Date: 202105
Local time of day: 0601-1200
Location: MDW.Airport, IL
Light: Daylight
Aircraft: Commercial Fixed Wing
Flight plan: IFR
Mission: Other unknown
Flight phase: Initial Approach
Airspace: Class E ZAU
ATC / advisory: Center ZAU
Second aircraft: Sail Plane
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Time Pressure; Situational Awareness; Workload
Anomaly: Conflict NMAC
Detector: Automation Aircraft RA; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Took Evasive Action
Contributing factors: Environment - Non Weather Related; Airspace Structure; Human Factors
Primary problem: Ambiguous

Narrative: While on the ENDEE 6 Arrival to MDW we encountered a near midair collision and the following is a narrative of that event. Time stamps are from 'Flightaware' app and may not be 100% accurate. I added these to recreate the event to the best of my knowledge.I was the Pilot Flying on this leg. At about XX:26Z ATC began to vector us off the arrival for spacing. During these vectors we were cleared to descend to lower altitudes. I had even made the comment jokingly that we were being 'over-controlled' by ATC after several heading; altitude and speed changes. At approximately XX:45Z we were cleared to descend to 5000 feet. Our flight path at the time was approximately over top of Morris Muni airport (C09) about 6.6 miles southwest of STKNY on the arrival. Crossing altitude at STKNY is published is 6000 feet. We were then cleared direct to ALQUE for the ILS 4R at MDW. While still level at 5000 feet at approximately XX:47Z we had a TCAS TA (solid amber) showing an aircraft in front of us and +100 feet above our altitude. I do not remember the scale set at the time on my navigation display but it was very 'close'. This was this first time we had seen a Traffic Advisory of any kind on the display (no open white diamond) and had not been advised of traffic from ATC. One second later ATC told us we had 'glider traffic' ahead and to 'deviate as necessary' to avoid the traffic. I immediately began a right hand descending turn. About two seconds later we received a Resolution Advisory RA to descend and the First Officer told ATC we were responding to an RA. At about 4500 feet; I saw the glider slightly higher and to our left. Once clear of the conflict; ATC cleared us to descend to 4000 feet and stated he was not in contact with the glider and asked if it was clear of clouds. ATC warned aircraft behind us on the arrival about the glider and it's altitude. We estimated the distance from the glider was 150-200 feet as it passed to our left. The event happened in the proximity of Channahon; IL Glider Club (IL59) south of STKNY on the arrival.The takeaway from this event:The TCAS did not operate as we would expect in time regarding a TA caution providing 40 seconds warning and an RA providing 25 seconds warning. It's hard to tell if the glider had just turned on its transponder or if the slow speed of the glider had an impact on our TCAS. The glider was in Class E airspace and outside the 30 mile equipment requirement (transponder) from the ORD Class B. What rules apply to gliders here; to me; is unknown to be honest.ATC had vectored us off the arrival and was assigning altitudes lower than published crossing restrictions by 1000 feet (5000 feet abeam STKNY).Vectors took us almost directly over a glider airpark with no warning about that on any chart we would ever use readily available. Some warning symbology or quick access information would assist considering the low altitudes we fly over these areas.In hindsight; I would have made clear to ATC we experienced a near mid air collision in that language as described in our FOM.




Synopsis: Captain reported a NMAC with a glider while on arrival.