity to mci (30 mi and 12000 ft).

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Original NASA ASRS Text

Title: A320 ACR CREW AT 12000 FT DSNDING TO 4000 FT ARREST THEIR LETDOWN WHEN THE CTLR USED THE SAME CALL SIGN WITH ANOTHER ACFT.

Narrative: CAPT WAS FLYING, I WAS TALKING. WE WERE 30 MI E OF MCI AT 12000 FT, TALKING TO MCI APCH. WE WERE CLRED TO DSND TO 4000 FT. I ACKNOWLEDGED, AND THE CAPT AND I DID THE SOP, THEN HE INITIATED THE DSCNT. WE BECAME AWARE OF ANOTHER ACFT ON THE FREQ WHEN APCH USED OUR CALL SIGN WHILE RESPONDING TO THEM. THE CAPT ASKED ME TO VERIFY OUR CLRNC, AND AFTER 2 ATTEMPTS APCH TOLD US WE WERE NOT CLRED TO DSND, THE CALL WAS FOR SOMEONE ELSE, AND THAT WE WERE NOW CLRED TO 10000 FT. IN THE MEANTIME, THE CAPT HAD LEVELED US AT 10700 FT. HUMAN FACTORS: 1) THE CAPT MADE AN EXCELLENT CALL IN ASKING ME TO VERIFY THE CLRNC, AS I WAS 100% SURE OF IT. 2) THE APCH CTLR DID NOT INFORM US OF ANOTHER ACFT ON FREQ WITH A SIMILAR SOUNDING CALL SIGN. 3) THE CTLR DID NOT CORRECT ME WHEN I REPEATED OUR DSCNT CLRNC IN ERROR. 4) THE CTLR 'CLIPPED' THE CALL SIGN PORTION (PRIOR TO THE NUMBERS) OF OUR CALL SIGN -- BOTH BEFORE AND AFTER THE EVENT. 5) EVEN AFTER THE EVENT, IT WAS VERY DIFFICULT TO DETERMINE OUR CALL SIGN DUE TO THE CTLR'S TECHNIQUE. 6) THE INITIAL DSCNT CLRNC WAS BELIEVABLE DUE TO OUR ALT AND PROX TO MCI (30 MI AND 12000 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.