Communication Breakdown; Human-Machine Interface; Troubleshooting
ATC Issue All Types; Aircraft Equipment Problem Critical
Aircraft Equipment Problem Dissipated; Flight Crew Returned To Departure Airport; General Declared Emergency; General Maintenance Action
Aircraft
All communications were normal from the gate through departure. On climb out we did not receive a call from Tower to switch to Departure Control. After several attempts to contact Tower we switched to Departure Control. When we were unable to contact Departure Control we tried several frequencies and were unable to establish communication. 7600 was selected on the transponder and we leveled at the last assigned altitude of 5;000 FT. For some time we tried to resolve the problem by disconnecting all microphones and headsets including those at the observer seats. Both communication radios and both audio select panels were tested. As a last resort we sent an ACARS message to Dispatch advising him of our status and requesting him to contact ATC and advise that we were returning to our departure airport. On base leg we heard a transmission from Tower. At that point both VHF communications radios became fully operational and remained so throughout the landing. Maintenance was unable to duplicate the problem at the gate and all communication functions remained normal.
When they were unable to communicate with ATC after takeoff the flight crew of a B757-200 squawked 7600 and sent an ACARS message to Dispatch requesting them to advise ATC at their departure airport they would be returning. On base leg communications were re-established. No cause for the loss and/or its resurrection was determined by Maintenance.