Narrative:

The aircraft X was on about a 2 mile final for runway 4R. Aircraft Y was on downwind for runway 4R. I told aircraft Y to continue on the downwind and I would call his base. I had numerous aircraft on frequency and aircraft Y did not respond. I had other transmissions to make. I failed to go back to aircraft Y and get a verification that he would actually continue in the downwind. I had planned on him being number three. This is obviously the beginning of the event. Aircraft Y turned base and was flying directly toward aircraft X on final. When I saw this I told aircraft X to execute a right 360; I actually meant to tell aircraft Y to execute the 360. Aircraft X executed a right turn to the southeast; and aircraft Y also executed a 360 although he was not given instruction to do so. Even though I told aircraft X to execute the turn instead of aircraft Y; this would have resolved the issue if aircraft Y had just turned to final as he would have been behind aircraft X. When aircraft Y made the right 360 on his own he came in an even closer proximity to aircraft X. Management told me aircraft X was the pilot that questioned the event. Both aircraft were directed back the downwind and sequenced to the runway 4R and landed without further incident. I need to make sure I get confirmation of instructions from all aircraft; that was my mistake; and I need to be more accurate with my instructions; although my inadvertent plan was better than my initial plan. I don't know what to do about student pilots making panic maneuvers on their own.

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Original NASA ASRS Text

Title: Tower Controller described a pattern conflict event when issuing a circle instruction to the wrong aircraft followed immediately by a circle initiated by a second aircraft compounding the conflict.

Narrative: The Aircraft X was on about a 2 mile final for Runway 4R. Aircraft Y was on downwind for Runway 4R. I told Aircraft Y to continue on the downwind and I would call his base. I had numerous aircraft on frequency and Aircraft Y did not respond. I had other transmissions to make. I failed to go back to Aircraft Y and get a verification that he would actually continue in the downwind. I had planned on him being number three. This is obviously the beginning of the event. Aircraft Y turned base and was flying directly toward Aircraft X on final. When I saw this I told Aircraft X to execute a right 360; I actually meant to tell Aircraft Y to execute the 360. Aircraft X executed a right turn to the southeast; and Aircraft Y also executed a 360 although he was not given instruction to do so. Even though I told Aircraft X to execute the turn instead of Aircraft Y; this would have resolved the issue if Aircraft Y had just turned to final as he would have been behind Aircraft X. When Aircraft Y made the right 360 on his own he came in an even closer proximity to Aircraft X. Management told me Aircraft X was the pilot that questioned the event. Both aircraft were directed back the downwind and sequenced to the Runway 4R and landed without further incident. I need to make sure I get confirmation of instructions from all aircraft; that was my mistake; and I need to be more accurate with my instructions; although my inadvertent plan was better than my initial plan. I don't know what to do about student pilots making panic maneuvers on their own.

Data retrieved from NASA's ASRS site as of July 2013 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.