Close proximity air carrier large transport unknown aircraft while on descent to ord.

Attributes
ACN	146537
Time
Date	199005
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : obk
State Reference	IL
Altitude	msl bound lower : 8500 msl bound upper : 10000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute airway : zau
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 55 flight time total : 5778
ASRS Report	146537
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot conflict : nmac
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	unspecified : 500
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	Pilot Deviation Operational Error other

Narrative:

During descent we were cleared to cross 35 east of northbrook VOR at 10000'. Prior to reaching 10000' we were subsequently cleared to descend to 8000'. At about 8500' center said 'level at 8500''. We then saw traffic off the left and passed by about 500' clear of this traffic. Thereafter we descended to 8000' and continued to destination west/O further incident. Center said he thought he had told us to stay at 10000' but I don't think that he ever cancelled the 8000' clearance. 'See and be seen.'

Original NASA ASRS Text

Title: CLOSE PROX ACR LGT UNKNOWN ACFT WHILE ON DESCENT TO ORD.

Narrative: DURING DSNT WE WERE CLRED TO CROSS 35 E OF NORTHBROOK VOR AT 10000'. PRIOR TO REACHING 10000' WE WERE SUBSEQUENTLY CLRED TO DSND TO 8000'. AT ABOUT 8500' CTR SAID 'LEVEL AT 8500''. WE THEN SAW TFC OFF THE L AND PASSED BY ABOUT 500' CLR OF THIS TFC. THEREAFTER WE DSNDED TO 8000' AND CONTINUED TO DEST W/O FURTHER INCIDENT. CTR SAID HE THOUGHT HE HAD TOLD US TO STAY AT 10000' BUT I DON'T THINK THAT HE EVER CANCELLED THE 8000' CLRNC. 'SEE AND BE SEEN.'

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.