Narrative:

A GLF5 was an IFR departure off of [a class D airport] to [ZZZ VOR] at 4;000 ft. A DA40 was a VFR practice approach that was direct [ZZZ VOR] from the west at 3;500 ft. A C172 was an IFR en route aircraft that was direct [ZZZ VOR]; 2 miles behind the DA40. I turned the GLF4 before [ZZZ VOR] to a 270 heading to avoid flying directly over the DA40 and to pass the C172 so I could continue his climb. Then I descended the DA40 to 30 ft because I didn't want the GLF5 to get an RA climb. Then I went back to the GLF5 and called the VFR traffic. He responded to my traffic call that he was getting an RA climb. I told him not to do that; since I had the IFR traffic at 5;000 ft behind the VFR. He told me he must respond to the RA and I told him to descend immediately to 4;000 ft. (At this point the GLF5 was past the VFR; who at this point was already level at 30 ft.) I went back and called traffic to the C172; and they told me that they had the GLF5 insight. The closest proximity during the playback of the situation was 500 ft and 1.18 miles. I'm not sure I have a recommendation; it's just one of those things that occur from time to time. I had the situation under control; I was calling traffic and keeping minimum separation; but the aircraft had to override me and listen to his equipment instead; which put him in an unsafe situation. The original situation was not unsafe; although his TCAS perceived it was. I normally use 1;000 ft separation because of this; but there are times and sectors where that isn't possible. ZZZ1 sector is approximately 10 miles by 12 miles in dimension and there are a lot of practice approaches that go on. Because of this; we use most of our available altitudes and don't always have the luxury of using 1;000 ft. In the GLF5's attempt to get 1;000 ft between him and the VFR; he went down to 500 ft separation with the IFR; placing that IFR in a risky situation for no reason. I'm upset and frustrated over the situation; but I'm not sure there is a solution.

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Original NASA ASRS Text

Title: TRACON Controller described a TCAS RA involving a VFR and IFR aircraft; the RA actions resulting in an IFR to IFR separation issue.

Narrative: A GLF5 was an IFR departure off of [a Class D airport] to [ZZZ VOR] at 4;000 FT. A DA40 was a VFR practice approach that was direct [ZZZ VOR] from the west at 3;500 FT. A C172 was an IFR en route aircraft that was direct [ZZZ VOR]; 2 miles behind the DA40. I turned the GLF4 before [ZZZ VOR] to a 270 heading to avoid flying directly over the DA40 and to pass the C172 so I could continue his climb. Then I descended the DA40 to 30 FT because I didn't want the GLF5 to get an RA climb. Then I went back to the GLF5 and called the VFR traffic. He responded to my traffic call that he was getting an RA climb. I told him not to do that; since I had the IFR traffic at 5;000 FT behind the VFR. He told me he must respond to the RA and I told him to descend immediately to 4;000 FT. (At this point the GLF5 was past the VFR; who at this point was already level at 30 FT.) I went back and called traffic to the C172; and they told me that they had the GLF5 insight. The closest proximity during the playback of the situation was 500 FT and 1.18 miles. I'm not sure I have a recommendation; it's just one of those things that occur from time to time. I had the situation under control; I was calling traffic and keeping minimum separation; but the aircraft had to override me and listen to his equipment instead; which put him in an unsafe situation. The original situation was not unsafe; although his TCAS perceived it was. I normally use 1;000 FT separation because of this; but there are times and sectors where that isn't possible. ZZZ1 Sector is approximately 10 miles by 12 miles in dimension and there are a lot of practice approaches that go on. Because of this; we use most of our available altitudes and don't always have the luxury of using 1;000 FT. In the GLF5's attempt to get 1;000 FT between him and the VFR; he went down to 500 FT separation with the IFR; placing that IFR in a risky situation for no reason. I'm upset and frustrated over the situation; but I'm not sure there is a solution.

Data retrieved from NASA's ASRS site as of July 2013 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.