ARTCC radar controller split up a combined sector operation and thought he had all the aircraft on the split sector's frequency. Later the other sector controller observed a potential conflict and had the reporter check for an air carrier aircraft he couldn't talk with. The air carrier had missed the frequency change and the reporter was able to descend the aircraft to prevent a loss of separation.

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Attributes
ACN	389147
Time
Date	199712
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : psk
State Reference	VA
Altitude	msl bound lower : 31000 msl bound upper : 31000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl tower : sav
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar pilot : student
Experience	controller radar : 16 flight time total : 10
ASRS Report	389147
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Miss Distance	vertical : 2000
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	other
Situations
ATC Facility	procedure or policy : unspecified

Narrative:

Psk (ZTL 43) and salem (ZTL 42) were combined on 43. The sectors are identical geographically. Psk owns FL240- FL290, salem owns FL310-FL330. The supervisor was late in splitting the sector. The controller I relieved had been using both frequencys in running the sector. As salem was taken off, I turned off 120.72 (frequency for salem). Before dropping the data blocks on aircraft now in salem, I switch the aircraft to 120.72. If there is no response, I assume the aircraft is already on 120.72. An air carrier B727 missed the frequency change. Several mins later he was in conflict with another aircraft. The salem controller called and asked me to try the air carrier. The air carrier answered and I descended the aircraft. When possible, no more than 1 frequency should be used to operate a sector. Despite numerous requests, the FAA hasn't set this as an SOP and many controllers still use both frequencys.

Original NASA ASRS Text

Title: ARTCC RADAR CTLR SPLIT UP A COMBINED SECTOR OP AND THOUGHT HE HAD ALL THE ACFT ON THE SPLIT SECTOR'S FREQ. LATER THE OTHER SECTOR CTLR OBSERVED A POTENTIAL CONFLICT AND HAD THE RPTR CHK FOR AN ACR ACFT HE COULDN'T TALK WITH. THE ACR HAD MISSED THE FREQ CHANGE AND THE RPTR WAS ABLE TO DSND THE ACFT TO PREVENT A LOSS OF SEPARATION.

Narrative: PSK (ZTL 43) AND SALEM (ZTL 42) WERE COMBINED ON 43. THE SECTORS ARE IDENTICAL GEOGRAPHICALLY. PSK OWNS FL240- FL290, SALEM OWNS FL310-FL330. THE SUPVR WAS LATE IN SPLITTING THE SECTOR. THE CTLR I RELIEVED HAD BEEN USING BOTH FREQS IN RUNNING THE SECTOR. AS SALEM WAS TAKEN OFF, I TURNED OFF 120.72 (FREQ FOR SALEM). BEFORE DROPPING THE DATA BLOCKS ON ACFT NOW IN SALEM, I SWITCH THE ACFT TO 120.72. IF THERE IS NO RESPONSE, I ASSUME THE ACFT IS ALREADY ON 120.72. AN ACR B727 MISSED THE FREQ CHANGE. SEVERAL MINS LATER HE WAS IN CONFLICT WITH ANOTHER ACFT. THE SALEM CTLR CALLED AND ASKED ME TO TRY THE ACR. THE ACR ANSWERED AND I DSNDED THE ACFT. WHEN POSSIBLE, NO MORE THAN 1 FREQ SHOULD BE USED TO OPERATE A SECTOR. DESPITE NUMEROUS REQUESTS, THE FAA HASN'T SET THIS AS AN SOP AND MANY CTLRS STILL USE BOTH FREQS.

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.