Narrative:

Our small aircraft X was cleared to take position and hold on runway 13R. In the process of taking the runway, I reviewed with the student pretkof planning and engine out procedures. During or near the end of this process I thought I heard the clearance for 'small aircraft X' to depart immediately, 'traffic on short final.' I read back the clearance, but only to myself as a malfunction in my intercom 'push to talk' switch was apparently broadcasting carrier only, no voice. This was determined later when trying to contact ATC. Takeoff proceeded normally. The small aircraft Y departing from alpha 9 was in visual contact, and I knew I had made a mistake. Less instruction during this critical time, and a complete preflight of the communications to be used would have removed most of the contributing factors in this situation. In addition, instructions pertaining to the clearance to taxi into position and hold included information regarding the aircraft at alpha 9, and waiting for that departure.

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Original NASA ASRS Text

Title: CLRNC EXPECTED CREATES AN UNAUTH TKOF ON OCCUPIED RWY EVEN AFTER THE TA WAS GIVEN. TFC SIGHTED.

Narrative: OUR SMA X WAS CLRED TO TAKE POS AND HOLD ON RWY 13R. IN THE PROCESS OF TAKING THE RWY, I REVIEWED WITH THE STUDENT PRETKOF PLANNING AND ENG OUT PROCS. DURING OR NEAR THE END OF THIS PROCESS I THOUGHT I HEARD THE CLRNC FOR 'SMA X' TO DEPART IMMEDIATELY, 'TFC ON SHORT FINAL.' I READ BACK THE CLRNC, BUT ONLY TO MYSELF AS A MALFUNCTION IN MY INTERCOM 'PUSH TO TALK' SWITCH WAS APPARENTLY BROADCASTING CARRIER ONLY, NO VOICE. THIS WAS DETERMINED LATER WHEN TRYING TO CONTACT ATC. TKOF PROCEEDED NORMALLY. THE SMA Y DEPARTING FROM ALPHA 9 WAS IN VISUAL CONTACT, AND I KNEW I HAD MADE A MISTAKE. LESS INSTRUCTION DURING THIS CRITICAL TIME, AND A COMPLETE PREFLT OF THE COMS TO BE USED WOULD HAVE REMOVED MOST OF THE CONTRIBUTING FACTORS IN THIS SITUATION. IN ADDITION, INSTRUCTIONS PERTAINING TO THE CLRNC TO TAXI INTO POS AND HOLD INCLUDED INFO REGARDING THE ACFT AT ALPHA 9, AND WAITING FOR THAT DEP.

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.