2010-07 · NASA ASRS report 897032
ZAU controller experienced a loss of separation event when coordination with GRR and was confused and arrival and departure traffic from MKG conflicted.
I was working the Squib and Sparta RADAR positions combined. The Assistant RADAR position was also staffed. There was Aircraft X flying from ORD to GRR at 13;000 feet. By Letter Of Agreement; Sparta descends GRR arrivals down to 9;000 feet in the Southwest corner of GRR approaches airspace; near PMM. Any GRR arrival from any other direction is descended to 11;000 feet. I think I then descended Aircraft X to 11;000 feet; upon noticing the departure of Aircraft Y off BIV. I the called the GRR controller; to APREQ either a lower altitude for Aircraft X; 9;000 feet or below; and was going to release 17;000 feet to Aircraft Y; so that GRR approach could use their air traffic rules and flip-flop the airplanes in altitude. At this point I noticed a departure off of MKG airport climbing Southbound. This was noticed during the coordination with GRR approach; so I told him I could not release higher for Aircraft Y and queried if 9;000 feet was still approved for Aircraft X. The controller stated in the affirmative and I told the controller I would call back when I had higher for Aircraft Y. I then called the MKG controller and gave instruction for the Southbound plane to be cleared to a point further down on his route of flight Southwest of where this situation was developing; therefore not becoming a factor. I call GRR approach back and released 17;000 feet on Aircraft Y with respect to Aircraft X; whom I had already transferred communications to GRR approach; and the controller read back the 17;000 feet. My traffic and complexity of the sector was increasing and as Aircraft Y checked on the frequency leveling at 10;000 feet as GRR approach was calling on the shout line and my Assistant RADAR controller was answering. I noticed that Aircraft X was descending through 11;500 feet; and due to the fact that Aircraft Y was calling on leveling at 10;000feet; I thought the GRR controller was telling my Assistant RADAR controller that he had stopped the Aircraft X at 11;000 feet and to keep Aircraft Y at 10;000 feet until separation was established. The next update was Aircraft X descending through 10;600 feet and Aircraft Y stated he was responding to an RA. I then climbed Aircraft Y up to 17;000 feet. My next clearance to Aircraft Y was to clear him direct LAN. Recommendation; If all the GRR arrivals went to 11;000 feet instead of 9;000 feet; this problem would have never occurred; especially due to the close proximity of BIV airport and MKG approach. BIV departures should not be climbed to 10;000 feet without coordination with GRR approach when there are GRR arrivals from the Southwest. This solution would as well alleviate this potentially extremely hazardous situation. MKG approach or GRR approach should take control of the airspace up to 10;000 feet in the shelf of airspace around the PMM VOR. This too; would solve this situation.
I was on the D-Side position. Aircraft X was on frequency descending from 130 to 90 direct GRR Airport. Aircraft Y departed BIV going to PTK via LAN.SPRTN3.PTK requesting 170. GRR approach owns 100 and below in the airspace; and we own 110-190. MKG approach also owns 100 and below; and is adjacent to GRR approach. MKG works the BIV departures and climbs to 100 on course. We descend the GRR arrivals to 90 per LOA; and hand off to GRR approach. The RADAR person was trying to coordinate with GRR about these two aircraft; and I thought; and still think; was giving GRR approach higher on Aircraft Y reference Aircraft X. The controller also coordinated descending to 90; even though that is LOA procedure. I assumed that GRR was separating the two aircraft; partly because of the coordination which I only heard part of; and mostly because it is in their airspace. The RADAR person had switched Aircraft X to GRR approach and then Aircraft Y checks on our frequency; not sure what altitude; but climbing to 100; which is GRR's top altitude; I was a little surprised because I thought they were separating the two aircraft; and they weren't separated yet; and that we had released 170 to GRR; I thought. Aircraft X was still above 110; so I thought maybe GRR was stopping Aircraft X at 110; and was calling to coordinate that. When they called they said that they didn't talk to Aircraft Y; and that he was only climbing to 100. I then saw an update on Aircraft X that went to 106; I think; and knew we had big problems. I asked GRR what they wanted us to do with Aircraft Y; and told the RADAR person to turn them. They were going to be close; 1 mile or so; and at approximately at the same altitude. I then heard that Aircraft Y was responding to a TCAS advisory and was climbing. Recommendation: More precise coordination; if coordination was going to be performed; or in this case if we had just followed procedures and descended to 90; and shipped to GRR; they would not have been confused as to who was responsible for separation. In this specific case; the coordination muddied the water; and I believe confused GRR approach into thinking that they were not responsible for separating aircraft in their airspace.Also; we descend to 90 which is through the top of their airspace per LOA. If we just descended to 110; and let them descend into their airspace; this event and many like them would not happen.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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