Narrative:

Aircraft was tracking direct to cgt VOR. Center assigned heading somewhat north of track 'vector to cgt.' had previously received other vectors and airspeed changes for arrival traffic into O'hare. Vector acknowledged by captain, first officer was flying. Radio shortly became too quiet. Also vector was taking aircraft well north of course. Numerous attempts on both VHF radios, from both cockpit positions on current frequency. Frequency relieved from dispatch via ACARS, lost frequency. Did not establish contact. Checked and rechked for stuck microphone. Also tried both VHF receivers on O'hare tower and approach control and 121.5 from both cockpit positions with no results. Aircraft was already squawking 7600 and we knew center was aware of lost contact by first and additional message over ACARS from dispatch, 'center advises stuck microphone.' rechked--no stuck microphone. Present assigned vector was taking aircraft out over lake michigan. Decision was made to turn direct cgt VOR and commence descent, squawking 7700 to advise center of change of heading and descent for landing at O'hare. Visibility was 50 mi plus. Ord was in sight. Had already prior to problem received ord ATIS and planned for approach and landing. Briefed for specially vigilant traffic watch. Still could not accept a double VHF communication failure and besides #1 VHF was operational on ACARS. Selected ATIS once again to try again to pick up a continuous broadcast. Received ATIS. Still unable to transmit and receive on center frequency. Decided to disconnect all mics and headphones, and try one at a time from one cockpit position only. Both pilots had been using the combination headset-lip mics. As soon as both these were completely disconnected, received center on #2 VHF cockpit speakers. Advised center and asked for instructions in event of further failure, and single frequency approach or minimum frequency changes. Excellent handling and handoff to approach. Approach also gave landing clearance on approach frequency. Aircraft landed normally. De-briefed center on ground. They advise center was hearing our xmissions. They did not indicate hearing either pilot cockpit conversation which would have happened with stuck microphone. Maintenance changed both communication selector boxes. No further problems.

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Original NASA ASRS Text

Title: ACR WDB EQUIPMENT MALFUNCTION CAUSES LOSS OF RADIO COM. COM EMERGENCY DECLARED.

Narrative: ACFT WAS TRACKING DIRECT TO CGT VOR. CENTER ASSIGNED HDG SOMEWHAT N OF TRACK 'VECTOR TO CGT.' HAD PREVIOUSLY RECEIVED OTHER VECTORS AND AIRSPD CHANGES FOR ARR TFC INTO O'HARE. VECTOR ACKNOWLEDGED BY CAPT, F/O WAS FLYING. RADIO SHORTLY BECAME TOO QUIET. ALSO VECTOR WAS TAKING ACFT WELL N OF COURSE. NUMEROUS ATTEMPTS ON BOTH VHF RADIOS, FROM BOTH COCKPIT POSITIONS ON CURRENT FREQ. FREQ RELIEVED FROM DISPATCH VIA ACARS, LOST FREQ. DID NOT ESTABLISH CONTACT. CHKED AND RECHKED FOR STUCK MIC. ALSO TRIED BOTH VHF RECEIVERS ON O'HARE TWR AND APCH CTL AND 121.5 FROM BOTH COCKPIT POSITIONS WITH NO RESULTS. ACFT WAS ALREADY SQUAWKING 7600 AND WE KNEW CENTER WAS AWARE OF LOST CONTACT BY FIRST AND ADDITIONAL MESSAGE OVER ACARS FROM DISPATCH, 'CENTER ADVISES STUCK MIC.' RECHKED--NO STUCK MIC. PRESENT ASSIGNED VECTOR WAS TAKING ACFT OUT OVER LAKE MICHIGAN. DECISION WAS MADE TO TURN DIRECT CGT VOR AND COMMENCE DSCNT, SQUAWKING 7700 TO ADVISE CENTER OF CHANGE OF HDG AND DSCNT FOR LNDG AT O'HARE. VISIBILITY WAS 50 MI PLUS. ORD WAS IN SIGHT. HAD ALREADY PRIOR TO PROB RECEIVED ORD ATIS AND PLANNED FOR APCH AND LNDG. BRIEFED FOR SPECIALLY VIGILANT TFC WATCH. STILL COULD NOT ACCEPT A DOUBLE VHF COM FAILURE AND BESIDES #1 VHF WAS OPERATIONAL ON ACARS. SELECTED ATIS ONCE AGAIN TO TRY AGAIN TO PICK UP A CONTINUOUS BROADCAST. RECEIVED ATIS. STILL UNABLE TO XMIT AND RECEIVE ON CENTER FREQ. DECIDED TO DISCONNECT ALL MICS AND HEADPHONES, AND TRY ONE AT A TIME FROM ONE COCKPIT POS ONLY. BOTH PLTS HAD BEEN USING THE COMBINATION HEADSET-LIP MICS. AS SOON AS BOTH THESE WERE COMPLETELY DISCONNECTED, RECEIVED CENTER ON #2 VHF COCKPIT SPEAKERS. ADVISED CENTER AND ASKED FOR INSTRUCTIONS IN EVENT OF FURTHER FAILURE, AND SINGLE FREQ APCH OR MINIMUM FREQ CHANGES. EXCELLENT HANDLING AND HDOF TO APCH. APCH ALSO GAVE LNDG CLRNC ON APCH FREQ. ACFT LANDED NORMALLY. DE-BRIEFED CENTER ON GND. THEY ADVISE CENTER WAS HEARING OUR XMISSIONS. THEY DID NOT INDICATE HEARING EITHER PLT COCKPIT CONVERSATION WHICH WOULD HAVE HAPPENED WITH STUCK MIC. MAINT CHANGED BOTH COM SELECTOR BOXES. NO FURTHER PROBS.

Data retrieved from NASA's ASRS site as of August 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.