Narrative:

We (C172) were doing practice instrument approachs around orl airspace and our call sign was 'call sign xyz.' we made an ILS low approach to sfb runway 9L and gone to the missed. Sfb tower assigned turn right, heading of 180 degrees and maintain 2000 ft, then switch to mco departure. The first instruction from mco departure was to climb and maintain 2000 ft with our call sign. A few seconds later, we caught the radio call '(some call sign which actually we could not catch) xyz' followed by 'descend and maintain 3000 ft.' although that instruction was kind of confusing and did not make sense to us, we thought that was the controller's simple mistake, so that we simply replied back as 'climb and maintain 3000 ft' with our full call sign. No response from mco. But a few moments later, we heard the call sign of 'air carrier xyz,' that reminded us of our mistake for that instruction. We were going to ask to confirm when we received the instruction from mco to descend and maintain 2000 ft with traffic information. Unfortunately, we did not receive any warning from either sanford tower, or mco departure control, of the call sign similarity. Nor had we been told that our readback was wrong, although we read back to mco with our full call sign. They did not correct it. We had not known that the other aircraft was using a similar call sign until we heard theirs.

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Original NASA ASRS Text

Title: C172 TRAINING FLT ASSUMES A CLRNC INSTRUCTION IS FOR THEM BECAUSE OF THE SAME LAST 3 CALL SIGN DIGITS, BEING ACTUALLY FOR A DSNDING ACR, RESULTING IN AN NMAC WHILE BEING VECTORED FOR APCH INTO SFB BY MCO APCH.

Narrative: WE (C172) WERE DOING PRACTICE INST APCHS AROUND ORL AIRSPACE AND OUR CALL SIGN WAS 'CALL SIGN XYZ.' WE MADE AN ILS LOW APCH TO SFB RWY 9L AND GONE TO THE MISSED. SFB TWR ASSIGNED TURN R, HDG OF 180 DEGS AND MAINTAIN 2000 FT, THEN SWITCH TO MCO DEP. THE FIRST INSTRUCTION FROM MCO DEP WAS TO CLB AND MAINTAIN 2000 FT WITH OUR CALL SIGN. A FEW SECONDS LATER, WE CAUGHT THE RADIO CALL '(SOME CALL SIGN WHICH ACTUALLY WE COULD NOT CATCH) XYZ' FOLLOWED BY 'DSND AND MAINTAIN 3000 FT.' ALTHOUGH THAT INSTRUCTION WAS KIND OF CONFUSING AND DID NOT MAKE SENSE TO US, WE THOUGHT THAT WAS THE CTLR'S SIMPLE MISTAKE, SO THAT WE SIMPLY REPLIED BACK AS 'CLB AND MAINTAIN 3000 FT' WITH OUR FULL CALL SIGN. NO RESPONSE FROM MCO. BUT A FEW MOMENTS LATER, WE HEARD THE CALL SIGN OF 'ACR XYZ,' THAT REMINDED US OF OUR MISTAKE FOR THAT INSTRUCTION. WE WERE GOING TO ASK TO CONFIRM WHEN WE RECEIVED THE INSTRUCTION FROM MCO TO DSND AND MAINTAIN 2000 FT WITH TFC INFO. UNFORTUNATELY, WE DID NOT RECEIVE ANY WARNING FROM EITHER SANFORD TWR, OR MCO DEP CTL, OF THE CALL SIGN SIMILARITY. NOR HAD WE BEEN TOLD THAT OUR READBACK WAS WRONG, ALTHOUGH WE READ BACK TO MCO WITH OUR FULL CALL SIGN. THEY DID NOT CORRECT IT. WE HAD NOT KNOWN THAT THE OTHER ACFT WAS USING A SIMILAR CALL SIGN UNTIL WE HEARD THEIRS.

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.