|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||1201 To 1800|
|Locale Reference||atc facility : zab.artcc|
|Altitude||msl single value : 35000|
|Controlling Facilities||artcc : zab.artcc|
|Operator||common carrier : air carrier|
|Make Model Name||B757 Undifferentiated or Other Model|
|Operating Under FAR Part||Part 121|
|Navigation In Use||other|
|Flight Phase||cruise : level|
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Qualification||pilot : atp|
|Affiliation||company : air carrier|
|Function||flight crew : first officer|
|Anomaly||aircraft equipment problem : critical|
other anomaly other
|Independent Detector||aircraft equipment other aircraft equipment : vhf radios|
other flight crewa
|Resolutory Action||none taken : unable|
|Consequence||faa : reviewed incident with flight crew|
ATC Human Performance
|Primary Problem||ATC Facility|
|ATC Facility||communication equipment : zab.artcc|
procedure or policy : zab.artcc
A loud high-pitched tone was heard from both left and center VHF radios on abq center frequency 127.67. Center advised that this phenomenon occurs with certain B757 and airbus radios. The frequency was unmonitorable in the cockpit because the tone was continuous and loud. By clicking the microphone button, the tone stopped for about 10-15 seconds, then reoccurred. After leaving abq center airspace, the tone persisted any time the radios were tuned to 127.67, even on the ground at our destination (lax). This one renders the radios useless for monitoring due to the interference and distraction caused by the tone. The abq center seemed unconcerned about our predicament and refused to give us an alternate frequency. I was within a min or two of using the emergency frequency for monitoring purposes when the controller turned us over to another sector with a different frequency. I have flown the B757 through abq center for many yrs and have never heard of this problem. I recommend that abq center cease using frequency 127.67 until a solution is found. Callback conversation with reporter revealed the following information: reporter could not remember if the B757 had two or three digits after the decimal on their communication radio. The tone generated was sufficient to cause physical discomfort for both pilots. The flight crew was preparing to advise ZAB that they were forced to monitor guard frequency only. As they were processing for that decision, ZAB changed them to the next controller frequency. Reporter advised that his B757-200 did not have adjustable squelch control. Although the reporter has been in, out and through abq recently, he has not been assigned that specific aircraft. The model B757's he subsequently used did not incur that same tone problem when using that frequency.
Original NASA ASRS Text
Title: B757-200 FLT CREW INCURS ZAB 127.67 FREQ INTERFERENCE TO THE LEVEL THAT ATC COM BECOMES UNUSABLE. FREQ CHANGE TO NEXT SECTOR RESOLVES IMMEDIATE PROB, BUT TONE STILL AUDIBLE ON THE GND AT LAX ARPT.
Narrative: A LOUD HIGH-PITCHED TONE WAS HEARD FROM BOTH LEFT AND CENTER VHF RADIOS ON ABQ CENTER FREQ 127.67. CENTER ADVISED THAT THIS PHENOMENON OCCURS WITH CERTAIN B757 AND AIRBUS RADIOS. THE FREQ WAS UNMONITORABLE IN THE COCKPIT BECAUSE THE TONE WAS CONTINUOUS AND LOUD. BY CLICKING THE MICROPHONE BUTTON, THE TONE STOPPED FOR ABOUT 10-15 SECS, THEN REOCCURRED. AFTER LEAVING ABQ CENTER AIRSPACE, THE TONE PERSISTED ANY TIME THE RADIOS WERE TUNED TO 127.67, EVEN ON THE GND AT OUR DESTINATION (LAX). THIS ONE RENDERS THE RADIOS USELESS FOR MONITORING DUE TO THE INTERFERENCE AND DISTRACTION CAUSED BY THE TONE. THE ABQ CENTER SEEMED UNCONCERNED ABOUT OUR PREDICAMENT AND REFUSED TO GIVE US AN ALTERNATE FREQ. I WAS WITHIN A MIN OR TWO OF USING THE EMER FREQ FOR MONITORING PURPOSES WHEN THE CTLR TURNED US OVER TO ANOTHER SECTOR WITH A DIFFERENT FREQ. I HAVE FLOWN THE B757 THROUGH ABQ CENTER FOR MANY YRS AND HAVE NEVER HEARD OF THIS PROB. I RECOMMEND THAT ABQ CENTER CEASE USING FREQ 127.67 UNTIL A SOLUTION IS FOUND. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR COULD NOT REMEMBER IF THE B757 HAD TWO OR THREE DIGITS AFTER THE DECIMAL ON THEIR COM RADIO. THE TONE GENERATED WAS SUFFICIENT TO CAUSE PHYSICAL DISCOMFORT FOR BOTH PLTS. THE FLT CREW WAS PREPARING TO ADVISE ZAB THAT THEY WERE FORCED TO MONITOR GUARD FREQ ONLY. AS THEY WERE PROCESSING FOR THAT DECISION, ZAB CHANGED THEM TO THE NEXT CTLR FREQ. RPTR ADVISED THAT HIS B757-200 DID NOT HAVE ADJUSTABLE SQUELCH CTL. ALTHOUGH THE RPTR HAS BEEN IN, OUT AND THROUGH ABQ RECENTLY, HE HAS NOT BEEN ASSIGNED THAT SPECIFIC ACFT. THE MODEL B757'S HE SUBSEQUENTLY USED DID NOT INCUR THAT SAME TONE PROB WHEN USING THAT FREQ.
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.