Narrative:

Air carrier flight jcc headed toward rst at a position approximately 85 mi east of rst. Flight encountered turbulence and requested lower altitude. ZMP responded with 'stand by.' approximately 45 seconds later ZMP instructed 'jcc turn right 10 degrees, descend to FL290.' PNF read back, 'jcc right 10 degrees, descend to FL290.' ZMP did not respond to our readback (in the real world this is the norm rather than the exception). With no response to us (actually he continued to instruct other aircraft as though his business with us was done) we began to comply with his instructions. At 33500' ZMP asked us what our altitude was and we informed him. ZMP then told us we were not instructed to descend. We responded by telling him that we read back the descent instructions as we heard them. He made no comment, but did tell us to continue our descent to FL310. No further comments were made in flight. On the ground in msp, crew called ZMP. I talked with the sector supervisor (name). He explained that although msp was talking to us, we were still in ord center airspace and that the controllers were too busy coordinating our change of altitude with ord to explain anything to us in flight (although we never made an issue of it in flight because by the time we realized what had happened, it was a done deed and there was no sense talking about it further on the radio). He then went on to say that there was 1) no problem, 2) no alarm for airspace encroachment, and 3) the airspace was indeed clear so there was no imminent danger. I then talked to controller (name) who it appeared was doing some instructing at the time. He said he had a trnee working the position with him. He said, 'it was entirely our mistake.' they had indeed heard the incorrect read back of a clearance by us, but apparently were too busy to respond (or at least that they were too busy was my conclusion). He said the clearance was for another aircraft on the judas arrival and that he did not respond to the clearance--only us. I repeat that controller did hear us respond, but no one on that position came back and told us it was not our clearance. He did say that there was flight jgc and icc on same frequency. Conclusion: we were not advised of similar sounding call signs. We asked for lower and we were waiting to hear our call sign and instructions for lower--a set up if there are similar call signs. We read back the clearance and they heard it, but did not correct our misunderstanding--a real puzzlement to me. The majority of the controllers I hear only acknowledge a read back when it is incorrect, therefore silence or their continuing to control other aircraft is often perceived as the read back was correct. Maybe all carriers have this problem but it seems as though when we have our arrival or departure push at these hub airports, there are always a lot of similar sounding call sings--easy for marketing, bad for us.

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Original NASA ASRS Text

Title: SIMILAR CALL SIGNS RESULTED IN ACR ACCEPTING AND READING BACK A DESCENT CLRNC WHICH CTLR MEANT FOR ANOTHER ACR. OPERATIONAL DEVIATION.

Narrative: ACR FLT JCC HEADED TOWARD RST AT A POS APPROX 85 MI E OF RST. FLT ENCOUNTERED TURB AND REQUESTED LOWER ALT. ZMP RESPONDED WITH 'STAND BY.' APPROX 45 SECS LATER ZMP INSTRUCTED 'JCC TURN RIGHT 10 DEGS, DSND TO FL290.' PNF READ BACK, 'JCC RIGHT 10 DEGS, DSND TO FL290.' ZMP DID NOT RESPOND TO OUR READBACK (IN THE REAL WORLD THIS IS THE NORM RATHER THAN THE EXCEPTION). WITH NO RESPONSE TO US (ACTUALLY HE CONTINUED TO INSTRUCT OTHER ACFT AS THOUGH HIS BUSINESS WITH US WAS DONE) WE BEGAN TO COMPLY WITH HIS INSTRUCTIONS. AT 33500' ZMP ASKED US WHAT OUR ALT WAS AND WE INFORMED HIM. ZMP THEN TOLD US WE WERE NOT INSTRUCTED TO DSND. WE RESPONDED BY TELLING HIM THAT WE READ BACK THE DSCNT INSTRUCTIONS AS WE HEARD THEM. HE MADE NO COMMENT, BUT DID TELL US TO CONTINUE OUR DSCNT TO FL310. NO FURTHER COMMENTS WERE MADE IN FLT. ON THE GND IN MSP, CREW CALLED ZMP. I TALKED WITH THE SECTOR SUPVR (NAME). HE EXPLAINED THAT ALTHOUGH MSP WAS TALKING TO US, WE WERE STILL IN ORD CENTER AIRSPACE AND THAT THE CTLRS WERE TOO BUSY COORDINATING OUR CHANGE OF ALT WITH ORD TO EXPLAIN ANYTHING TO US IN FLT (ALTHOUGH WE NEVER MADE AN ISSUE OF IT IN FLT BECAUSE BY THE TIME WE REALIZED WHAT HAD HAPPENED, IT WAS A DONE DEED AND THERE WAS NO SENSE TALKING ABOUT IT FURTHER ON THE RADIO). HE THEN WENT ON TO SAY THAT THERE WAS 1) NO PROB, 2) NO ALARM FOR AIRSPACE ENCROACHMENT, AND 3) THE AIRSPACE WAS INDEED CLR SO THERE WAS NO IMMINENT DANGER. I THEN TALKED TO CTLR (NAME) WHO IT APPEARED WAS DOING SOME INSTRUCTING AT THE TIME. HE SAID HE HAD A TRNEE WORKING THE POS WITH HIM. HE SAID, 'IT WAS ENTIRELY OUR MISTAKE.' THEY HAD INDEED HEARD THE INCORRECT READ BACK OF A CLRNC BY US, BUT APPARENTLY WERE TOO BUSY TO RESPOND (OR AT LEAST THAT THEY WERE TOO BUSY WAS MY CONCLUSION). HE SAID THE CLRNC WAS FOR ANOTHER ACFT ON THE JUDAS ARR AND THAT HE DID NOT RESPOND TO THE CLRNC--ONLY US. I REPEAT THAT CTLR DID HEAR US RESPOND, BUT NO ONE ON THAT POS CAME BACK AND TOLD US IT WAS NOT OUR CLRNC. HE DID SAY THAT THERE WAS FLT JGC AND ICC ON SAME FREQ. CONCLUSION: WE WERE NOT ADVISED OF SIMILAR SOUNDING CALL SIGNS. WE ASKED FOR LOWER AND WE WERE WAITING TO HEAR OUR CALL SIGN AND INSTRUCTIONS FOR LOWER--A SET UP IF THERE ARE SIMILAR CALL SIGNS. WE READ BACK THE CLRNC AND THEY HEARD IT, BUT DID NOT CORRECT OUR MISUNDERSTANDING--A REAL PUZZLEMENT TO ME. THE MAJORITY OF THE CTLRS I HEAR ONLY ACKNOWLEDGE A READ BACK WHEN IT IS INCORRECT, THEREFORE SILENCE OR THEIR CONTINUING TO CTL OTHER ACFT IS OFTEN PERCEIVED AS THE READ BACK WAS CORRECT. MAYBE ALL CARRIERS HAVE THIS PROB BUT IT SEEMS AS THOUGH WHEN WE HAVE OUR ARR OR DEP PUSH AT THESE HUB ARPTS, THERE ARE ALWAYS A LOT OF SIMILAR SOUNDING CALL SINGS--EASY FOR MARKETING, BAD FOR US.

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.