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

Attributes
ACN	141194
Time
Date	199003
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : eon
State Reference	IL
Altitude	msl bound lower : 24000 msl bound upper : 24500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
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	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 2 controller radar : 2
ASRS Report	141194
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 24600 vertical : 400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Traffic in the sector was 1) slow swbnd overflt at FL240. 2) slow eastbound overflt at FL250. 3) southbound overflt traffic on J73, numerous J73 departures off ord and mdw. Air carrier X called on frequency and was cleared to FL240, assigned a 220 heading, 250 KTS to get in trail with a J73 overflt. Air carrier Y called on frequency (7 mi in trail of air carrier X and about 1 mi west) on a 160 heading, 280 KTS. Air carrier Y was turned to a 180 heading (traffic climbing over rbs prevented further turns west) and climbed to FL270. When air carrier Y showed FL238 in the data block, I noticed the conflict and turned air carrier Y to a 240 heading and stopped him at FL240. I turned air carrier X to a 180 heading and expedited to FL250. Contributing factors: 1) wind at FL240 - 240/140 KTS. 2) mode C lag (when air carrier Y showed FL238 he was actually at around FL243-FL245). 3) controller awareness - I never should have climbed air carrier X or expedited him through FL250.

Original NASA ASRS Text

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

Narrative: TFC IN THE SECTOR WAS 1) SLOW SWBND OVERFLT AT FL240. 2) SLOW EBND OVERFLT AT FL250. 3) SBND OVERFLT TFC ON J73, NUMEROUS J73 DEPS OFF ORD AND MDW. ACR X CALLED ON FREQ AND WAS CLRED TO FL240, ASSIGNED A 220 HDG, 250 KTS TO GET IN TRAIL WITH A J73 OVERFLT. ACR Y CALLED ON FREQ (7 MI IN TRAIL OF ACR X AND ABOUT 1 MI W) ON A 160 HDG, 280 KTS. ACR Y WAS TURNED TO A 180 HDG (TFC CLIMBING OVER RBS PREVENTED FURTHER TURNS WEST) AND CLIMBED TO FL270. WHEN ACR Y SHOWED FL238 IN THE DATA BLOCK, I NOTICED THE CONFLICT AND TURNED ACR Y TO A 240 HDG AND STOPPED HIM AT FL240. I TURNED ACR X TO A 180 HDG AND EXPEDITED TO FL250. CONTRIBUTING FACTORS: 1) WIND AT FL240 - 240/140 KTS. 2) MODE C LAG (WHEN ACR Y SHOWED FL238 HE WAS ACTUALLY AT AROUND FL243-FL245). 3) CTLR AWARENESS - I NEVER SHOULD HAVE CLIMBED ACR X OR EXPEDITED HIM THROUGH FL250.

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.