Small Transport
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 1
Time Pressure; Workload; Distraction; Confusion; Communication Breakdown; Situational Awareness
ATC Issue All Types; Conflict NMAC
Air Traffic Control Issued New Clearance
Procedure; Chart Or Publication; Human Factors
I had Aircraft X in LUAW (Line Up and Wait) Runway XX waiting for Aircraft Y to complete a Touch-N-Go Runway XXR. While the Aircraft Y was around short final Runway XXR; a Helicopter (Aircraft Z) called ready to depart from west side of the airfield. I also had 2 helicopters (Aircraft A / Aircraft B) inbound who were 2 - 2.5 miles out to land. I quickly responded to Aircraft Z to depart and proceed outbound.Based on memory; I don't recall giving Aircraft Z any traffic about Aircraft X in LUAW. My memory feels like about 1-2 minutes now have passed and Aircraft Y is now upwind Runway XXR and crossing the intersection of Runway XX. I tell Aircraft Y to continue upwind. I then clear Aircraft X for take-off Runway XX. As I'm scanning the runways watching Aircraft X start his departure rotation; I noticed a helicopter going east about to cross the departure end of Runway XX. I thought that helicopter was Aircraft A which was supposed to land and according to our Letter of Agreement (LOA); would make him restricted west of Runway XX. Finally; I reached out to Aircraft A and told them to turn base now to land. Aircraft A then responded that they were still 1 mile west. I then realized my mistake and that the helicopter crossing the departure end was my helicopter outbound. I became flustered and a bit panicked and tried to reach out to that Aircraft Z; but accidentally called them the 3rd helicopter's call sign; Aircraft B; adding even more confusion to the whole scenario. At this point Aircraft X passes below Aircraft Z by maybe 50 to 100 ft. I apologize to Aircraft X about the close aircraft; he responded that he had the helicopter in sight. I then later reach out to Aircraft Z and apologize; and they said it was OK. Aircraft X did not report a RA and neither aircraft reported having to take evasive maneuvers.
A Tower Controller reported they confused call signs and locations of helicopters arriving and departing which resulted in their instructions causing a NMAC between one of the helicopters and a departing fixed wing aircraft.