Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 16
Airspace Violation All Types; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Separated Traffic
Human Factors; Procedure; Aircraft
Aircraft X; conducting; as I understand it; air sampling research over the front range of the Rockies in the vicinity of Denver; was flying north-south lines west of the city. These lines take it across busy departure and enroute corridors at an altitude that puts it in potential conflict with eastbound departures out of ski country airports; as well as east and westbound enroute aircraft. Because of its proximity to the Denver International Airport; the airspace is complex; at the time of the event both aircraft were less than five miles from a point at which four sectors intersect. This area requires frequent coordination between those and several other sectors in near proximity. Most of Aircraft X's route was contained in Sector 61's airspace; so I think Sector 7; at which 61 was combined; kept communications with Aircraft X and pointed the aircraft out to the other sectors. I received a point out on Aircraft X; but did not request specifics about what the aircraft was doing as we had seen these operations for a week and knew in general how they operated; although; please note this point; the aircraft does not adhere to flight planned lines and; as I now know; can be unpredictable. I don't know; even had I requested details that I would have been prepared for what Aircraft X did. Aircraft Y departed ASE; a ski country airport; eastbound to TEB. The aircraft's route took it just north of Sector 14's boundary with Sector 5 before it entered Sector 34's airspace just north of Sector 61; with Aircraft X northbound in 61's airspace. Sector 5 cleared Aircraft Y to FL330 below a westbound aircraft at FL340 and handed off to me. I took the handoff and immediately initiated handoff to 34; utilizing Automated Information Transfer procedures; as we often do in that area; thinking Aircraft Y would not clear the opposite direction in time for me to issue further climb before 34's airspace and avoid conflict with Aircraft X. Aircraft X; in the meantime; turned northeast and appeared no longer to be a factor. I will also say that I expected Aircraft X would proceed further north then he did in the end. Aircraft X was nowhere near his flight-planned route line; being some sixty miles north of a line that went south; then west and north; and Aircraft X was northeast-bound away from it. At this point; with Aircraft X northeast bound and Aircraft Y climbing better than I ordinarily expect; it looked as though there was no reason to keep Aircraft Y low. I stopped the handoff to 34; requested control for climb from 5; referencing the opposite direction traffic; and issued clearance to FL390 when it was no longer a factor. Although I had kept the data block on my scope; I was not watching Aircraft X carefully as he was now some ten miles from my airspace; northeast bound away from it. Aircraft X took a hard left turn and the two aircraft were nose-to-nose with Aircraft Y leaving FL343 for higher. I did not see the conflict until conflict alert activated; at which point I cleared Aircraft Y to turn left heading 360 and descend and maintain FL340. I received no response; so I transmitted again; this time instructing Aircraft Y to turn left heading 360 and 'start turn now.' Given that Aircraft X appeared to be in a hard left turn to proceed south on another line; and that I wanted Aircraft Y to respond immediately; and that our altitude information lags the actual altitude; this seemed the likeliest course to keep the aircraft apart. Aircraft Y read back the turn clearance; although the compliance was not as expeditious as I could have wished. Possibly because he was climbing it took time to configure the aircraft for the turn? [In the] meantime; Aircraft X appeared to take no action whatsoever to mitigate the situation; and continued to join and fly a southbound line. When I turned Aircraft Y on course he acknowledged and stated he had seen his traffic on TCAS. By this time he was in 34's airspace and I was too busy to pursue the matter further so I issued frequency change to 34 and continued working. I do not know; therefore; what role TCAS may have played in this event. Neither pilot appeared to respond to a Resolution Advisory or take any action other than as instructed. I don't know if Aircraft X was even aware of the situation; or if sector 61; or whoever was working Aircraft X; took any action. I did not have time to coordinate with another sector as the situation; being a head-on conflict; occurred in a very short time. 1) Aircraft X's difficult-to-predict movements create problems in predicting conflicts. Conflict probe in EDST becomes useless.2) Traffic was moderate; mostly concentrated in the middle of the sector; with complaints about ride conditions at all altitudes. Between the concentration of the traffic in a small volume of the airspace; including what; under other circumstances; would have been a beautiful 'field goal' involving four aircraft at FL360; complexity was moderately high and my attention was necessarily drawn to the center of my sector; away from the eastern corner where the conflict was developing.3) After review; I have to say I think 61 failed to perform a required point out that likely would have brought my attention to the situation. This is not to absolve myself of culpability in the event; but 61 pointed Aircraft X out to me when the aircraft was well south of my sector northbound. Once the aircraft turned northeast and headed away from my sector; it was far enough (about ten miles) that another point out would have been required once it turned back toward my boundary. I retained the data block on my scope; as mentioned above; for obvious reasons; but it would have been within the scope of my operational responsibilities to have dropped it.4) I was alone on the sector. I think the workload was enough to justify a D-side; although I don't know how easy it would have been to assess that in prospect rather than retrospect.5) Aircraft Y may not have responded to my first instruction because it was 'stepped-on' by someone asking about rides. There was some frequency congestion due to traffic volume and ride conditions.6) As I don't know exactly how TCAS may have played a role in the event; I don't know; for instance; if it may have delayed Aircraft Y's response to my instructions.7) I am old; and wonder if age related decline might be a factor. I have not experienced a spate of such incidents or any obvious signs of serious derogation in my control abilities; but; as this is my first operational error in over twenty-five years as a controller; I have to consider the possibility this is a sign of lessening awareness. Certainly; as I have gotten older I have noticed a greater impact from our irregular schedules on my alertness and sense of well-being.8) Four sectors; 5; 14; 34; and 61; were watching both aircraft; and none apparently saw the conflict before it started flashing on the scope. The complexity of coordination between sectors in that area may have inhibited full communication.9) Had I followed my original inclination and handed Aircraft Y off to Sector 34 at FL330; no untoward event would have occurred. Aircraft Y would have remained at that altitude for another forty miles or so until clear of Aircraft X and then gotten higher.10) Its possible getting more information when Sector 61 initiated the point out would have altered my decisions. I don't know how involved the Controller was in ascertaining Aircraft X's course or in exercising positive control over the aircraft's heading; so I can't assess how useful the information would have been.11) A timed climb or vector north would have ensured Aircraft Y remained clear of Aircraft X regardless of how Aircraft X flew. At the same it may have seemed like over-controlling; but; considering Aircraft X's unpredictable behavior; it would have been safer.12) Sector 61's using proper point out procedures likely would have prevented the loss of separation. This is a good demonstration of why those procedures exist in the form they do. It also brings up an important issue: Point out procedures have become sloppy in general; particularly in areas where they are frequently required; with some controllers attempting to use hand offs as a substitute for calling with point outs; or sending a data block with no verbal coordination. I wonder if this event is an example of laxity arising out of a general sense that the formality of proper point out procedures is unnecessary. On the one hand; we need to be able to support missions like Aircraft X's. On the other; we operate in an environment of positive control; in which aircraft operating in an unpredictable or random manner need to be contained in protected airspace or kept well clear of other aircraft. Aircraft X would mitigate the risk of this operation if it filed an accurate flight plan the aircraft could actually follow; and ensured that the pilot did follow it. The flight plan could be structured in such a way; using way points; as to make it modifiable during the operation without excessive disruption to Air Traffic Control. As it is; with a flight plan that appears not to include provision for the aircraft's airspace requirements in turns; and pilots who do not seem to be bound to follow their flight plan in a rigorous way; we have a random operation occurring in the middle of busy airspace at a very inconvenient altitude. Assuming such an operation continues without modification; treating it as such; like; say; random refueling; will cause controllers to give Aircraft X a much wider berth and separate from it by altitude or vectors wide; as I ought to have done. Controllers need to be rigorous in their coordination and application of proper procedures for transfer of radar identification. This is the usual ongoing issue. It's possible a d-side would have distributed the workload and allowed me to see the developing conflict sooner; or would have seen it her/himself; thereby avoiding the loss of separation. Workload contributed to this event; although; as I say above; I don't know that it was obvious at the time.
ZDV Controller reports of a conflict at altitude between two aircraft causing a loss of separation.