Less than standard separation incident when large transport descended through altitude of small tran...

Attributes
ACN	98303
Time
Date	198811
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : alb
State Reference	NY
Altitude	msl bound lower : 22800 msl bound upper : 23000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute airway : zbw
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 7
ASRS Report	98303
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation other anomaly other
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	none taken : anomaly accepted none taken : unable
Consequence	faa : investigated
Miss Distance	horizontal : 18000 vertical : 200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error Intra Facility Coordination Failure

Narrative:

Large transport X was given clearance that put him in confliction with small transport Y the receiving controller recognized this and told me to stop large transport X 1000' above small transport Y. I agreed that large transport X was in confliction with small transport Y and should be stopped 1000' above, however I had already transferred large transport X to the receiving controller. As it turns out, large transport X never acknowledged the frequency change and descended through small transport Y the sector was busy most of the day and it was at shift change when the error occurred. I believe it was a classic case of letting one's guard down a moment too soon. I had to be paged back to the sector as I was walking out of the bldg. Clearer communications between sectors could have prevented the error. Ensuring pilot acknowledgement. Callback conversation with reporter revealed the following: callback to determine location of the incident and the type of aircraft involved. Sep was 3 NM and 200'. Reporter was working a combined position operation. Experience level was 7 yrs and traffic vol was light. Incident happened in the athens sector airspace. Reporter had been relieved and gave his relief a briefing, but also had told him that the large transport had made a frequency change. Reporter was on his way out of the bldg and was paged back to the control room as the incident was charged to him.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION INCIDENT WHEN LGT DESCENDED THROUGH ALT OF SMT, FREQ CHANGE MISSED BY LGT. INCORRECT POSITION RELIEF BRIEFING.

Narrative: LGT X WAS GIVEN CLRNC THAT PUT HIM IN CONFLICTION WITH SMT Y THE RECEIVING CTLR RECOGNIZED THIS AND TOLD ME TO STOP LGT X 1000' ABOVE SMT Y. I AGREED THAT LGT X WAS IN CONFLICTION WITH SMT Y AND SHOULD BE STOPPED 1000' ABOVE, HOWEVER I HAD ALREADY TRANSFERRED LGT X TO THE RECEIVING CTLR. AS IT TURNS OUT, LGT X NEVER ACKNOWLEDGED THE FREQ CHANGE AND DSNDED THROUGH SMT Y THE SECTOR WAS BUSY MOST OF THE DAY AND IT WAS AT SHIFT CHANGE WHEN THE ERROR OCCURRED. I BELIEVE IT WAS A CLASSIC CASE OF LETTING ONE'S GUARD DOWN A MOMENT TOO SOON. I HAD TO BE PAGED BACK TO THE SECTOR AS I WAS WALKING OUT OF THE BLDG. CLEARER COMS BTWN SECTORS COULD HAVE PREVENTED THE ERROR. ENSURING PLT ACKNOWLEDGEMENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: CALLBACK TO DETERMINE LOCATION OF THE INCIDENT AND THE TYPE OF ACFT INVOLVED. SEP WAS 3 NM AND 200'. RPTR WAS WORKING A COMBINED POS OPERATION. EXPERIENCE LEVEL WAS 7 YRS AND TFC VOL WAS LIGHT. INCIDENT HAPPENED IN THE ATHENS SECTOR AIRSPACE. RPTR HAD BEEN RELIEVED AND GAVE HIS RELIEF A BRIEFING, BUT ALSO HAD TOLD HIM THAT THE LGT HAD MADE A FREQ CHANGE. RPTR WAS ON HIS WAY OUT OF THE BLDG AND WAS PAGED BACK TO THE CTL ROOM AS THE INCIDENT WAS CHARGED TO HIM.

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.

Less than standard separation incident when large transport descended through altitude of small transport, frequency change missed by large transport. Incorrect position relief briefing.