Controller at ZAU misses a pilot readback resulting in a loss of separation.

Attributes
ACN	439160
Time
Date	199905
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : jot.vortac
State Reference	IL
Altitude	msl single value : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc tracon : c90.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 8 controller radar : 8
ASRS Report	439160
Person 2
Affiliation	government : faa
Function	controller : approach controller : radar
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error
Situations
Airspace Structure	class b : ord.b

Narrative:

A readback was missed, equipment unfamiliarity is a contributing factor, ord approach discovered it and took corrective actions. Callback conversation with reporter revealed the following information: reporter stated he had just relieved the position and was checking the computer readout device about the same time a pilot was reading back his descent clearance. He said his unfamiliarity with the equipment and a nonstandard controller briefing caused him to miss an incorrect readback resulting in a loss of separation.

Original NASA ASRS Text

Title: CTLR AT ZAU MISSES A PLT READBACK RESULTING IN A LOSS OF SEPARATION.

Narrative: A READBACK WAS MISSED, EQUIP UNFAMILIARITY IS A CONTRIBUTING FACTOR, ORD APCH DISCOVERED IT AND TOOK CORRECTIVE ACTIONS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED HE HAD JUST RELIEVED THE POS AND WAS CHKING THE COMPUTER READOUT DEVICE ABOUT THE SAME TIME A PLT WAS READING BACK HIS DSCNT CLRNC. HE SAID HIS UNFAMILIARITY WITH THE EQUIP AND A NONSTANDARD CTLR BRIEFING CAUSED HIM TO MISS AN INCORRECT READBACK RESULTING IN A LOSS OF SEPARATION.

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.