Narrative:

While operating air carrier xbcd and receiving radar vectors for a converging runway 9R ILS at kphl, we were issued the following clearance: 'air carrier xbcd, turn to 210 degrees, descend to 6000 ft.' our reply was: '210 degree heading, leaving 8000 for 6000, air carrier xbcd.' I, the PNF then changed the altitude alerter to 6000 ft, pointed to it, and waited for the PF to also point to the 6000 ft in the window of the alerter (which he did). Shortly thereafter, while in our descent to 6000 ft, we were notified by approach: 'air carrier xbcd, your assigned altitude is 8000 ft' (interference). The PNF then responded: 'air carrier xbcd was given a heading of 210 degrees and a descent to 6000 ft, which we read back.' there was a long period of silence (during which everyone was looking at TCASII, I'm sure) followed by the controller stating there was an air carrier xdcd on frequency with a similar sounding call sign. To preclude any further error, we then responded with 'air carrier ex be see dee versus 'air carrier xbcd.' fortunately, there was no conflict. Because both pilots heard 'air carrier xbcd..' and both pilots verified the assigned altitude of 6000 ft by pointing to it in the alerter window, I'm certain the controller issued us a clearance he meant for air carrier xdcd, and didn't catch his error in our readback. (Typical pilot response -- blame the controller, right?!) regardless, I'm very pleased we have our altitude verification procedure at air carrier and would certainly encourage other operators to adopt it even if it seems silly at first.

Google
 

Original NASA ASRS Text

Title: FLC DSNDS TO WRONG ALT AS PER CLRNC TO ANOTHER AIRPLANE WITH A SIMILAR CALL SIGN.

Narrative: WHILE OPERATING ACR XBCD AND RECEIVING RADAR VECTORS FOR A CONVERGING RWY 9R ILS AT KPHL, WE WERE ISSUED THE FOLLOWING CLRNC: 'ACR XBCD, TURN TO 210 DEGS, DSND TO 6000 FT.' OUR REPLY WAS: '210 DEG HDG, LEAVING 8000 FOR 6000, ACR XBCD.' I, THE PNF THEN CHANGED THE ALT ALERTER TO 6000 FT, POINTED TO IT, AND WAITED FOR THE PF TO ALSO POINT TO THE 6000 FT IN THE WINDOW OF THE ALERTER (WHICH HE DID). SHORTLY THEREAFTER, WHILE IN OUR DSCNT TO 6000 FT, WE WERE NOTIFIED BY APCH: 'ACR XBCD, YOUR ASSIGNED ALT IS 8000 FT' (INTERFERENCE). THE PNF THEN RESPONDED: 'ACR XBCD WAS GIVEN A HDG OF 210 DEGS AND A DSCNT TO 6000 FT, WHICH WE READ BACK.' THERE WAS A LONG PERIOD OF SILENCE (DURING WHICH EVERYONE WAS LOOKING AT TCASII, I'M SURE) FOLLOWED BY THE CTLR STATING THERE WAS AN ACR XDCD ON FREQ WITH A SIMILAR SOUNDING CALL SIGN. TO PRECLUDE ANY FURTHER ERROR, WE THEN RESPONDED WITH 'ACR EX BE SEE DEE VERSUS 'ACR XBCD.' FORTUNATELY, THERE WAS NO CONFLICT. BECAUSE BOTH PLTS HEARD 'ACR XBCD..' AND BOTH PLTS VERIFIED THE ASSIGNED ALT OF 6000 FT BY POINTING TO IT IN THE ALERTER WINDOW, I'M CERTAIN THE CTLR ISSUED US A CLRNC HE MEANT FOR ACR XDCD, AND DIDN'T CATCH HIS ERROR IN OUR READBACK. (TYPICAL PLT RESPONSE -- BLAME THE CTLR, RIGHT?!) REGARDLESS, I'M VERY PLEASED WE HAVE OUR ALT VERIFICATION PROC AT ACR AND WOULD CERTAINLY ENCOURAGE OTHER OPERATORS TO ADOPT IT EVEN IF IT SEEMS SILLY AT FIRST.

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.