Narrative:

Procedure at pdk is to have ground control instruct aircraft to 'monitor' local control. Local control then broadcasts 'in the blind' control instructions. I have had 2 incidents where there were similar sounding call signs on frequency but I did not know this because both had not contacted me. One incident (aircraft X and aircraft Y) occurred when I cleared aircraft X (talking to aircraft Y at runway 2R; who I had already talked to and; therefore; could use last 3 of call signs) for takeoff; not knowing that the aircraft that ground control had taken to runway 2L at intersection F was aircraft X. Situation was caught by myself as aircraft at runway 2L started to roll. Similar situation at runway 20L and runway 2L at intersection G. I cleared aircraft at runway 20L at intersection G for takeoff using full call sign. He got on runway but was not moving very fast and traffic was on final. I cleared him again for immediate takeoff traffic on final using last 3 of call sign. The aircraft at runway 20L full length had same last 3 of call sign and started to roll! I did not know he had similar sounding call sign because ground control had instructed him to monitor only and he had not called me. Potentially very tragic incident; I caught in time; luckily.

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Original NASA ASRS Text

Title: PDK LCL CTLR EXPRESSED CONCERN REGARDING FACILITY POLICY THAT REQUIRES GND CTL TO INSTRUCT ACFT TO MONITOR LCL CTL RATHER THAN CALLING THEM.

Narrative: PROC AT PDK IS TO HAVE GND CTL INSTRUCT ACFT TO 'MONITOR' LCL CTL. LCL CTL THEN BROADCASTS 'IN THE BLIND' CTL INSTRUCTIONS. I HAVE HAD 2 INCIDENTS WHERE THERE WERE SIMILAR SOUNDING CALL SIGNS ON FREQ BUT I DID NOT KNOW THIS BECAUSE BOTH HAD NOT CONTACTED ME. ONE INCIDENT (ACFT X AND ACFT Y) OCCURRED WHEN I CLRED ACFT X (TALKING TO ACFT Y AT RWY 2R; WHO I HAD ALREADY TALKED TO AND; THEREFORE; COULD USE LAST 3 OF CALL SIGNS) FOR TKOF; NOT KNOWING THAT THE ACFT THAT GND CTL HAD TAKEN TO RWY 2L AT INTXN F WAS ACFT X. SIT WAS CAUGHT BY MYSELF AS ACFT AT RWY 2L STARTED TO ROLL. SIMILAR SIT AT RWY 20L AND RWY 2L AT INTXN G. I CLRED ACFT AT RWY 20L AT INTXN G FOR TKOF USING FULL CALL SIGN. HE GOT ON RWY BUT WAS NOT MOVING VERY FAST AND TFC WAS ON FINAL. I CLRED HIM AGAIN FOR IMMEDIATE TKOF TFC ON FINAL USING LAST 3 OF CALL SIGN. THE ACFT AT RWY 20L FULL LENGTH HAD SAME LAST 3 OF CALL SIGN AND STARTED TO ROLL! I DID NOT KNOW HE HAD SIMILAR SOUNDING CALL SIGN BECAUSE GND CTL HAD INSTRUCTED HIM TO MONITOR ONLY AND HE HAD NOT CALLED ME. POTENTIALLY VERY TRAGIC INCIDENT; I CAUGHT IN TIME; LUCKILY.

Data retrieved from NASA's ASRS site as of January 2009 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.