Commercial Fixed Wing
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 29.0
Communication Breakdown; Situational Awareness; Human-Machine Interface
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Separated Traffic
Airspace Structure; Procedure; Company Policy; Human Factors
I was working Sector by myself with 12 aircraft because we do not have enough staffing. Aircraft X was descending via a STAR on the established Automated Information Transfer (AIT) procedure. [Another] Sector descends STAR arrivals via; hands off to [me]. [My] sector accepts handoff; and hands off to Approach. When Approach accepts handoff; [another] Sector ships the aircraft to Approach. On the STAR the aircraft are supposed to cross a fix at or below 21000 feet because other arrivals are descending via a STAR to 22000 feet at that point. These two procedures are separated by 5.1 miles at a common fix. That is the biggest problem. There is no extra room for any error or problem. This is not safe.I had descended Aircraft Y via a STAR. When I looked at these two aircraft; Aircraft X was at 25000 feet with 1 minute or less to make his restriction 4000 feet lower. Aircraft Y was at 25100 feet and had been descending at 6000 then 5000 feet per minute and was going to be level at 22000 feet. I told Aircraft Y to' maintain current altitude and turn 30 degrees; actually turn right heading 310'. This was a 60 to 70 degree turn one minute apart. Aircraft Y turned about two miles north and Aircraft X missed his restriction by a little over a mile and I had 5.1 miles when Aircraft X leveled at 21000 feet. Normally we would have shipped Aircraft Y to Approach before this; so two different Approach sectors would be taking to these aircraft. Even if we are still talking to one arrival; we are not talking to the other arrival so we have no way of knowing when they are not going to make any of the restrictions. I would estimate that we have at least one STAR a week miss a restriction. We need to ask ourselves; if I had done nothing; at what point does Aircraft Y get TCAS alert telling him to descend and what is Aircraft X TCAS resolution? And what would happen to the rest of our traffic in the area?The crossing restrictions on the STARs need to be moved at least 3 miles south so that we have at least 8 miles separation between the one arrival and the other arrivals. Even at 8 miles this is not a great situation but at least it gives a little more time for a pilot to still get under the traffic. It also gives us more time and more information to determine if we need to take action.
Center Air Traffic Controller reported two aircraft 'descending via' on crossing STARs were going to have less than required separation due to one aircraft not complying with its crossing restriction.