EMB ERJ 170/175 ER/LR
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 5
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance
Human Factors; Procedure
Aircraft X descending via the LDORA STAR for 34R and Aircraft Y descending via the BOSSS STAR. Aircraft X did not execute the STAR correctly and went through the localizer and was pointed right at Aircraft Y. I turned both aircraft and Aircraft X advised he was in TCAS RA and was climbing. Both aircraft were given the ILS 34R. If replayed [another B737] who was two planes ahead of Aircraft X did the exact same thing. At the time I was watching Aircraft X the whole way in since the sequence was going to be tight. There was no possible way I could have reacted any quicker. We have an RNAV 'descend via' structure that connects to ILS transitions. We also use RNP AR approaches from the downwind. We need RNAV transitions from the RNAV STARs to RNAV approaches for the short side stars. If the structure was RNP AR descent rate would be more efficient and more accurate than an ILS transition that is probably being hand flown. Aircraft routinely come off the ILS transitions and we watch the crew try to figure out how; or tell them how to resume it. This causes us extra workload and makes it more difficult to run the sequence. We very rarely see blunders off an RNP AR if the crew was expecting the procedure. Making an RNAV structure that works like the RNP approaches from the downwinds would mitigate or solve this issue.
D01 Approach Controller reported a track deviation occurred on the LDORA STAR arrival into DEN. Reporter stated this is not unusual and stressed the need for RNAV transitions from RNAV STARs to RNAV approaches to minimize these occurrences.