Narrative:

After being cleared for the runway 28 profile descent into sfo the frequency got very quiet, so we called ZOA for a radio check. We were unable to raise them on any frequency on either radio (VHF 1 or 2), although we had good sidetone between each other. We finally reestablished radio contact with bay approach on the frequency listed on the approach chart. We made 2 more frequency changes with approach control and were inside menlo descending to 6000' when I called them for further clearance, as we had not been cleared for an approach to either runway. (First officer was flying the aircraft as his initial cord had separated from the jack after takeoff from lax.) we leveled at 6000' and flew inbound on the localizer while we tried to reestablish radio contact with anyone and remain VFR with the field in sight. The first officer had, by this time, plugged the hand microphone into his console and we both transmitted using both radios (at different times) on bay approach, sfo tower, sfo ground and ramp control. We flew over the airport at 6000' squawking 7600 on the IFF, and entered a left downwind in order to keep the field in sight. While on the downwind leg at 6000' we established radio contact with sfo ground control and they cleared us to land on runway 28L which we did. While on downwind, the first officer and I discussed our options. We considered getting out the fom and reviewing the emergency section to see if we were missing anything. We decided that 6000' with the traffic at sfo was not the place to be digging in the book. We also decided that west/O landing clearance, visually or aurally, we would rock the wings on final and continue to land. After shutting down the aircraft and completing the checklist we discovered that both radios were working normally on all frequencys. Ground control asked me to contact by approach on the phone, which I did. I spoke to area manager of bay TRACON and explained what had happened. His only criticism was that we did not listen on the sfo VOR for voice xmissions. We continued back to lax on another plane and surfaced to ont where I talked to the chicago dispatch duty manager and again explained the problem. Callback conversation with reporter revealed the following: the company never could duplicate the problem, but they did change both transceivers as a precaution. During flight crew/ATC review the controllers said it sounded like a stuck microphone. Further analysis indicates perhaps the first officer's boom microphone cord sep leaving lax was causing a problem, then when it was disconnected at the ramp the problem went away.

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Original NASA ASRS Text

Title: ACR MLG LOST RADIO COM WITH ZOA, OAK TRACON AND SFO TWR WHILE FLYING A PROFILE DESCENT INTO SFO. MADE A VISUAL CIRCLE FROM OVER THE ARPT AND WAS ABLE TO REESTABLISH CONTACT WITH SFO GND CTL BEFORE LNDG. AFTER LNDG RADIO PROBLEM COULD NOT BE DUPLICATED.

Narrative: AFTER BEING CLRED FOR THE RWY 28 PROFILE DSNT INTO SFO THE FREQ GOT VERY QUIET, SO WE CALLED ZOA FOR A RADIO CHK. WE WERE UNABLE TO RAISE THEM ON ANY FREQ ON EITHER RADIO (VHF 1 OR 2), ALTHOUGH WE HAD GOOD SIDETONE BTWN EACH OTHER. WE FINALLY REESTABLISHED RADIO CONTACT WITH BAY APCH ON THE FREQ LISTED ON THE APCH CHART. WE MADE 2 MORE FREQ CHANGES WITH APCH CTL AND WERE INSIDE MENLO DSNDING TO 6000' WHEN I CALLED THEM FOR FURTHER CLRNC, AS WE HAD NOT BEEN CLRED FOR AN APCH TO EITHER RWY. (F/O WAS FLYING THE ACFT AS HIS INITIAL CORD HAD SEPARATED FROM THE JACK AFTER TKOF FROM LAX.) WE LEVELED AT 6000' AND FLEW INBND ON THE LOC WHILE WE TRIED TO REESTABLISH RADIO CONTACT WITH ANYONE AND REMAIN VFR WITH THE FIELD IN SIGHT. THE F/O HAD, BY THIS TIME, PLUGGED THE HAND MIC INTO HIS CONSOLE AND WE BOTH XMITTED USING BOTH RADIOS (AT DIFFERENT TIMES) ON BAY APCH, SFO TWR, SFO GND AND RAMP CTL. WE FLEW OVER THE ARPT AT 6000' SQUAWKING 7600 ON THE IFF, AND ENTERED A LEFT DOWNWIND IN ORDER TO KEEP THE FIELD IN SIGHT. WHILE ON THE DOWNWIND LEG AT 6000' WE ESTABLISHED RADIO CONTACT WITH SFO GND CTL AND THEY CLRED US TO LAND ON RWY 28L WHICH WE DID. WHILE ON DOWNWIND, THE F/O AND I DISCUSSED OUR OPTIONS. WE CONSIDERED GETTING OUT THE FOM AND REVIEWING THE EMER SECTION TO SEE IF WE WERE MISSING ANYTHING. WE DECIDED THAT 6000' WITH THE TFC AT SFO WAS NOT THE PLACE TO BE DIGGING IN THE BOOK. WE ALSO DECIDED THAT W/O LNDG CLRNC, VISUALLY OR AURALLY, WE WOULD ROCK THE WINGS ON FINAL AND CONTINUE TO LAND. AFTER SHUTTING DOWN THE ACFT AND COMPLETING THE CHKLIST WE DISCOVERED THAT BOTH RADIOS WERE WORKING NORMALLY ON ALL FREQS. GND CTL ASKED ME TO CONTACT BY APCH ON THE PHONE, WHICH I DID. I SPOKE TO AREA MGR OF BAY TRACON AND EXPLAINED WHAT HAD HAPPENED. HIS ONLY CRITICISM WAS THAT WE DID NOT LISTEN ON THE SFO VOR FOR VOICE XMISSIONS. WE CONTINUED BACK TO LAX ON ANOTHER PLANE AND SURFACED TO ONT WHERE I TALKED TO THE CHICAGO DISPATCH DUTY MGR AND AGAIN EXPLAINED THE PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: THE COMPANY NEVER COULD DUPLICATE THE PROB, BUT THEY DID CHANGE BOTH TRANSCEIVERS AS A PRECAUTION. DURING FLT CREW/ATC REVIEW THE CTLRS SAID IT SOUNDED LIKE A STUCK MIC. FURTHER ANALYSIS INDICATES PERHAPS THE F/O'S BOOM MIC CORD SEP LEAVING LAX WAS CAUSING A PROB, THEN WHEN IT WAS DISCONNECTED AT THE RAMP THE PROB WENT AWAY.

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.