Narrative:

Medium large transport X was level at FL330 and given clearance to descend and maintain FL240 and told to start the descent now, medium large transport Y was level at FL310 requesting FL350 was climbed to FL330. Medium large transport Y was climbing at a very good rate of climb since his pit departure. The aircraft were 40 mi apart at the time of the clrncs. Medium large transport X was not descending at a normal rate of descent (only 400' in over a minute after reporting leaving FL330). Controller tried to expedite his descent but the frequency went dead. I tried to key the microphone a few times and played with the headset jack to see if the transmitter lights would come on. It was obvious that nothing was transmitting. The frequencys did come back when the aircraft were about 12 mi apart and controller tired to push him down and get a report out of FL310 (medium large transport Y had been level at FL330 long before), but it was too late. Had the frequency not failed, there is no question that standard sep could have been maintained. The relieving controller also had problems with that frequency and it was logged out to be repaired. Controller used judgement technique of initial clrncs taught by training departure at center. Callback conversation with reporter revealed the following: reporter was about to be relieved and tracker and other controller had plugged in about the time of the incident. Aircraft were approximately 1600' and 3 mi at closest point. Traffic vol was light to moderate. No traffic advisories were given prior to or after incident, but aircraft did report seeing each other. Reporter says same thing happened to radio about 10 days later, could be a jack problem.

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Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN CLIMBING AND DESCENDING MLG ACFT, ATC RADIO COM PROBLEM AND CTLR TECHNIQUE.

Narrative: MLG X WAS LEVEL AT FL330 AND GIVEN CLRNC TO DSND AND MAINTAIN FL240 AND TOLD TO START THE DSCNT NOW, MLG Y WAS LEVEL AT FL310 REQUESTING FL350 WAS CLBED TO FL330. MLG Y WAS CLBING AT A VERY GOOD RATE OF CLB SINCE HIS PIT DEP. THE ACFT WERE 40 MI APART AT THE TIME OF THE CLRNCS. MLG X WAS NOT DSNDING AT A NORMAL RATE OF DSCNT (ONLY 400' IN OVER A MINUTE AFTER RPTING LEAVING FL330). CTLR TRIED TO EXPEDITE HIS DSCNT BUT THE FREQ WENT DEAD. I TRIED TO KEY THE MIC A FEW TIMES AND PLAYED WITH THE HEADSET JACK TO SEE IF THE XMITTER LIGHTS WOULD COME ON. IT WAS OBVIOUS THAT NOTHING WAS XMITTING. THE FREQS DID COME BACK WHEN THE ACFT WERE ABOUT 12 MI APART AND CTLR TIRED TO PUSH HIM DOWN AND GET A RPT OUT OF FL310 (MLG Y HAD BEEN LEVEL AT FL330 LONG BEFORE), BUT IT WAS TOO LATE. HAD THE FREQ NOT FAILED, THERE IS NO QUESTION THAT STANDARD SEP COULD HAVE BEEN MAINTAINED. THE RELIEVING CTLR ALSO HAD PROBS WITH THAT FREQ AND IT WAS LOGGED OUT TO BE REPAIRED. CTLR USED JUDGEMENT TECHNIQUE OF INITIAL CLRNCS TAUGHT BY TRNING DEP AT CENTER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR WAS ABOUT TO BE RELIEVED AND TRACKER AND OTHER CTLR HAD PLUGGED IN ABOUT THE TIME OF THE INCIDENT. ACFT WERE APPROX 1600' AND 3 MI AT CLOSEST POINT. TFC VOL WAS LIGHT TO MODERATE. NO TFC ADVISORIES WERE GIVEN PRIOR TO OR AFTER INCIDENT, BUT ACFT DID RPT SEEING EACH OTHER. RPTR SAYS SAME THING HAPPENED TO RADIO ABOUT 10 DAYS LATER, COULD BE A JACK PROB.

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.