Narrative:

I was flying on a VFR flight following when I was handed off to marshall gca. When I contacted gca I stated position and that I was descending to 3JC for landing. I was advised 2 military helicopters in the area and a another aircraft in the area on marshall tower frequency. I had the military helicopters in sight; but not the other aircraft. I leveled at traffic pattern altitude (2100 ft AGL) and was told to squawk VFR and go to advisory at 6 miles from the airport. I quickly advised junction city traffic I was 5 miles to the west of cross midfield to enter left downwind runway 18. I was expecting a report from the helicopter since they were out of marshall tower's airspace; but I heard nothing. I noticed the helicopter staying ahead at same altitude on a collision course. I immediately banked and pulled back hard on the yoke to avoid the collision. I would say we were within 100-200 ft at the closest point. I again reported on CTAF my position and intentions and heard nothing at all from the helicopter pilots. I contacted gca on the ground to see who had control of the airspace and they stated they have no control; but offer advisories. Marshall tower does not have control either. Runway 31C is class G; and using 122.8 for communication the helicopter pilots are used to calling marshall tower since they routinely fly through the airspace and marshall gca is new; and not well known. After discussing the near miss with the helicopter pilots they stated they were on tower and 'getting ready to switch to CTAF.' they had no advisories from tower even though talking to gca moments ago. The problem is that there are 3 frequencies and 2 airports within 5 miles. Aircraft are moving far to fast for multiple changes; and to be able to keep separation from all the high volume military traffic and general aviation traffic on separate frequencies is impossible. We have to be able to talk to each other. The helicopter should have been on CTAF; but I can see there will be faster problems as military traffic continues to increase.

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Original NASA ASRS Text

Title: VFR light twin on flight following with Marshal GCA; experienced NMAC with military helicopters at 2100 FT; alleging new GCA (ATC) procedures results in having conflicting aircraft on three different frequencies.

Narrative: I was flying on a VFR flight following when I was handed off to Marshall GCA. When I contacted GCA I stated position and that I was descending to 3JC for landing. I was advised 2 military helicopters in the area and a another aircraft in the area on Marshall Tower frequency. I had the military helicopters in sight; but not the other aircraft. I leveled at traffic pattern altitude (2100 FT AGL) and was told to squawk VFR and go to advisory at 6 miles from the airport. I quickly advised Junction City traffic I was 5 miles to the west of cross midfield to enter left downwind Runway 18. I was expecting a report from the helicopter since they were out of Marshall Tower's airspace; but I heard nothing. I noticed the helicopter staying ahead at same altitude on a collision course. I immediately banked and pulled back hard on the yoke to avoid the collision. I would say we were within 100-200 FT at the closest point. I again reported on CTAF my position and intentions and heard nothing at all from the helicopter pilots. I contacted GCA on the ground to see who had control of the airspace and they stated they have no control; but offer advisories. Marshall Tower does not have control either. Runway 31C is Class G; and using 122.8 for communication the helicopter pilots are used to calling Marshall Tower since they routinely fly through the airspace and Marshall GCA is new; and not well known. After discussing the near miss with the helicopter pilots they stated they were on Tower and 'getting ready to switch to CTAF.' They had no advisories from Tower even though talking to GCA moments ago. The problem is that there are 3 frequencies and 2 airports within 5 miles. Aircraft are moving far to fast for multiple changes; and to be able to keep separation from all the high volume military traffic and general aviation traffic on separate frequencies is impossible. We have to be able to talk to each other. The helicopter should have been on CTAF; but I can see there will be faster problems as military traffic continues to increase.

Data retrieved from NASA's ASRS site as of April 2012 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.