ZAU lost separation on crossover descent incident.

Attributes
ACN	575693
Time
Date	200303
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	intersection : story
State Reference	IL
Altitude	msl single value : 9000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc tower : vgt.tower
Operator	general aviation : corporate
Make Model Name	Jetstar 1329 (C140)
Operating Under FAR Part	Part 91
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 13.5
ASRS Report	575693
Person 2
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne critical non adherence : required legal separation
Independent Detector	atc equipment : conflict alert other controllera
Resolutory Action	none taken : detected after the fact other
Consequence	faa : investigated
Miss Distance	horizontal : 16200 vertical : 900
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was trying to get aircraft X under crossing traffic and turn to ugn so I could descend an old lander from the north. I felt that I was clear of the pmy arrival, and I was concerned about getting under the 11000 ft sebound through sector (which is not normal). I asked aircraft X to expedite through 10000 ft within 2 1/2 mins and then direct ugn leaving 10000 ft. I didn't expect the rate of descent to be so drastic. The 2 1/2 mins was well clear of V84 when I noticed the conflict. I stopped aircraft X at 9000 ft and tried to ask aircraft Y his altitude. I was distraction by the ord sequencing problem in the eastern portion of the sector.

Original NASA ASRS Text

Title: ZAU LOST SEPARATION ON CROSSOVER DSCNT INCIDENT.

Narrative: I WAS TRYING TO GET ACFT X UNDER XING TFC AND TURN TO UGN SO I COULD DSND AN OLD LANDER FROM THE N. I FELT THAT I WAS CLR OF THE PMY ARR, AND I WAS CONCERNED ABOUT GETTING UNDER THE 11000 FT SEBOUND THROUGH SECTOR (WHICH IS NOT NORMAL). I ASKED ACFT X TO EXPEDITE THROUGH 10000 FT WITHIN 2 1/2 MINS AND THEN DIRECT UGN LEAVING 10000 FT. I DIDN'T EXPECT THE RATE OF DSCNT TO BE SO DRASTIC. THE 2 1/2 MINS WAS WELL CLR OF V84 WHEN I NOTICED THE CONFLICT. I STOPPED ACFT X AT 9000 FT AND TRIED TO ASK ACFT Y HIS ALT. I WAS DISTR BY THE ORD SEQUENCING PROB IN THE EASTERN PORTION OF THE SECTOR.

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.