Citationjet (C525/C526) - CJ I / II / III / IV
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 2
Time Pressure; Confusion; Workload; Communication Breakdown; Situational Awareness; Human-Machine Interface; Distraction
ATC Issue All Types; Airspace Violation All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance
Procedure
Chicago Executive Airport has an instrument approach to only one runway (RWY 16). So; when the winds are favoring runway 34; aircraft are asked to cancel their IFR prior to circling because of our proximity to ORD airport. If the field is IFR; C90 needs to protect for the circle with O'Hare's traffic. When I began working the Local Control position; winds were gusting out of the northeast at over 20 knots and aircraft were canceling IFR and circling to runway 34 with a ceiling of BKN011. An EA50 reported the cloud bases at 1;500 MSL. Our field elevation is 646 AGL. The one-minute ASOS observation indicated BKN009. The C90 North Satellite sector was informed that the field was IFR with a ceiling of BKN009. A SPECI transmitted indicating 01014G22KT 10SM BKN009.Aircraft X called on the RNAV RWY 16 approach. He was instructed to circle west for left traffic for runway 34. Aircraft Y called on the RNAV RWY 16 approach approximately 6 miles in trail of Aircraft X who had just begun his circle. Realizing standard separation would ultimately be lost if the scenario continued; I called C90 to ask for missed approach instructions for Aircraft Y. C90 gave me a 040-heading. While issuing the missed approach to Aircraft Y; C90 called on the shout line asking if Aircraft X failed to cancel his IFR. I reiterated to C90 that the field was IFR and canceling was not an option.When the weather is VFR and aircraft are canceling IFR prior to circling to runway 34; the aircraft either squawk VFR or controllers put the letter 'V' in the special designator area of the data block to signal to C90 that the aircraft is; indeed; now VFR. Neither of those things were happening since I called C90 to inform them of the field being IFR.  The Standard Operating Procedures at PWK require controllers to inform C90 when the field goes from VFR to IFR and vice versa. I would recommend that when we are doing this (while advertising the circle to runway 34) that we reiterate to C90;  'Field is IFR. You need to protect for the circle to runway 34.' or 'Field is VFR. Returning to canceling IFR for the circle to runway 34.'
PWK Controller reported an IFR aircraft that was thought to be VFR due to a procedure usually used in VFR conditions.