Narrative:

Departing mco at XA49. Cleared into position and hold on runway 18L, tower frequency 124.3. Cleared for takeoff on a 220 degree heading. First officer read back takeoff clearance and captain dialed heading into MCP. After departure, departure control advised the 'tower said everything kosher -- no problems.' we did not understand comment and queried departure and were advised to call number. Upon arrival in ord, called and were told that tower had cleared another flight for takeoff on runway 17 and that both the other aircraft and our flight read back the takeoff clearance. Tower was transmitting on both frequencys and we evidently confused the flight number and accepted the clearance. Tower did not ask us to abort the takeoff nor advise that we had erred. We never knew we accepted the wrong takeoff clearance until on the ground in ord. Tower should not be transmitting on 2 frequencys, as this was the primary cause of the confusion. Further, if tower recognized we were departing in error, they should have had us abort our takeoff since the visibility was excellent. The first officer and I spoke with the supervisor of both departure control and the tower at the time of our call. The tower supervisor who was on duty when the incident occurred was no longer on duty. Supplemental information from acn 563446: after taxiing into position and hold on runway 18L in mco, I responded to what I thought was our takeoff clearance with a heading of 200 degrees. Takeoff was normal and departure was normal. When departure control switched us to center he made a comment referencing 'everything is ok with the tower.' we queried him about this and received a phone number for mco tower. After arrival in ord, captain and I called the mco tower. We spoke with mr X at XD32. He stated that we took and read back the takeoff clearance for another flight who was in position on runway 17, and that we were not cleared for takeoff. The ground and tower frequencys in mco are spilt east and west. The tower controller was listening to each frequency separately and transmitting on both. We could not hear aircraft on the east runway. The tower controller issued a takeoff clearance to what I thought was us. I read back the takeoff clearance and the controller did not respond with 'negative, that was for another aircraft' or anything like that. We took off and had no idea of any problems until reaching ord and talking with mr X, and mr X did say that the tower tapes had both aircraft responding to the controller's takeoff clearance. We did not even know there was another aircraft in position and hold at mco or why the tower controller did not abort us.

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Original NASA ASRS Text

Title: B767 FLC AFTER DEPARTING MCO LEARN THE CLRNC WAS FOR ANOTHER ACFT WITH A SIMILAR ACFT NUMBER ON A DIFFERENT FREQ.

Narrative: DEPARTING MCO AT XA49. CLRED INTO POS AND HOLD ON RWY 18L, TWR FREQ 124.3. CLRED FOR TKOF ON A 220 DEG HDG. FO READ BACK TKOF CLRNC AND CAPT DIALED HDG INTO MCP. AFTER DEP, DEP CTL ADVISED THE 'TWR SAID EVERYTHING KOSHER -- NO PROBS.' WE DID NOT UNDERSTAND COMMENT AND QUERIED DEP AND WERE ADVISED TO CALL NUMBER. UPON ARR IN ORD, CALLED AND WERE TOLD THAT TWR HAD CLRED ANOTHER FLT FOR TKOF ON RWY 17 AND THAT BOTH THE OTHER ACFT AND OUR FLT READ BACK THE TKOF CLRNC. TWR WAS XMITTING ON BOTH FREQS AND WE EVIDENTLY CONFUSED THE FLT NUMBER AND ACCEPTED THE CLRNC. TWR DID NOT ASK US TO ABORT THE TKOF NOR ADVISE THAT WE HAD ERRED. WE NEVER KNEW WE ACCEPTED THE WRONG TKOF CLRNC UNTIL ON THE GND IN ORD. TWR SHOULD NOT BE XMITTING ON 2 FREQS, AS THIS WAS THE PRIMARY CAUSE OF THE CONFUSION. FURTHER, IF TWR RECOGNIZED WE WERE DEPARTING IN ERROR, THEY SHOULD HAVE HAD US ABORT OUR TKOF SINCE THE VISIBILITY WAS EXCELLENT. THE FO AND I SPOKE WITH THE SUPVR OF BOTH DEP CTL AND THE TWR AT THE TIME OF OUR CALL. THE TWR SUPVR WHO WAS ON DUTY WHEN THE INCIDENT OCCURRED WAS NO LONGER ON DUTY. SUPPLEMENTAL INFO FROM ACN 563446: AFTER TAXIING INTO POS AND HOLD ON RWY 18L IN MCO, I RESPONDED TO WHAT I THOUGHT WAS OUR TKOF CLRNC WITH A HDG OF 200 DEGS. TKOF WAS NORMAL AND DEP WAS NORMAL. WHEN DEP CTL SWITCHED US TO CTR HE MADE A COMMENT REFING 'EVERYTHING IS OK WITH THE TWR.' WE QUERIED HIM ABOUT THIS AND RECEIVED A PHONE NUMBER FOR MCO TWR. AFTER ARR IN ORD, CAPT AND I CALLED THE MCO TWR. WE SPOKE WITH MR X AT XD32. HE STATED THAT WE TOOK AND READ BACK THE TKOF CLRNC FOR ANOTHER FLT WHO WAS IN POS ON RWY 17, AND THAT WE WERE NOT CLRED FOR TKOF. THE GND AND TWR FREQS IN MCO ARE SPILT E AND W. THE TWR CTLR WAS LISTENING TO EACH FREQ SEPARATELY AND XMITTING ON BOTH. WE COULD NOT HEAR ACFT ON THE E RWY. THE TWR CTLR ISSUED A TKOF CLRNC TO WHAT I THOUGHT WAS US. I READ BACK THE TKOF CLRNC AND THE CTLR DID NOT RESPOND WITH 'NEGATIVE, THAT WAS FOR ANOTHER ACFT' OR ANYTHING LIKE THAT. WE TOOK OFF AND HAD NO IDEA OF ANY PROBS UNTIL REACHING ORD AND TALKING WITH MR X, AND MR X DID SAY THAT THE TWR TAPES HAD BOTH ACFT RESPONDING TO THE CTLR'S TKOF CLRNC. WE DID NOT EVEN KNOW THERE WAS ANOTHER ACFT IN POS AND HOLD AT MCO OR WHY THE TWR CTLR DID NOT ABORT US.

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.