Narrative:

We were en route from day to lga. We had been on the milton 3 arrival into lga, in IMC conditions. We had changed frequencys and were told to descend to 9000 ft MSL, just after we had passed the benty intersection. The controller vectored us to a heading of 130 degrees for sequencing into lga. She called and told flight abcd, 'descend to 7000 ft MSL.' we had not been told of any similar flight numbers being on the frequency and called to confirm that it was 'flight aecd down to 7000 ft MSL,' but did not get a response and assumed it was due to her workload. We reached 7000 ft and were following her vectors. When she gave approach instructions to flight abcd, we still had not been informed that they were on the frequency. Before we could respond to correct the controller that our flight number was in fact aecd, flight abcd accepted the instructions to join the approach to runway 4 in lga. As soon as we realized the error, we contacted approach and notified them of our altitude and began to climb back to 9000 ft. Her only response was 'I know,' without any instruction on what altitude she wanted us to return to. As we were passing through about 7500 ft MSL, she instructed us to return to 7000 ft. Roughly 20-30 seconds (seemed a lot longer). We returned to 7000 ft MSL and were handed off to 2 more frequencys before any controller notified us that we were following chq flight #abcd into lga and to be aware of similar call signs. We continued the flight without incident.

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Original NASA ASRS Text

Title: EMB145 INBOUND FOR LGA DSNDS WITHOUT ATC CLRNC, SIMILAR CALL SIGNS.

Narrative: WE WERE ENRTE FROM DAY TO LGA. WE HAD BEEN ON THE MILTON 3 ARR INTO LGA, IN IMC CONDITIONS. WE HAD CHANGED FREQS AND WERE TOLD TO DSND TO 9000 FT MSL, JUST AFTER WE HAD PASSED THE BENTY INTXN. THE CTLR VECTORED US TO A HEADING OF 130 DEGS FOR SEQUENCING INTO LGA. SHE CALLED AND TOLD FLT ABCD, 'DSND TO 7000 FT MSL.' WE HAD NOT BEEN TOLD OF ANY SIMILAR FLT NUMBERS BEING ON THE FREQ AND CALLED TO CONFIRM THAT IT WAS 'FLT AECD DOWN TO 7000 FT MSL,' BUT DID NOT GET A RESPONSE AND ASSUMED IT WAS DUE TO HER WORKLOAD. WE REACHED 7000 FT AND WERE FOLLOWING HER VECTORS. WHEN SHE GAVE APCH INSTRUCTIONS TO FLT ABCD, WE STILL HAD NOT BEEN INFORMED THAT THEY WERE ON THE FREQ. BEFORE WE COULD RESPOND TO CORRECT THE CTLR THAT OUR FLT NUMBER WAS IN FACT AECD, FLT ABCD ACCEPTED THE INSTRUCTIONS TO JOIN THE APCH TO RWY 4 IN LGA. AS SOON AS WE REALIZED THE ERROR, WE CONTACTED APCH AND NOTIFIED THEM OF OUR ALT AND BEGAN TO CLB BACK TO 9000 FT. HER ONLY RESPONSE WAS 'I KNOW,' WITHOUT ANY INSTRUCTION ON WHAT ALT SHE WANTED US TO RETURN TO. AS WE WERE PASSING THROUGH ABOUT 7500 FT MSL, SHE INSTRUCTED US TO RETURN TO 7000 FT. ROUGHLY 20-30 SECONDS (SEEMED A LOT LONGER). WE RETURNED TO 7000 FT MSL AND WERE HANDED OFF TO 2 MORE FREQS BEFORE ANY CTLR NOTIFIED US THAT WE WERE FOLLOWING CHQ FLT #ABCD INTO LGA AND TO BE AWARE OF SIMILAR CALL SIGNS. WE CONTINUED THE FLT WITHOUT INCIDENT.

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.