Twin Otter DHC-6
Air Traffic Control Fully Certified
Communication Breakdown; Confusion; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict
Air Traffic Control Issued New Clearance
Airspace Structure; Human Factors; Procedure
I was working STREATOR Sector (100 and below) and talking to a Twin Otter who was leveling at 140 and getting ready to release parachute jumpers. There was a point out Data Block on the PLANO Sector's scope but I did not see a depiction of the 2 mile circle that we protect on their scope. An Embraer 170 was being worked at the PLANO Sector (110 to FL230) and was on a 340 heading descending to 140. The heading took him from 4 miles south of the 8N2 Airport right along the edge of the protected space to the northwest. I told the PLANO Controller that the Twin Otter was getting ready to release the jumpers and asked to make sure that the Embraer was staying on the heading and at 140. I informed the Twin Otter of the traffic and said that the heading he was on would just keep him clear of the jump zone. The Twin Otter asked if he should hold the jumpers and I said I didn't think it would be necessary since the assigned vector should keep the traffic clear but to not go too far to the west. The Twin Otter kept flying his southwesterly heading all the way up to the very edge of the 2 mile circle instead of turning to a different heading. As the 2 aircraft got closer and closer together; I asked if the pilot had the traffic in sight. He said he did. At this point they were same altitude and less than a mile apart. The PLANO Controller announced that the Embraer pilot had my aircraft in sight. Data Blocks were flashing and overlapping and we all saw the Embraer's altitude go lower. At first we thought it was an altitude swap with the jump aircraft but it quickly became obvious that the Embraer was descending. There was no announcement of responding to an RA and thankfully my jump aircraft held the jumpers and changed heading before he let them go. I asked the pilot if everything was OK with the jumpers and advised him that the other pilot descended on his own. He said everything was fine. I don't know if it would have changed anything but I think that there should always be a depiction of the protected airspace at both PLANO and STREATOR whenever there are parachute jump operations. I had mine up at STREATOR but I don't think the PLANO Controller was aware of how close he was getting with the Embraer. We had weather in the airspace and had been dealing with minor deviations all evening. That didn't directly affect this situation but it would have been preferable to have a little more cushion between the jump zone and the Embraer especially when the possibility of deviations existed.
ZAU Controller described a conflict TCAS RA event involving an IFR arrival aircraft in a descent and a parachute operation; the reporter suggesting that protected airspace; i.e. parachute activity area; should be depicted at all involved ATC displays.