Narrative:

Enroute to zggg there was a line of very active thunderstorms between ZZZZ and zggg (east to west moving at about 50 KTS at altitude). To get into zggg airspace we had to deviate 100 NM east of ZZZZ and snake our way around many storms. We expected an approach to runway 20L. As we neared the zggg airport; ATC informed us that runway 02R was now in use and then we had to work our way around more storms to make progress on radar downwind for the approach on about heading 200 degrees. As we passed abeam the approach end of runway 02R; I informed ATC that we would need a shorter turn to final approach due to a big storm on final at about 12 NM. They acknowledged their understanding. We were cleared descent to 1;800 meters and to slow to 180 KTS; slats came out followed by flaps 15 and the descent rate was reduced to make the deceleration. We were in a slow and easy descent and expected a turn to base leg in about 5-6 miles. Then ATC made a frantic; very excited transmission for an aircraft to descend to or maintain 1;800 meters and turn right to a heading of about 300 degrees (the transmission wasn't very clear and the voice was very frantic and abrupt so the exact heading may be different). I did not hear a call sign with the transmission. ATC repeated the frantic message now instructing the aircraft to climb to 2;100 meters and make the right turn and I thought I heard part of a call sign. I keyed the mike and asked for the call sign to be repeated; 'repeat call sign; call sign.' ATC said it was for us! At the same time the TCAS sounded with a 'traffic; traffic' alert and I looked down to see a yellow triangle symbol ahead and about 45 degrees to the left at 600 ft below our altitude. I don't know the distance as the airbus TCAS is not so easy to read (I had confidence and experience using a TCAS display on the nd); especially in the adverse conditions (it was dark and stormy; we were reacting to a frantic call from ATC to some aircraft that turned out to be us; changing instructions with a requirement to convert all altitude instructions from meters to feet using a decoder card and english as a second language for the controllers). It may have been 3-4 miles. We still had 12 NM range selected and I didn't notice any aircraft displayed until then. I announced what I saw on the TCAS at about the same time as the captain disconnected the autopilot and followed ATC's instructions. There was no RA alert. I believe that ATC then instructed [the other aircraft] to maintain 1;800 meters and make a conflict deviation turn; followed by a descent to 900 meters and then make progress to final approach. It appeared that aircraft was on radar base leg flying left to right ahead of us while we were on downwind. Once we followed ATC's instructions the conflict was over; things settled down very quickly and we continued and flew the ILS to runway 02R. I thought ATC had done a fairly good job letting all the arrival aircraft make their own storm deviations with so many storms in the area but at the time of the conflict I think ATC confused the two aircraft on their displays when one was on downwind and the other on base leg and in very close proximity with a storm limiting the maneuvering airspace for the approach. I think he gave us a descent to 1;800 meters when he intended it for the other airplane. Then we descended into their flight path. I don't recall any other call sign confusion until that point and never felt confused myself by the different call signs in the pattern. Company use of call signs that are so similar to each other in the same location and same time are very confusing for both the controllers and the pilots. Do not use very similar call signs in the same location and time.

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Original NASA ASRS Text

Title: Air Carrier flight crew describes an airborne conflict that develops when a Controller confuses similar call signs (one digit difference) descending a second aircraft to an occupied altitude. The error is detected and corrected by the Controller in a timely manor.

Narrative: Enroute to ZGGG there was a line of very active thunderstorms between ZZZZ and ZGGG (east to west moving at about 50 KTS at altitude). To get into ZGGG airspace we had to deviate 100 NM east of ZZZZ and snake our way around many storms. We expected an approach to Runway 20L. As we neared the ZGGG airport; ATC informed us that Runway 02R was now in use and then we had to work our way around more storms to make progress on radar downwind for the approach on about heading 200 degrees. As we passed abeam the approach end of Runway 02R; I informed ATC that we would need a shorter turn to final approach due to a big storm on final at about 12 NM. They acknowledged their understanding. We were cleared descent to 1;800 meters and to slow to 180 KTS; slats came out followed by flaps 15 and the descent rate was reduced to make the deceleration. We were in a slow and easy descent and expected a turn to base leg in about 5-6 miles. Then ATC made a frantic; very excited transmission for an aircraft to descend to or maintain 1;800 meters and turn right to a heading of about 300 degrees (the transmission wasn't very clear and the voice was very frantic and abrupt so the exact heading may be different). I did not hear a call sign with the transmission. ATC repeated the frantic message now instructing the aircraft to climb to 2;100 meters and make the right turn and I thought I heard part of a call sign. I keyed the mike and asked for the call sign to be repeated; 'Repeat call sign; call sign.' ATC said it was for us! At the same time the TCAS sounded with a 'Traffic; Traffic' alert and I looked down to see a yellow triangle symbol ahead and about 45 degrees to the left at 600 FT below our altitude. I don't know the distance as the Airbus TCAS is not so easy to read (I had confidence and experience using a TCAS display on the ND); especially in the adverse conditions (it was dark and stormy; we were reacting to a frantic call from ATC to some aircraft that turned out to be us; changing instructions with a requirement to convert all altitude instructions from meters to feet using a decoder card and English as a second language for the controllers). It may have been 3-4 miles. We still had 12 NM range selected and I didn't notice any aircraft displayed until then. I announced what I saw on the TCAS at about the same time as the Captain disconnected the autopilot and followed ATC's instructions. There was no RA alert. I believe that ATC then instructed [the other aircraft] to maintain 1;800 meters and make a conflict deviation turn; followed by a descent to 900 meters and then make progress to final approach. It appeared that aircraft was on radar base leg flying left to right ahead of us while we were on downwind. Once we followed ATC's instructions the conflict was over; things settled down very quickly and we continued and flew the ILS to Runway 02R. I thought ATC had done a fairly good job letting all the arrival aircraft make their own storm deviations with so many storms in the area but at the time of the conflict I think ATC confused the two aircraft on their displays when one was on downwind and the other on base leg and in very close proximity with a storm limiting the maneuvering airspace for the approach. I think he gave us a descent to 1;800 meters when he intended it for the other airplane. Then we descended into their flight path. I don't recall any other call sign confusion until that point and never felt confused myself by the different call signs in the pattern. Company use of call signs that are so similar to each other in the same location and same time are very confusing for both the controllers and the pilots. Do not use very similar call signs in the same location and time.

Data retrieved from NASA's ASRS site 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.