B757 flight crew reports communications failure on both HF radios and both VHF radios during a flight over the western Atlantic to SMX. Communications are reestablished prior to landing using the observer's audio panel. A stuck mic was suggested by ATC.
Synopsis
B757 flight crew reports communications failure on both HF radios and both VHF radios during a flight over the western Atlantic to SMX. Communications are reestablished prior to landing using the observer's audio panel. A stuck mic was suggested by ATC.
Narrative
On several occasions; we were unable to transmit and receive on both Captain's and First Officer's HF audio panels during the class 2 navigation. It was intermittent during transmission of our position. Once we were within San Juan Center's airspace; we were unable to communicate on both VHF radios as well. On several occasions we would hear San Juan Center advising us of a stuck mike. We were unable to transmit on any of the forward radio panels. We tried to troubleshoot by unplugging both headsets and hand held mikes; but were unable to resolve or isolate problem. Several attempts were made on our end to isolate the problem with no success. Since we were unable to communicate with San Juan Center we elected to squawk 7600. At one point we were totally out of communication with San Juan Center for a period of 35 to 40 minutes. We had a deadheading First Officer that wanted to be in the cockpit for the landing. I asked him to try the mike on the observer's audio panel at which point we were finally successful in communicating with San Juan Center. At approximately 70 to 80 [NM] north of SXM; my First Officer was able to again communicate with ATC using #2 radio only. The landing was uneventful and both audio panels were written up upon landing. A follow up call was made to Dispatch and Maintenance.
Second reporter narrative
Southbound on L455; both HF radios became intermittently inoperative on Captain's and First Officer's side. Upon entering San Juan airspace we were able to communicate on VHF on both Captain and First Officer's side; but eventually communication became intermittent and then completely inoperative. While troubleshooting; we occasionally heard from ATC and other aircraft telling us that we might have a stuck mic. We disconnected all mics and headsets and systematically connected and tested each one with no success. About 100 DME north of SXM we squawked 7600. We called our deadheading First Officer to the cockpit and had him try using First Officer's hand mic on the observer's audio panel. This proved successful; so deadheading First Officer communicated with ATC until about 30 DME from SXM when for unknown reason; flying First Officer's radios began to operate normally again for remainder of flight to uneventful landing. We suspect the communication issue was with the radios and not the microphones.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.