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

Attributes
ACN	189432
Time
Date	199109
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sux
State Reference	IA
Altitude	msl bound lower : 35000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 24
ASRS Report	189432
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 230 flight time total : 20000 flight time type : 5000
ASRS Report	189738
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 18000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Basically the problem was because the descending air carrier X was being turned, slowed, and descended to accomplish intrail spacing 350 mi from ord. The other factor was overlapping data blocks the altitude of the conflicting air carrier Y was overlapped by another data block. It was discovered by conflict alert and immediate turns were issued of 40 degrees. The aircraft saw each other and had to take no further action. Supplemental information from acn 189738: air carrier X was at cruise maintaining FL370, 70 mi west of mcw VOR assigned to a heading of 040 degree by minneapolis center for other traffic. Center requested a descent to FL330, speed 265 KTS. Descending through FL355 center requested immediate right turn to 080 degree. Turn was made and traffic came into sight and this turn put us clear of air carrier Y by about 3 1/2 mi. It appeared other aircraft was climbing through our altitude and converging. Other aircraft was also given an immediate 40 degree right turn.

Original NASA ASRS Text

Title: ACR X HAD LTSS FROM ACR Y. SYS ERROR.

Narrative: BASICALLY THE PROBLEM WAS BECAUSE THE DSNDING ACR X WAS BEING TURNED, SLOWED, AND DSNDED TO ACCOMPLISH INTRAIL SPACING 350 MI FROM ORD. THE OTHER FACTOR WAS OVERLAPPING DATA BLOCKS THE ALT OF THE CONFLICTING ACR Y WAS OVERLAPPED BY ANOTHER DATA BLOCK. IT WAS DISCOVERED BY CONFLICT ALERT AND IMMEDIATE TURNS WERE ISSUED OF 40 DEGS. THE ACFT SAW EACH OTHER AND HAD TO TAKE NO FURTHER ACTION. SUPPLEMENTAL INFO FROM ACN 189738: ACR X WAS AT CRUISE MAINTAINING FL370, 70 MI W OF MCW VOR ASSIGNED TO A HDG OF 040 DEG BY MINNEAPOLIS CENTER FOR OTHER TFC. CENTER REQUESTED A DSCNT TO FL330, SPD 265 KTS. DSNDING THROUGH FL355 CENTER REQUESTED IMMEDIATE R TURN TO 080 DEG. TURN WAS MADE AND TFC CAME INTO SIGHT AND THIS TURN PUT US CLR OF ACR Y BY ABOUT 3 1/2 MI. IT APPEARED OTHER ACFT WAS CLBING THROUGH OUR ALT AND CONVERGING. OTHER ACFT WAS ALSO GIVEN AN IMMEDIATE 40 DEG R TURN.

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.