Narrative:

Local controller 2 and ground control is responsible for 300 feet and below airspace in the class delta for helicopter traffic to helipads located around the airport. The local controller 1 is responsible for all inbounds/outbound to the runway. I was not working local control 1. The local control 1 controller had a GA helicopter inbound in which the pilot conducted an un-anticipated short approach. No known restriction was given to helicopter (usually instructed to stay at or above 500 feet AGL until final to remain above local control 2 traffic.)aircraft X descended left base through final for local control 2's traffic to helipads in front of aircraft Y. Aircraft Y was issued traffic; although I was not in communication with aircraft X and did not coordinate for descent in local 2's airspace. Aircraft Y did not respond nor were any visual evasive maneuvers observed. Aircraft X was then given a clearance to land on the northern helipads located on the airport. (Used for general aviation helicopters only). Aircraft X was visually observed descending towards the helipad from final. One minute passed and I scanned the north ramp and did not see aircraft X at the correct helipad. The controller in charge who was also working local control 1 received a phone call from a nearby operator that aircraft X has landed on their helipads. Aircraft X [had] landed in their helipads. Situation was resolved; aircraft X flew direct to the correct helipads. I did not receive any communication from any of the traffic I had on frequency nor observed any abnormal maneuvers. I believe that the local 1 controller did not use the prescribed technique of restricting aircraft X at or above 500 feet until final; as this is a standard technique used by our facility. I also believe that the pilot of aircraft X did a short approach without notifying the local 1 controller. These two communication errors would have prevented this. However; once the situation presented itself; climbing aircraft X out of local 2's airspace would have been the best solution.

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Original NASA ASRS Text

Title: GCN Tower Controller reported a NMAC between a helicopter flying through their airspace without coordination and into conflict with another helicopter.

Narrative: Local Controller 2 and Ground Control is responsible for 300 feet and below airspace in the Class Delta for helicopter traffic to helipads located around the airport. The Local Controller 1 is responsible for all inbounds/outbound to the runway. I was not working Local Control 1. The Local Control 1 controller had a GA helicopter inbound in which the pilot conducted an un-anticipated short approach. No known restriction was given to helicopter (usually instructed to stay at or above 500 feet AGL until final to remain above Local Control 2 traffic.)Aircraft X descended left base through final for Local Control 2's traffic to helipads in front of Aircraft Y. Aircraft Y was issued traffic; although I was not in communication with Aircraft X and did not coordinate for descent in Local 2's airspace. Aircraft Y did not respond nor were any visual evasive maneuvers observed. Aircraft X was then given a clearance to land on the northern helipads located on the airport. (Used for General Aviation helicopters only). Aircraft X was visually observed descending towards the helipad from final. One minute passed and I scanned the north ramp and did not see Aircraft X at the correct helipad. The Controller in Charge who was also working Local Control 1 received a phone call from a nearby Operator that Aircraft X has landed on their helipads. Aircraft X [had] landed in their helipads. Situation was resolved; Aircraft X flew direct to the correct helipads. I did not receive any communication from any of the traffic I had on frequency nor observed any abnormal maneuvers. I believe that the Local 1 Controller did not use the prescribed technique of restricting Aircraft X at or above 500 feet until final; as this is a standard technique used by our facility. I also believe that the pilot of Aircraft X did a short approach without notifying the Local 1 controller. These two communication errors would have prevented this. However; once the situation presented itself; climbing Aircraft X out of Local 2's airspace would have been the best solution.

Data retrieved from NASA's ASRS site 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.