Air carrier Y had less than standard separation from air carrier X. System error.

Attributes
ACN	130638
Time
Date	198912
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : bgr
State Reference	ME
Altitude	msl bound lower : 31000 msl bound upper : 31000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 4 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : flight data
Qualification	controller : non radar
ASRS Report	130638
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 24000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

The air carrier X aircraft was at FL310 swbnd and the air carrier Y was being vectored behind the air carrier X. The air carrier Y was descending to FL290 from FL350. I was working the radar associated position when the radar controller was vectoring the aircraft in trail. When I first observed the possible conflict the radar controller turned the air carrier Y from a heading of 190 degrees to a heading of 170 degrees. The C/a had gone off at about the same time I observed a possible conflict and the aircraft were about 30 mi apart. At about the time the heading of 170 degrees was issued, the C/a terminated and it appeared sufficient action had been taken to avoid a conflict. When the aircraft were about 7-10 mi apart they still appeared to be in conflict and the radar controller took additional action by expediting the descent to FL290 for the air carrier Y. However, sep was lost between the 2 aircraft.

Original NASA ASRS Text

Title: ACR Y HAD LESS THAN STANDARD SEPARATION FROM ACR X. SYSTEM ERROR.

Narrative: THE ACR X ACFT WAS AT FL310 SWBND AND THE ACR Y WAS BEING VECTORED BEHIND THE ACR X. THE ACR Y WAS DSNDING TO FL290 FROM FL350. I WAS WORKING THE RADAR ASSOCIATED POS WHEN THE RADAR CTLR WAS VECTORING THE ACFT IN TRAIL. WHEN I FIRST OBSERVED THE POSSIBLE CONFLICT THE RADAR CTLR TURNED THE ACR Y FROM A HDG OF 190 DEGS TO A HDG OF 170 DEGS. THE C/A HAD GONE OFF AT ABOUT THE SAME TIME I OBSERVED A POSSIBLE CONFLICT AND THE ACFT WERE ABOUT 30 MI APART. AT ABOUT THE TIME THE HDG OF 170 DEGS WAS ISSUED, THE C/A TERMINATED AND IT APPEARED SUFFICIENT ACTION HAD BEEN TAKEN TO AVOID A CONFLICT. WHEN THE ACFT WERE ABOUT 7-10 MI APART THEY STILL APPEARED TO BE IN CONFLICT AND THE RADAR CTLR TOOK ADDITIONAL ACTION BY EXPEDITING THE DSCNT TO FL290 FOR THE ACR Y. HOWEVER, SEP WAS LOST BTWN THE 2 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.