Narrative:

We were at 10000' and 210 KTS on an ene-east heading. The controller, who was quite busy at the time, gave us a clearance to descend, to slow and possibly a heading change too. The captain read back cleared to 7000', slow to 170 KTS, etc. The readback was not questioned by the controller. Descending through 7800' to 7500' I saw the lights of an aircraft pass beneath our nose traveling northbound below us and not more than 1 mi ahead. That aircraft apparently was at 7000', although I couldn't tell the vertical distance accurately. The captain started to comment on the aircraft as it emerged from beneath the nose on his side, and as he did, the controller questioned our altitude, in that belief that we should be at 8000'. Chicago controllers work at maximum capacity for much of their shift. They talk too fast trying to do their job, causing the possibility of error. Pilots respond too quickly, increasing the possibility of error, and the controllers don't have time to listen to the readback, further increasing the possibility of error. As a further note, as we were leaving chicago 2 hours later that same evening, we were involved in 2 more communications errors by the controllers. One was on the ground, and the other on departure control. Neither case caused a deviation or problem, but further points out the pressure on the controllers in chicago.

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Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN ACR AND ANOTHER IFR ACFT.

Narrative: WE WERE AT 10000' AND 210 KTS ON AN ENE-E HDG. THE CTLR, WHO WAS QUITE BUSY AT THE TIME, GAVE US A CLRNC TO DSND, TO SLOW AND POSSIBLY A HDG CHANGE TOO. THE CAPT READ BACK CLRED TO 7000', SLOW TO 170 KTS, ETC. THE READBACK WAS NOT QUESTIONED BY THE CTLR. DSNDING THROUGH 7800' TO 7500' I SAW THE LIGHTS OF AN ACFT PASS BENEATH OUR NOSE TRAVELING NBOUND BELOW US AND NOT MORE THAN 1 MI AHEAD. THAT ACFT APPARENTLY WAS AT 7000', ALTHOUGH I COULDN'T TELL THE VERT DISTANCE ACCURATELY. THE CAPT STARTED TO COMMENT ON THE ACFT AS IT EMERGED FROM BENEATH THE NOSE ON HIS SIDE, AND AS HE DID, THE CTLR QUESTIONED OUR ALT, IN THAT BELIEF THAT WE SHOULD BE AT 8000'. CHICAGO CTLRS WORK AT MAX CAPACITY FOR MUCH OF THEIR SHIFT. THEY TALK TOO FAST TRYING TO DO THEIR JOB, CAUSING THE POSSIBILITY OF ERROR. PLTS RESPOND TOO QUICKLY, INCREASING THE POSSIBILITY OF ERROR, AND THE CTLRS DON'T HAVE TIME TO LISTEN TO THE READBACK, FURTHER INCREASING THE POSSIBILITY OF ERROR. AS A FURTHER NOTE, AS WE WERE LEAVING CHICAGO 2 HRS LATER THAT SAME EVENING, WE WERE INVOLVED IN 2 MORE COMS ERRORS BY THE CTLRS. ONE WAS ON THE GND, AND THE OTHER ON DEP CTL. NEITHER CASE CAUSED A DEVIATION OR PROB, BUT FURTHER POINTS OUT THE PRESSURE ON THE CTLRS IN CHICAGO.

Data retrieved from NASA's ASRS site as of August 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.