Narrative:

I was working west arrival runway 28 and we were doing simultaneous ILS approaches along runway 27L. The aircraft was about a 15 mile final at 5;000 about to descend on the approach. Aircraft X was turning base to final on 27L and went through the final right below aircraft Y who was on a 15 mile final for runway 28. The monitor tried to cancel the approach clearance on aircraft Y but he was not on the monitor frequency. I told aircraft Y to monitor the tower 120.75 and report willt the FAF. The pilot read back call the tower at willt 120.75. I missed the read back and he never took the frequency change and he was still on my frequency. One thing about simultaneous ILS approaches at ord is the arrival controller will tell the pilot to monitor the tower and report the FAF prior to 16 mile final. There is no way the monitor knows if the pilot took that frequency change or went to the wrong frequency because they never check in with anyone when they switch over to monitor the tower frequency. The monitor; monitors the tower frequency and has override capability. So if something needs to be done; they keep up over the tower controller and fix it. As in my case; the pilot read back the wrong instructions and was not able to take the corrective action from the monitor. Something could go very very wrong if an aircraft goes through the final or drifts off the final into the other one and the monitor can't do anything about it if the pilot isn't on that frequency. I think the pilot should check in as soon as he is on the tower frequency so the monitor knows he is there. This does make the tower make more transmissions; but it's safer. Or have a separate monitor frequency; and then have the monitor switch the aircraft to the tower at the FAF.

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Original NASA ASRS Text

Title: C90 Controller described a conflict event when traffic being vectored for simultaneous approach procedures crossed the final approach course; the reporter offering a number of suggestions for procedural changes.

Narrative: I was working West arrival Runway 28 and we were doing simultaneous ILS approaches along Runway 27L. The aircraft was about a 15 mile final at 5;000 about to descend on the approach. Aircraft X was turning base to final on 27L and went through the final right below Aircraft Y who was on a 15 mile final for Runway 28. The monitor tried to cancel the approach clearance on Aircraft Y but he was not on the monitor frequency. I told Aircraft Y to monitor the Tower 120.75 and report WILLT the FAF. The pilot read back call the Tower at WILLT 120.75. I missed the read back and he never took the frequency change and he was still on my frequency. One thing about simultaneous ILS approaches at ORD is the Arrival Controller will tell the pilot to monitor the Tower and report the FAF prior to 16 mile final. There is no way the monitor knows if the pilot took that frequency change or went to the wrong frequency because they never check in with anyone when they switch over to monitor the Tower frequency. The Monitor; monitors the Tower frequency and has override capability. So if something needs to be done; they keep up over the Tower Controller and fix it. As in my case; the pilot read back the wrong instructions and was not able to take the corrective action from the monitor. Something could go very very wrong if an aircraft goes through the final or drifts off the final into the other one and the monitor can't do anything about it if the pilot isn't on that frequency. I think the pilot should check in as soon as he is on the Tower frequency so the monitor knows he is there. This does make the Tower make more transmissions; but it's safer. Or have a separate monitor frequency; and then have the monitor switch the aircraft to the Tower at the FAF.

Data retrieved from NASA's ASRS site as of April 2012 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.