Narrative:

ATC facility: ord approach, ILS runway 22R. We were cleared for approach about 15 mi out and told to call the tower over ridge. Apparently, while inserting tower frequency, first officer accidentally moved approach control frequency also. Approach tried to contact us to slow us due to 1 aircraft ahead. We were unaware of any aircraft ahead of us. First officer switched frequencys just outside ridge and heard tower calling. Tower cleared us to land and once on the taxi asked us to call approach on the telephone. We were unaware of any problem prior to this. We called and apologized about the error. We both thought it was just a quiet sunday morning at ord. If we had known there was traffic ahead I probably would have been more diligent in listening up and may have caught the inadvertent frequency shift. TCASII showed the only aircraft about 3 mi ahead which seemed normal at the time. ATC told us they pulled an aircraft out of the pattern due to no communication with us. I will just have to be more aware in the future when frequency changes occur.

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Original NASA ASRS Text

Title: LOSS OF COM FREQ ON APCH TO ORD RWY 22R ILS. FO INADVERTENTLY KNOCKED APCH CTL FREQ OFF WHEN SETTING UP FOR XFER TO TWR FREQ. ATC, UPSET AND CONCERNED WITH SEPARATION WITH ACFT IN FRONT OF ACR X, SENT ACR Y AROUND.

Narrative: ATC FACILITY: ORD APCH, ILS RWY 22R. WE WERE CLRED FOR APCH ABOUT 15 MI OUT AND TOLD TO CALL THE TWR OVER RIDGE. APPARENTLY, WHILE INSERTING TWR FREQ, FO ACCIDENTALLY MOVED APCH CTL FREQ ALSO. APCH TRIED TO CONTACT US TO SLOW US DUE TO 1 ACFT AHEAD. WE WERE UNAWARE OF ANY ACFT AHEAD OF US. FO SWITCHED FREQS JUST OUTSIDE RIDGE AND HEARD TWR CALLING. TWR CLRED US TO LAND AND ONCE ON THE TAXI ASKED US TO CALL APCH ON THE TELEPHONE. WE WERE UNAWARE OF ANY PROB PRIOR TO THIS. WE CALLED AND APOLOGIZED ABOUT THE ERROR. WE BOTH THOUGHT IT WAS JUST A QUIET SUNDAY MORNING AT ORD. IF WE HAD KNOWN THERE WAS TFC AHEAD I PROBABLY WOULD HAVE BEEN MORE DILIGENT IN LISTENING UP AND MAY HAVE CAUGHT THE INADVERTENT FREQ SHIFT. TCASII SHOWED THE ONLY ACFT ABOUT 3 MI AHEAD WHICH SEEMED NORMAL AT THE TIME. ATC TOLD US THEY PULLED AN ACFT OUT OF THE PATTERN DUE TO NO COM WITH US. I WILL JUST HAVE TO BE MORE AWARE IN THE FUTURE WHEN FREQ CHANGES OCCUR.

Data retrieved from NASA's ASRS site as of July 2007 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.