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

Attributes
ACN	174702
Time
Date	199104
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : gsh
State Reference	IL
Altitude	msl bound lower : 8000 msl bound upper : 9000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau
Operator	common carrier : air carrier
Make Model Name	Medium Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
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 non radar : 1 controller radar : 6
ASRS Report	174702
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
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
Consequence	faa : investigated
Miss Distance	horizontal : 25200 vertical : 400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was vectoring air carrier X and air carrier Y for in-trail spacing to mdw. I apparently transposed their altitudes in my mind and descended air carrier X on top of air carrier Y. They were at 9000 and 8000', respectively. Traffic extremely light. My first error ever. I just went to sleep. I'd had adequate breaks, sleep and on position 25 mins. Callback conversation with reporter revealed the following: reporter stated the incident happened 15 mi west of gsh. Both aircraft were air carrier's. The reporter had been certified on the sector 1 month. The reporter stated he just looked at the wrong data tag and issued descent clearance. C/a activated.

Original NASA ASRS Text

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

Narrative: I WAS VECTORING ACR X AND ACR Y FOR IN-TRAIL SPACING TO MDW. I APPARENTLY TRANSPOSED THEIR ALTS IN MY MIND AND DSNDED ACR X ON TOP OF ACR Y. THEY WERE AT 9000 AND 8000', RESPECTIVELY. TFC EXTREMELY LIGHT. MY FIRST ERROR EVER. I JUST WENT TO SLEEP. I'D HAD ADEQUATE BREAKS, SLEEP AND ON POS 25 MINS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR STATED THE INCIDENT HAPPENED 15 MI W OF GSH. BOTH ACFT WERE ACR'S. THE RPTR HAD BEEN CERTIFIED ON THE SECTOR 1 MONTH. THE RPTR STATED HE JUST LOOKED AT THE WRONG DATA TAG AND ISSUED DSNT CLRNC. C/A ACTIVATED.

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.