Narrative:

Our flight, air carrier X ddg, was being vectored for approach to runway 27R at ord. Another air carrier X flight with similar call sign (cdg) was on the same frequency. We had shared frequencys with that flight all the way from sea to ord. We were at 7000' MSL, 210 KTS (assigned), heading 080 degrees. I heard 'air carrier X ddg heavy descend to 4000, slow to 170 KTS.' I read back the clearance verbatim. When we reached 6350' we were ordered to 'level off,' and told we were supposed to be at 7000'. We leveled off at 6300' and I told the controller we had been cleared to 4000'. He said that clearance had been for air carrier X cdg. A new controller then came on the frequency and annunciated all the #'south very carefully. I believe the main cause of this problem was controller workload and the apparent need to talk rapidly. That rapid rate of delivery makes it possible for more mistakes by both the controller and the pilot. When the second controller took over communications were very clear and I really don't believe it slowed the operation at all. Even if it did slow things down a bit, it seems like a small price to pay for the safety level. On a related subject--clearance instructions from chicago approach almost always come in rapid bursts of many instructions (slow down, descent, crossing restrictions, altitude and airspeed, tower contact place and frequency) all given in 1 breath.

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Original NASA ASRS Text

Title: ACR WDB CLRNC RESPONSE TO WRONG CALL SIGN. SIMILAR A/N SAME COMPANY.

Narrative: OUR FLT, ACR X DDG, WAS BEING VECTORED FOR APCH TO RWY 27R AT ORD. ANOTHER ACR X FLT WITH SIMILAR CALL SIGN (CDG) WAS ON THE SAME FREQ. WE HAD SHARED FREQS WITH THAT FLT ALL THE WAY FROM SEA TO ORD. WE WERE AT 7000' MSL, 210 KTS (ASSIGNED), HDG 080 DEGS. I HEARD 'ACR X DDG HVY DSND TO 4000, SLOW TO 170 KTS.' I READ BACK THE CLRNC VERBATIM. WHEN WE REACHED 6350' WE WERE ORDERED TO 'LEVEL OFF,' AND TOLD WE WERE SUPPOSED TO BE AT 7000'. WE LEVELED OFF AT 6300' AND I TOLD THE CTLR WE HAD BEEN CLRED TO 4000'. HE SAID THAT CLRNC HAD BEEN FOR ACR X CDG. A NEW CTLR THEN CAME ON THE FREQ AND ANNUNCIATED ALL THE #'S VERY CAREFULLY. I BELIEVE THE MAIN CAUSE OF THIS PROB WAS CTLR WORKLOAD AND THE APPARENT NEED TO TALK RAPIDLY. THAT RAPID RATE OF DELIVERY MAKES IT POSSIBLE FOR MORE MISTAKES BY BOTH THE CTLR AND THE PLT. WHEN THE SECOND CTLR TOOK OVER COMS WERE VERY CLR AND I REALLY DON'T BELIEVE IT SLOWED THE OPERATION AT ALL. EVEN IF IT DID SLOW THINGS DOWN A BIT, IT SEEMS LIKE A SMALL PRICE TO PAY FOR THE SAFETY LEVEL. ON A RELATED SUBJECT--CLRNC INSTRUCTIONS FROM CHICAGO APCH ALMOST ALWAYS COME IN RAPID BURSTS OF MANY INSTRUCTIONS (SLOW DOWN, DSCNT, XING RESTRICTIONS, ALT AND AIRSPD, TWR CONTACT PLACE AND FREQ) ALL GIVEN IN 1 BREATH.

Data retrieved from NASA's ASRS site as of August 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.