Cessna 425/441 Conquest I/Conquest II
Air Traffic Control Developmental
Distraction; Situational Awareness; Training / Qualification
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew FLC complied w / Automation / Advisory
Human Factors; Procedure
I was training on AUS Final's with my primary trainer. It was our first session for the day and first arrival rush of the day. A steady stream of arrivals from the east and northeast were merging into one downwind. There were also multiple VFRs coming inbound from different angles. Additionally there was a few photo taking aircraft in the area. One was Aircraft X taking photos at 055 from 20 miles south of AUS to 25 miles north of AUS. He was west of the downwind overflying my airspace in communication with AUS East. Aircraft Z checked in at 068 descending to 060 on a 260 heading for RY 35L. On that heading he would be able to establish on a ten mile final and the only traffic for him was small VFRs landing RY 35R and one P28A doing an IFR ILS approach to RY35R already at 021. I descended Aircraft Z to 035; more than thousand feet above anyone he would need to over fly. Next on frequency was Aircraft Y. He was already established in the downwind at 078 descending to 070. On initial contact I continued his descent to 050; Aircraft Z had descended enough that there was 013 feet vertical separation. There was about 14 miles between the two aircraft which were on a 90 degree angle to each other. Multiple times in the past that same setup has worked where Aircraft Z would continue descent and would have more than needed vertical separation before losing vertical. I then got busy working out the sequence closer to the airport; wherein a VFR had turned wide and was going to have an issue with faster traffic coming in. As I was sorting that out and clearing the aforementioned P28A for the ILS; Aircraft Z slowed his rate of descent. I noticed this and tried to have him expedite descent. My trainer decided that was not going to be sufficient and turned the [Aircraft Y and Aircraft Z] to try and maintain degrees divergence or lateral separation. Unfortunately he seemed to have forgotten about Aircraft X point out. His turn put Aircraft Y towards Aircraft X at 055 while the Aircraft Y was at 052 leveling 050. He realized this quickly and tried to continue the descent but Aircraft Y got an RA from Aircraft X and descended further. Once Aircraft Y was able to return to ATC control he was vectored to final and cleared for a visual approach. Both Aircraft Y and Aircraft Z landed without incident. I was informed later that AUS East tried to turn the Aircraft X but he refused that instruction as he was taking photos on a set bearing and did not want to deviate.I could have issued traffic to the Aircraft Z when they were about 10 miles apart so that he would know to continue his descent at the rate expected. I could have waited a little longer before descending Aircraft Y; which would have lengthen his downwind most likely but would have kept vertical easier. Had I sequenced the VFRs better I wouldn't have been working that out and might have seen the poor rate of descent by Aircraft Z sooner. When I noticed the issue I should have turned Aircraft Y east to pass behind Aircraft Z in addition to trying to salvage vertical separation. There were no aircraft to the east of Aircraft Z and if Aircraft Y had turned behind him it would have only required a point out to AUS East.
[Report narrative contained no additional information.]
AUS TRACON Trainer and Trainee reported turning an aircraft for sequencing and separation. The vector placed the aircraft in confliction with a VFR aircraft operating a photo mission.