Narrative:

I was working ground control position. An aircraft called for taxi for takeoff. I taxied small aircraft xo to the active runway. Subsequently small aircraft X7 departed IFR west/O a release from approach control and 1-2 mins later a small transport Z jet also IFR but with a release departed. The error was discovered when both planes popped up on approachs radar. Upon review of the tapes it appears the small aircraft xo I taxied out was in fact small aircraft X7 and therefore I did not pass on this IFR outbnd to local control and he then departed west/O a release from approach control. The problem arose because I thought I heard small aircraft xo when in fact the pilot said small aircraft X7. If I could have listened more intently I should have caught the error. Possible contributing factors could be: the tower cabin is a noisy environment with other people talking to aircraft, the pilot did not catch or correct me calling him by the wrong call sign, the pilot never stated to me or local control that he was IFR, even when he was asked by local his direction of flight all he said was 325. When I reviewed the tape the first time I still thought he said small aircraft xo, but the second time through I did hear small aircraft X7. If at the time I was unsure I should have asked the pilot to repeat, but I thought I knew what I heard.

Related reports:

Google
 

Original NASA ASRS Text

Title: TRANSPOSITION OF ACFT #'S RESULTED IN AN IFR ACFT BEING RELEASED BY MISTAKE AND CONFLICTED WITH ANOTHER IFR ACFT.

Narrative: I WAS WORKING GND CTL POS. AN ACFT CALLED FOR TAXI FOR TKOF. I TAXIED SMA XO TO THE ACTIVE RWY. SUBSEQUENTLY SMA X7 DEPARTED IFR W/O A RELEASE FROM APCH CTL AND 1-2 MINS LATER A SMT Z JET ALSO IFR BUT WITH A RELEASE DEPARTED. THE ERROR WAS DISCOVERED WHEN BOTH PLANES POPPED UP ON APCHS RADAR. UPON REVIEW OF THE TAPES IT APPEARS THE SMA XO I TAXIED OUT WAS IN FACT SMA X7 AND THEREFORE I DID NOT PASS ON THIS IFR OUTBND TO LCL CTL AND HE THEN DEPARTED W/O A RELEASE FROM APCH CTL. THE PROB AROSE BECAUSE I THOUGHT I HEARD SMA XO WHEN IN FACT THE PLT SAID SMA X7. IF I COULD HAVE LISTENED MORE INTENTLY I SHOULD HAVE CAUGHT THE ERROR. POSSIBLE CONTRIBUTING FACTORS COULD BE: THE TWR CABIN IS A NOISY ENVIRONMENT WITH OTHER PEOPLE TALKING TO ACFT, THE PLT DID NOT CATCH OR CORRECT ME CALLING HIM BY THE WRONG CALL SIGN, THE PLT NEVER STATED TO ME OR LCL CTL THAT HE WAS IFR, EVEN WHEN HE WAS ASKED BY LCL HIS DIRECTION OF FLT ALL HE SAID WAS 325. WHEN I REVIEWED THE TAPE THE FIRST TIME I STILL THOUGHT HE SAID SMA XO, BUT THE SECOND TIME THROUGH I DID HEAR SMA X7. IF AT THE TIME I WAS UNSURE I SHOULD HAVE ASKED THE PLT TO REPEAT, BUT I THOUGHT I KNEW WHAT I HEARD.

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.