Narrative:

5c1 is a fairly busy; uncontrolled airport right on the localizer about 15 mile final to sat. They have a wide variety from gliders to [corporate jets] based at 5c1. Today; as pretty much with every day; we are working a final around whatever the uncontrolled airport is doing that day guessing what altitude primary targets are at; guessing which way the gliders are going to go; wondering if the mode C is accurate. Today was no different. There was one aircraft that appeared to be doing acrobatics about 5 miles northwest of the localizer. I had varying reports of altitude between 3000 and 5000; often times mode C indicated literally right on the localizer to 13R. With the aircraft doing aerobatics on the localizer; I was taking aircraft off of the arrival and vectoring to final. As I'm vectoring aircraft X towards the final approach fix; another aircraft departed 5c1; turned to the northwest and started climbing right towards the descending aircraft X. I turned aircraft X again away from the final and called traffic. This type of operation in general makes sequencing air carriers more complicated than it needs to be and introduces a lot of guessing and hoping on what we think these aircraft are going to do. Often times; with the gliders; we do not even see the targets all of the time due to the size of the aircraft; the type of tight circle maneuvering they're doing on top of the lack of transponders. 5c1 is a well-known problem in our facility. There have been multiple reports and multiple attempts to educate the users of the airport. We have even made requests to expand our class C airspace or upgrade our airspace to class B to give us more control over the final approach course of our primary runway. I recommend to increase our airspace size to force VFR; non-participating aircraft to stay below glideslope altitudes on the ILS on the localizer so that we at least know the airspace that every aircraft landing sat will be protected while on the approach.

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Original NASA ASRS Text

Title: SAT TRACON Controller reported unsafe operations between aircraft landing Runway 13R and the nearby non-towered field 5C1.

Narrative: 5C1 is a fairly busy; uncontrolled airport right on the localizer about 15 mile final to SAT. They have a wide variety from gliders to [corporate jets] based at 5C1. Today; as pretty much with every day; we are working a final around whatever the uncontrolled airport is doing that day guessing what altitude primary targets are at; guessing which way the gliders are going to go; wondering if the mode C is accurate. Today was no different. There was one aircraft that appeared to be doing acrobatics about 5 miles northwest of the localizer. I had varying reports of altitude between 3000 and 5000; often times Mode C indicated literally right on the localizer to 13R. With the aircraft doing aerobatics on the localizer; I was taking aircraft off of the arrival and vectoring to final. As I'm vectoring Aircraft X towards the final approach fix; another aircraft departed 5C1; turned to the northwest and started climbing right towards the descending Aircraft X. I turned Aircraft X again away from the final and called traffic. This type of operation in general makes sequencing air carriers more complicated than it needs to be and introduces a lot of guessing and hoping on what we think these aircraft are going to do. Often times; with the gliders; we do not even see the targets all of the time due to the size of the aircraft; the type of tight circle maneuvering they're doing on top of the lack of transponders. 5C1 is a well-known problem in our facility. There have been multiple reports and multiple attempts to educate the users of the airport. We have even made requests to expand our class C airspace or upgrade our airspace to class B to give us more control over the final approach course of our primary runway. I recommend to increase our airspace size to force VFR; non-participating aircraft to stay below glideslope altitudes on the ILS on the localizer so that we at least know the airspace that every aircraft landing SAT will be protected while on the approach.

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.