FORT RUCKER, Ala. (April 19, 2019) - Near midair collisions are a danger aviators and air traffic controllers must work together to avoid. There are a number of policies and procedures that assist both in avoiding near misses; however, if the controller or an aviator does not understand the local procedures established at a designated airfield, the consequences can be dangerous. The following addresses issues that should be avoided as well as procedures that should be followed to help prevent a similar situation from occurring.The night was going as any other while I was signed on as the ATC shift leader, behind the local controller, who was doing very well. But what happened next shows just how quickly things can go from good to bad if proper procedures aren't followed.A C-23 Sherpa called at the 20-mile fixed-wing reporting point. The controller responded with the standard phraseology and instructed the C-23 to report the five-mile ring that represented the controlled airspace. About two minutes later, a flight of UH-60s called at the required point that was one mile outside the controlled airspace. The controller again gave proper phraseology to the flight and instructed the UH-60s to report entering the controlled airspace.After giving the initial control instructions, I asked the controller what he planned on doing and if he could foresee any problems with what was about to happen. Since the C-23 was about 10 miles from the field and the UH-60s were about six miles out, I knew the helicopters were going to be first in the pattern. But with the speed of the C-23, it was going to be first to the runway.With that piece of advice, I let the ATC trainee make a control decision. He decided to have the flight of UH-60s make a straight-in approach to the parallel taxiway (Golf) to ensure proper separation and provide the most expeditious flow of air traffic. When the flight called, the controller instructed them to report short final for Golf taxiway and gave a traffic call on the inbound fixed-wing traffic. The flight read back the instructions and acknowledged the traffic call. Almost simultaneously, the C-23 called at five miles inbound. The controller gave them a standard traffic call on the UH-60 flight and informed the C-23 pilot that he would be number one to the runway, with the rotary-wing traffic landing to the parallel taxiway. The C-23 pilot then entered a right base for runway 31 as instructed and acknowledged the rotary-wing traffic and confirmed he was number one to the active runway.As the situation began to develop, I realized if the rotary-wing flight was not prepared to move to a designated location other than the taxiway after landing, the C-23 would not be able to move down that taxiway to its designated off-load point. I told the trainee to instruct the UH-60s to land north of taxiway Foxtrot on taxiway Golf to not block the only usable portion of Golf. However, the UH-60 flight did not understand the clearance.The trainee then gave supplemental instructions that Foxtrot was the taxiway closest to the forward arming and refueling point. They were to land on the parallel taxiway north of that taxiway and the FARP to ensure separation with the inbound C-23. I then made sure the UH-60s understood the instructions and located them with the night vision device to ensure they were on course for where they were instructed to land, which they were. They were coming in slowly just north of the tower. The C-23 then called on short final for 31, and I scanned the runway to ensure the landing surface was clear. After I gave the trainee the go-ahead, he issued the landing clearance.The C-23 was only seconds from touchdown when I refocused my attention on the UH-60 flight and realized they had overflown the parallel taxiway and were headed for a circling left base approach to 13. It was at this point where a split-second decision would make the difference between a lesson learned or the catastrophic loss of coalition aircraft and personnel. I quickly grabbed the handset and instructed the UH-60s to immediately side-step off the active and set down due to C-23 traffic over the approach end of runway 31. The helicopters were able to clear the runway and avoid a collision with the inbound aircraft.There were many lessons learned during this experience, and the problems we encountered can assist any aviation company in the future. Two of the biggest lessons learned pertained to airfield orientation and local control procedures. The pilots were unfamiliar with the airfield, and the controllers were not aware of this because the flight had the same call sign as the medevac flight that was stationed out of this particular airfield. Another problem that arose from this situation was the controllers used local control procedures with a flight that was not a local flight. If these two issues had been addressed prior to this incident, this near miss could have been avoided.The procedures that were taken included requiring the flight to perform closed and local traffic patterns until they were familiar with the airfield. The controllers would use more precise phraseology for approaches to Golf taxiway and, if feasible, land all transient traffic on the active runway. These procedures should be taken into account, especially when performing aviation operations in unfamiliar areas, which is a frequent occurrence with the rapid deployment of aviation assets throughout the world.Do you have a story to share? 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