Narrative:

Air carrier X and cga Y were on assigned headings for northbound traffic, all at FL370. Clearing northbound traffic, cga Y was issued an additional vector for air carrier X. No response was received from cga Y and clearance was reissued on primary, standby, and backup (buec) transmitters, all with no response. Air carrier X was issued a descent clearance to FL350 but no acknowledgement was received. Again clearance was reissued on primaries, standby, and backup transmitters with no response. Supervisor was notified and attempts were made to contact the aircraft from the instructor override jack, data position, and overhead position with no success. During this period, aircraft were reporting on our frequency (128.77, ffo super high) indicating they were getting either no response or a totally unreadable response and were returning to their previous frequency. We attempted to have boundary sector relay control instructions to the aircraft, but contact could not be reestablished prior to the aircraft passing in close proximity to each other. Neither reported evasive action or sighting the other aircraft. The sector was combined at day high sector. At XB10 local 128.77 returned to service without other action. The airway facility sector at ZID states they have no explanation for the failure and could find no mechanical explanation. On the tapes after XA55, no record of radio xmissions from the ffo positions can be heard, however, the aircraft and all landline communications can be heard. We were informed that maintenance had been working on a 'crosstalk' problem between our frequency 128.77 and wab super high frequency 132.77, and the controllers at wab indicate that the 'crosstalk' problem vanished at approximately the same time we lost our frequencys. Additionally, at XE00 local all transmitters at the ffo super high failed again and an operational error was narrowly avoided when the failure was discovered while another controller was still talking to one of the aircraft.

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Original NASA ASRS Text

Title: RADIO TRANSMITTER FAILURE AT FAC RESULTED IN LESS THAN STANDARD SEPARATION BETWEEN 2 ACFT.

Narrative: ACR X AND CGA Y WERE ON ASSIGNED HDGS FOR NBOUND TFC, ALL AT FL370. CLEARING NBOUND TFC, CGA Y WAS ISSUED AN ADDITIONAL VECTOR FOR ACR X. NO RESPONSE WAS RECEIVED FROM CGA Y AND CLRNC WAS REISSUED ON PRIMARY, STANDBY, AND BACKUP (BUEC) XMITTERS, ALL WITH NO RESPONSE. ACR X WAS ISSUED A DSCNT CLRNC TO FL350 BUT NO ACKNOWLEDGEMENT WAS RECEIVED. AGAIN CLRNC WAS REISSUED ON PRIMARIES, STANDBY, AND BACKUP XMITTERS WITH NO RESPONSE. SUPVR WAS NOTIFIED AND ATTEMPTS WERE MADE TO CONTACT THE ACFT FROM THE INSTRUCTOR OVERRIDE JACK, DATA POSITION, AND OVERHEAD POSITION WITH NO SUCCESS. DURING THIS PERIOD, ACFT WERE REPORTING ON OUR FREQ (128.77, FFO SUPER HIGH) INDICATING THEY WERE GETTING EITHER NO RESPONSE OR A TOTALLY UNREADABLE RESPONSE AND WERE RETURNING TO THEIR PREVIOUS FREQ. WE ATTEMPTED TO HAVE BOUNDARY SECTOR RELAY CONTROL INSTRUCTIONS TO THE ACFT, BUT CONTACT COULD NOT BE REESTABLISHED PRIOR TO THE ACFT PASSING IN CLOSE PROX TO EACH OTHER. NEITHER REPORTED EVASIVE ACTION OR SIGHTING THE OTHER ACFT. THE SECTOR WAS COMBINED AT DAY HIGH SECTOR. AT XB10 LCL 128.77 RETURNED TO SERVICE WITHOUT OTHER ACTION. THE AIRWAY FAC SECTOR AT ZID STATES THEY HAVE NO EXPLANATION FOR THE FAILURE AND COULD FIND NO MECHANICAL EXPLANATION. ON THE TAPES AFTER XA55, NO RECORD OF RADIO XMISSIONS FROM THE FFO POSITIONS CAN BE HEARD, HOWEVER, THE ACFT AND ALL LANDLINE COMS CAN BE HEARD. WE WERE INFORMED THAT MAINT HAD BEEN WORKING ON A 'CROSSTALK' PROBLEM BETWEEN OUR FREQ 128.77 AND WAB SUPER HIGH FREQ 132.77, AND THE CTLRS AT WAB INDICATE THAT THE 'CROSSTALK' PROBLEM VANISHED AT APPROX THE SAME TIME WE LOST OUR FREQS. ADDITIONALLY, AT XE00 LCL ALL XMITTERS AT THE FFO SUPER HIGH FAILED AGAIN AND AN OPERATIONAL ERROR WAS NARROWLY AVOIDED WHEN THE FAILURE WAS DISCOVERED WHILE ANOTHER CTLR WAS STILL TALKING TO ONE OF THE ACFT.

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.