Narrative:

First noticed that boom microphone was hot. Disconnected my headset plugs from socket and attempted communication with atl departure on hand-held microphone. No evidence of transmission or reception on either VHF 1 or VHF 2 could be determined. Copilot reinserted headset plugs into socket to check audio through earpiece. No audio could be detected. Captain squawked code 7600 and we decided to return to atl in VFR conditions. Turned to heading 270 degrees (previously northbound on vector). With speaker vol and VHF 1 radio vol on maximum, communication (1 X 5) reestablished on captain's speaker only. I took over flying the aircraft while captain handled the communications, as the vol was too weak for me to hear. After uneventful visibility approach into atl, maintenance found copilot's yoke push-to-talk switched failed in the transmit position. This medium large transport model aircraft is 1 of 3 aircraft in the fleet which has minimum autoplt, instrumentation and communication equipment. Apparently with a microphone keyed in this aircraft, both speakers are muted. Although both pilots were wearing earpieces at the time, incoming audio must have also been muted due to the failure of the push-to-talk switch. Modification to rectify the problem of speaker muting while transmitting was in progress. It is unknown whether this aircraft had the modification.

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Original NASA ASRS Text

Title: FLT CREW OF ACR MLG DISCOVERED RADIO COM PROBLEM ON DEP FROM ATL. RETURN LAND.

Narrative: FIRST NOTICED THAT BOOM MIC WAS HOT. DISCONNECTED MY HEADSET PLUGS FROM SOCKET AND ATTEMPTED COM WITH ATL DEP ON HAND-HELD MIC. NO EVIDENCE OF XMISSION OR RECEPTION ON EITHER VHF 1 OR VHF 2 COULD BE DETERMINED. COPLT REINSERTED HEADSET PLUGS INTO SOCKET TO CHK AUDIO THROUGH EARPIECE. NO AUDIO COULD BE DETECTED. CAPT SQUAWKED CODE 7600 AND WE DECIDED TO RETURN TO ATL IN VFR CONDITIONS. TURNED TO HDG 270 DEGS (PREVIOUSLY NBOUND ON VECTOR). WITH SPEAKER VOL AND VHF 1 RADIO VOL ON MAX, COM (1 X 5) REESTABLISHED ON CAPT'S SPEAKER ONLY. I TOOK OVER FLYING THE ACFT WHILE CAPT HANDLED THE COMS, AS THE VOL WAS TOO WEAK FOR ME TO HEAR. AFTER UNEVENTFUL VIS APCH INTO ATL, MAINT FOUND COPLT'S YOKE PUSH-TO-TALK SWITCHED FAILED IN THE XMIT POS. THIS MLG MODEL ACFT IS 1 OF 3 ACFT IN THE FLEET WHICH HAS MINIMUM AUTOPLT, INSTRUMENTATION AND COM EQUIP. APPARENTLY WITH A MIC KEYED IN THIS ACFT, BOTH SPEAKERS ARE MUTED. ALTHOUGH BOTH PLTS WERE WEARING EARPIECES AT THE TIME, INCOMING AUDIO MUST HAVE ALSO BEEN MUTED DUE TO THE FAILURE OF THE PUSH-TO-TALK SWITCH. MODIFICATION TO RECTIFY THE PROB OF SPEAKER MUTING WHILE XMITTING WAS IN PROGRESS. IT IS UNKNOWN WHETHER THIS ACFT HAD THE MODIFICATION.

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.