Date: 201703
Local time of day: 1201-1800
Location: C90.TRACON, IL
Flight conditions: VMC
Weather elements / visibility: Turbulence; Windshear
Aircraft: Citationjet (C525/C526) - CJ I / II / III / IV
Flight plan: IFR
Flight phase: Climb
Airspace: Class E C90
ATC / advisory: TRACON C90
Second aircraft: Cessna Stationair/Turbo Stationair 6
Reporter organization: Government
Reporter function: Departure; Instructor
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Other / Unknown; Situational Awareness
Second reporter function: Single Pilot; Pilot Flying
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Contributing factors: Environment - Non Weather Related; Procedure; Weather
Primary problem: Ambiguous

Narrative: I was the On-the-Job Training Instructor (OJTI) during this session. A C206 was southwest of ZZZ operating VFR at 8;500 and outside of the ORD Class B airspace. They wanted to descend because they were fighting nearly 90 knots (reported winds 298 at 89 at 6;000) of headwind. They were advised that they were outside Class B and could descend and navigate at their discretion.A C525 was a ZZZ IFR departure. I mentioned to the 1S Controller that the C206 was descending and to watch out. The C525 was handed off to us climbing to 6;000 as coordinated. My trainee continued the climb to 10;000 and issued traffic with the C206. There was no reply on the traffic call; and then my trainee issued a left turn to 180 to go behind the C206.The C206 descended far faster than either of us had anticipated with very little forward movement; approximately 40 knots ground speed. By the time the C525 replied; the pilot stated 'That was way too close for comfort;' and the C206 even keyed up and agreed. I asked both pilots; but neither said they got a TCAS RA.I had prompted my trainee to allow the C206 to navigate at their discretion since they were well outside of the Class B airspace. However; we didn't issue any control instructions to avoid this situation. I don't believe any legal separation was lost; but I feel it was poor performance on my own part.


Second narrative: While returning from a day VMC flight; PIC experienced a near miss situation with a jet. PIC was in contact with Chicago TRACON throughout all phases of flight. PIC was initially at 8;500 and experiencing 90 knot headwinds. PIC requested a descent to a lower altitude to avoid excessive headwinds. ATC instructed PIC to remain clear of the O'Hare Class B and to descend. Passing through approximately 7;000 feet; PIC caught a glimpse of movement at the 3 o'clock position. At this time PIC made a comment to the passenger that an aircraft off the right side was coming in quickly. The PIC increased the rate of descent from approximately 800 feet per minute to approximately 1;600 feet per minute. The PIC observed the other aircraft take evasive action by turning hard left and climbing. The other aircraft stated to the controller that it was a close call. PIC confirmed this by also telling the controller it was close. The controller immediately took responsibility and stated he would file his own report. PIC was clear of the Class B at the time of the incident and was previously given clearance to descend. PIC believes the extreme windy conditions were the cause of this incident. The controller acknowledged this by not anticipating the rate of descent of the PIC's aircraft.


Synopsis: A C90 Controller and one of the two pilots involved reported an airborne conflict in C90 airspace.