Improper spacing between 3 aircraft at FL280 results in a loss of separation.

Attributes
ACN	608896
Time
Date	200402
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : pxv.vortac
State Reference	IN
Altitude	msl single value : 28000
Environment
Flight Conditions	VMC
Weather Elements	Turbulence
Light	Night
Aircraft 1
Controlling Facilities	artcc : zid.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
Route In Use	arrival : on vectors arrival star : mosey
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zid.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
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 6.5
ASRS Report	608896
Person 2
Affiliation	government : faa
Function	controller : handoff position controller : radar
Qualification	controller : radar
Experience	controller radar : 6
ASRS Report	608895
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment : conflict alert other controllera other controllerb other flight crewa other flight crewb other other : 5
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Consequence	faa : investigated
Miss Distance	horizontal : 24000 vertical : 0
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft X had to be descended to FL280 for multiple nebound traffic at FL290. I could not descend aircraft X because of additional nebound traffic at FL270. Aircraft X was cleared to abb to accomplish cvg spacing. This would allow aircraft X to be sequenced to cvg but still allow aircraft X to stay south of aircraft Y. Aircraft Y was put on present heading because I could not turn him north because of aircraft Z also at FL280. I then turned aircraft X to a 180 degree heading to maintain separation. Supplemental information from acn 608895: the problem arose because one of the inbound aircraft (aircraft X) was cut short on the mosey arrival for sequencing. Many contributing factors led up to this event. Chop in the higher station pushed same aircraft lower. The fairly complex spacing problem was just winding down. Part of this complexity was the knee jerk request by cvg approach to descend a luk inbound below 9000 ft. Usually these aircraft are left higher and worked in the cvg inbound stream. The controller's skill level also played a role.

Original NASA ASRS Text

Title: IMPROPER SPACING BTWN 3 ACFT AT FL280 RESULTS IN A LOSS OF SEPARATION.

Narrative: ACFT X HAD TO BE DSNDED TO FL280 FOR MULTIPLE NEBOUND TFC AT FL290. I COULD NOT DSND ACFT X BECAUSE OF ADDITIONAL NEBOUND TFC AT FL270. ACFT X WAS CLRED TO ABB TO ACCOMPLISH CVG SPACING. THIS WOULD ALLOW ACFT X TO BE SEQUENCED TO CVG BUT STILL ALLOW ACFT X TO STAY S OF ACFT Y. ACFT Y WAS PUT ON PRESENT HDG BECAUSE I COULD NOT TURN HIM N BECAUSE OF ACFT Z ALSO AT FL280. I THEN TURNED ACFT X TO A 180 DEG HDG TO MAINTAIN SEPARATION. SUPPLEMENTAL INFO FROM ACN 608895: THE PROB AROSE BECAUSE ONE OF THE INBOUND ACFT (ACFT X) WAS CUT SHORT ON THE MOSEY ARR FOR SEQUENCING. MANY CONTRIBUTING FACTORS LED UP TO THIS EVENT. CHOP IN THE HIGHER STATION PUSHED SAME ACFT LOWER. THE FAIRLY COMPLEX SPACING PROB WAS JUST WINDING DOWN. PART OF THIS COMPLEXITY WAS THE KNEE JERK REQUEST BY CVG APCH TO DSND A LUK INBOUND BELOW 9000 FT. USUALLY THESE ACFT ARE LEFT HIGHER AND WORKED IN THE CVG INBOUND STREAM. THE CTLR'S SKILL LEVEL ALSO PLAYED A ROLE.

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.