Narrative:

Aircraft #1 and aircraft #2 on parallel northbound heading for sequencing over arrival fix to the east. Aircraft #1 at FL190 north and west of aircraft #2 at 17000 ft. Call signs are similar and pilots are aware of each other. Aircraft #2 issued right turn to east heading and descent to 14000 ft. Clearance taken by aircraft #1. Incorrect call sign missed in readback. Aircraft #1 turned towards and descended through aircraft #2, who never altered heading or altitude. The installation of data link to display the altitude set in aircraft autoplt on controller data block could eliminate this and most other readback/hearback errors. Supplemental information from acn 392664: at that time the lead flight attendant opened the door to ask question. While I was momentarily answering flight attendant, the first officer received an ATC clearance. When I turned my attention back to flying the first officer advised me we were cleared to 14000 ft and turn to 090 degrees and intercept the crl 246 degree, mizar arrival. While he was off ATC requested my altitude. I responded, 16900 ft. ATC advised us to climb to FL180 and turn to 360 degrees. The same time we observed traffic at 1 O'clock position, 3 mi and 200 ft above us. The first officer advised me that ATC's original clearance was partially blocked due to the very congested frequency. He heard air carrier xa. When he responded to ATC to descend to 14000 ft and turn he included our call sign air carrier XXXA. ATC responded, roger, resume normal speed. First officer, responded roger, normal speed air carrier XXXA. Supplemental information from acn 392451: I heard a partially covered call sign ending in xa. Our call sign was XXXA. The radio calls went something like this: ATC: air carrier ??xa turn right to 090 degrees descend and maintain 14000 ft, intercept the crl 246 degree radial inbound, expect mizar at 12 and 250. Me: I paused a few seconds then replied: understand right to 090 degrees, intercept the arrival, descend to 14000 ft, we're already at 250 KTS, air carrier XXXA. ATC: roger, resume normal airspeed, expect mizar at 12 and 250. Me: normal airspeed air carrier XXXA. ATC: expect mizar at 12 and 250. Me: roger. Factors: captain distracted with other duties (no backup for me). Radio congestion partially covering a call sign. Similar call signs, there was air carrier yyxa in the area. Me accepting the clearance without positively insisting that ATC confirm the call was for us. ATC was very busy and most likely did not catch my call sign during the readbacks.

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Original NASA ASRS Text

Title: RPTED LOSS OF SEPARATION WHEN FO OF ACR DC9 TAKES CLRNC FOR OTHER ACFT WITH SIMILAR CALL SIGN AND THE READBACK WITH CALL SIGN IS MISSED BY THE CTLR.

Narrative: ACFT #1 AND ACFT #2 ON PARALLEL NBOUND HEADING FOR SEQUENCING OVER ARR FIX TO THE E. ACFT #1 AT FL190 N AND W OF ACFT #2 AT 17000 FT. CALL SIGNS ARE SIMILAR AND PLTS ARE AWARE OF EACH OTHER. ACFT #2 ISSUED R TURN TO E HEADING AND DSCNT TO 14000 FT. CLRNC TAKEN BY ACFT #1. INCORRECT CALL SIGN MISSED IN READBACK. ACFT #1 TURNED TOWARDS AND DSNDED THROUGH ACFT #2, WHO NEVER ALTERED HEADING OR ALT. THE INSTALLATION OF DATA LINK TO DISPLAY THE ALT SET IN ACFT AUTOPLT ON CTLR DATA BLOCK COULD ELIMINATE THIS AND MOST OTHER READBACK/HEARBACK ERRORS. SUPPLEMENTAL INFO FROM ACN 392664: AT THAT TIME THE LEAD FLT ATTENDANT OPENED THE DOOR TO ASK QUESTION. WHILE I WAS MOMENTARILY ANSWERING FLT ATTENDANT, THE FO RECEIVED AN ATC CLRNC. WHEN I TURNED MY ATTN BACK TO FLYING THE FO ADVISED ME WE WERE CLRED TO 14000 FT AND TURN TO 090 DEGS AND INTERCEPT THE CRL 246 DEG, MIZAR ARR. WHILE HE WAS OFF ATC REQUESTED MY ALT. I RESPONDED, 16900 FT. ATC ADVISED US TO CLB TO FL180 AND TURN TO 360 DEGS. THE SAME TIME WE OBSERVED TFC AT 1 O'CLOCK POS, 3 MI AND 200 FT ABOVE US. THE FO ADVISED ME THAT ATC'S ORIGINAL CLRNC WAS PARTIALLY BLOCKED DUE TO THE VERY CONGESTED FREQ. HE HEARD ACR XA. WHEN HE RESPONDED TO ATC TO DSND TO 14000 FT AND TURN HE INCLUDED OUR CALL SIGN ACR XXXA. ATC RESPONDED, ROGER, RESUME NORMAL SPD. FO, RESPONDED ROGER, NORMAL SPD ACR XXXA. SUPPLEMENTAL INFO FROM ACN 392451: I HEARD A PARTIALLY COVERED CALL SIGN ENDING IN XA. OUR CALL SIGN WAS XXXA. THE RADIO CALLS WENT SOMETHING LIKE THIS: ATC: ACR ??XA TURN R TO 090 DEGS DSND AND MAINTAIN 14000 FT, INTERCEPT THE CRL 246 DEG RADIAL INBOUND, EXPECT MIZAR AT 12 AND 250. ME: I PAUSED A FEW SECONDS THEN REPLIED: UNDERSTAND R TO 090 DEGS, INTERCEPT THE ARR, DSND TO 14000 FT, WE'RE ALREADY AT 250 KTS, ACR XXXA. ATC: ROGER, RESUME NORMAL AIRSPD, EXPECT MIZAR AT 12 AND 250. ME: NORMAL AIRSPD ACR XXXA. ATC: EXPECT MIZAR AT 12 AND 250. ME: ROGER. FACTORS: CAPT DISTRACTED WITH OTHER DUTIES (NO BACKUP FOR ME). RADIO CONGESTION PARTIALLY COVERING A CALL SIGN. SIMILAR CALL SIGNS, THERE WAS ACR YYXA IN THE AREA. ME ACCEPTING THE CLRNC WITHOUT POSITIVELY INSISTING THAT ATC CONFIRM THE CALL WAS FOR US. ATC WAS VERY BUSY AND MOST LIKELY DID NOT CATCH MY CALL SIGN DURING THE READBACKS.

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.