Narrative:

Training was in progress on the local control position. The developmental cleared a LR45 for takeoff from runway xx and advised the pilot to remain on runway heading and to maintain 3;000 ft. The developmental then advised a C560 to line up and wait on runway yyl and received a correct readback. The developmental then inadvertently used the C560's call sign for a clearance meant for the LR45; which was to turn right heading 190 and maintain 3;000 ft and contact departure. A readback was heard from the C560. As the ojti; I immediately keyed up and corrected the clearance using the correct call sign which was for the LR45; and transferred the aircraft to departure. A correct readback was heard from the LR45. No transmission was heard from the C560. The developmental advised me that when he used the incorrect call sign (the C560s); he had also scanned the incorrect flight strip (the C560s) into the efsts. I called on the land line to the departure controller and advised them that the C560's departure strip had incorrect runway and altitude information and that the C560 would be departing runway yyl and climbing to 5;000. While I was on the land line; the C560 called to verify that they were cleared to make a right turn to heading 190. I did not fully hear the transmission due to being on the land line. I keyed up and asked if the C560 had transmitted and as I was listening to the pilot ask about the clearance; I observed that they had departed runway yyl and were airborne. I transmitted that they should remain on runway heading and climb to 5;000 ft. I then advised that they had answered a clearance for another aircraft that had departed the crosswind runway. The pilot advised that he had heard their call sign. I did not advise the pilot that they had departed runway yyl without a takeoff clearance. Recommendation; the pilot of the C560 took off runway yyl without a takeoff clearance I assume due to the call sign confusion with the LR45. As the ojti; after I corrected the transmission the developmental made to the LR45 but using the C560's call sign; I should have stated that the clearance was not for the C560 even thought we received a correct readback from the LR45. I have no idea what clearance the C560 used to takeoff runway yyl because no takeoff clearance was ever issued.

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Original NASA ASRS Text

Title: Tower Controller described an apparent takeoff without clearance event when the Developmental Controller used incorrect aircraft call signs during the clearances.

Narrative: Training was in progress on the Local Control position. The developmental cleared a LR45 for takeoff from Runway XX and advised the pilot to remain on runway heading and to maintain 3;000 FT. The Developmental then advised a C560 to line up and wait on Runway YYL and received a correct readback. The Developmental then inadvertently used the C560's call sign for a clearance meant for the LR45; which was to turn right heading 190 and maintain 3;000 FT and contact Departure. A readback was heard from the C560. As the OJTI; I immediately keyed up and corrected the clearance using the correct call sign which was for the LR45; and transferred the aircraft to Departure. A correct readback was heard from the LR45. No transmission was heard from the C560. The Developmental advised me that when he used the incorrect call sign (the C560s); he had also scanned the incorrect flight strip (the C560s) into the EFSTS. I called on the land line to the Departure Controller and advised them that the C560's departure strip had incorrect runway and altitude information and that the C560 would be departing Runway YYL and climbing to 5;000. While I was on the land line; the C560 called to verify that they were cleared to make a right turn to heading 190. I did not fully hear the transmission due to being on the land line. I keyed up and asked if the C560 had transmitted and as I was listening to the pilot ask about the clearance; I observed that they had departed Runway YYL and were airborne. I transmitted that they should remain on runway heading and climb to 5;000 FT. I then advised that they had answered a clearance for another aircraft that had departed the crosswind runway. The pilot advised that he had heard their call sign. I did not advise the pilot that they had departed Runway YYL without a takeoff clearance. Recommendation; the pilot of the C560 took off Runway YYL without a takeoff clearance I assume due to the call sign confusion with the LR45. As the OJTI; after I corrected the transmission the Developmental made to the LR45 but using the C560's call sign; I should have stated that the clearance was not for the C560 even thought we received a correct readback from the LR45. I have no idea what clearance the C560 used to takeoff Runway YYL because no takeoff clearance was ever issued.

Data retrieved from NASA's ASRS site as of April 2012 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.