Narrative:

We had been cleared the cedar creek 2 arrival. While on regional approach control, approximately 3-4 NM north of tacke, we were cleared to descend from 11000 ft to 7000 ft and switch to another regional approach frequency. I read back the clearance to 7000 ft, the new approach frequency and our call sign. After checking in with the new controller, he acknowledged our check-in with air carrier xa. I responded with air carrier axxa and our altitude clearance. His response was air carrier xa, what's your position. I didn't respond to the other call sign so as not to confuse the situation and clutter the radio traffic. I was waiting for air carrier xa to respond, and then I would check-in again. However, after a few seconds, the controller said, air carrier axxa, climb immediately to 11000 ft, and switch back to your previous frequency. The first officer (PF) had descended to 10300 ft and there was TCASII traffic on the nose about 8 NM, approximately 200 ft below our altitude, and descending. After switching back to our original frequency, I inquired about the confusion. The controller said it was no problem. Apparently, the TCASII traffic on our nose was air carrier xa. Supplemental information from acn 405580: the controller told not to worry and that this confusion was due to similar sounding call signs. Our lowest altitude was 10300 ft and we did observe traffic on the TCASII 8 mi on our nose 100 ft below us.

Google
 

Original NASA ASRS Text

Title: AN ACR PIC RESPONDS TO A WRONG CALL SIGN AND THE FO, PF, PERFORMS AN ALT EXCURSION.

Narrative: WE HAD BEEN CLRED THE CEDAR CREEK 2 ARR. WHILE ON REGIONAL APCH CTL, APPROX 3-4 NM N OF TACKE, WE WERE CLRED TO DSND FROM 11000 FT TO 7000 FT AND SWITCH TO ANOTHER REGIONAL APCH FREQ. I READ BACK THE CLRNC TO 7000 FT, THE NEW APCH FREQ AND OUR CALL SIGN. AFTER CHKING IN WITH THE NEW CTLR, HE ACKNOWLEDGED OUR CHK-IN WITH ACR XA. I RESPONDED WITH ACR AXXA AND OUR ALT CLRNC. HIS RESPONSE WAS ACR XA, WHAT'S YOUR POS. I DIDN'T RESPOND TO THE OTHER CALL SIGN SO AS NOT TO CONFUSE THE SIT AND CLUTTER THE RADIO TFC. I WAS WAITING FOR ACR XA TO RESPOND, AND THEN I WOULD CHK-IN AGAIN. HOWEVER, AFTER A FEW SECONDS, THE CTLR SAID, ACR AXXA, CLB IMMEDIATELY TO 11000 FT, AND SWITCH BACK TO YOUR PREVIOUS FREQ. THE FO (PF) HAD DSNDED TO 10300 FT AND THERE WAS TCASII TFC ON THE NOSE ABOUT 8 NM, APPROX 200 FT BELOW OUR ALT, AND DSNDING. AFTER SWITCHING BACK TO OUR ORIGINAL FREQ, I INQUIRED ABOUT THE CONFUSION. THE CTLR SAID IT WAS NO PROB. APPARENTLY, THE TCASII TFC ON OUR NOSE WAS ACR XA. SUPPLEMENTAL INFO FROM ACN 405580: THE CTLR TOLD NOT TO WORRY AND THAT THIS CONFUSION WAS DUE TO SIMILAR SOUNDING CALL SIGNS. OUR LOWEST ALT WAS 10300 FT AND WE DID OBSERVE TFC ON THE TCASII 8 MI ON OUR NOSE 100 FT BELOW US.

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.