Narrative:

I was assigned to relieve the local controller/controller in charge at XA00. After doing so; I then learned that the relief briefing was missing some key details when C90 approach controller called and asked if I was providing separation from those 2 aircraft; referring to a departure outbound on a 030 degree heading; aircraft X and aircraft Y on a 160 degree heading. I replied yes; believing that we were in contact by radio; and that control instructions could be issued; only to find neither aircraft was on our frequency. Their track appeared that they would progress to a crossing vector; which could result in less than standard separation. Upon hearing the question; the relieved controller stated that he meant to get the inbound to cancel IFR. That's when I learned that something in the briefing was missing. I called each aircraft with no response from them. All I could do was watch as they passed. Fortunately; they passed with vertical separation and lateral separation hard to judge; but no conflict alert went off. No corrective action on my part could be taken because both aircraft were on C90 frequencys at arrival and departure.

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Original NASA ASRS Text

Title: PWK LCL CTLR NEARLY HAS AN ERROR WHEN INCOMPLETE POS RELIEF BRIEFING LEADS TO FALSE ASSUMPTION ABOUT COMS.

Narrative: I WAS ASSIGNED TO RELIEVE THE LCL CTLR/CIC AT XA00. AFTER DOING SO; I THEN LEARNED THAT THE RELIEF BRIEFING WAS MISSING SOME KEY DETAILS WHEN C90 APCH CTLR CALLED AND ASKED IF I WAS PROVIDING SEPARATION FROM THOSE 2 ACFT; REFERRING TO A DEP OUTBOUND ON A 030 DEG HDG; ACFT X AND ACFT Y ON A 160 DEG HDG. I REPLIED YES; BELIEVING THAT WE WERE IN CONTACT BY RADIO; AND THAT CTL INSTRUCTIONS COULD BE ISSUED; ONLY TO FIND NEITHER ACFT WAS ON OUR FREQ. THEIR TRACK APPEARED THAT THEY WOULD PROGRESS TO A XING VECTOR; WHICH COULD RESULT IN LTSS. UPON HEARING THE QUESTION; THE RELIEVED CTLR STATED THAT HE MEANT TO GET THE INBOUND TO CANCEL IFR. THAT'S WHEN I LEARNED THAT SOMETHING IN THE BRIEFING WAS MISSING. I CALLED EACH ACFT WITH NO RESPONSE FROM THEM. ALL I COULD DO WAS WATCH AS THEY PASSED. FORTUNATELY; THEY PASSED WITH VERT SEPARATION AND LATERAL SEPARATION HARD TO JUDGE; BUT NO CONFLICT ALERT WENT OFF. NO CORRECTIVE ACTION ON MY PART COULD BE TAKEN BECAUSE BOTH ACFT WERE ON C90 FREQS AT ARR AND DEP.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.