Narrative:

Air carrier X were being radar vectored for approach to localizer 27R at ord level at 4000' heading 180 degrees 170 KIAS when from our right front, heading eastbound, came air carrier medium large transport Y which descended from above through our assigned altitude as it passed within 1/4-1/3 mi of our nose. When the first officer asked approach, 'what about that air carrier Y that just passed in front of us?', ord approach replied, 'he should have passed behind you.' then he gave us a turn to intercept the localizer 27R and frequency change to a final controller. We were in and out of the clouds at the time and had visibility contact with air carrier Y for only a few seconds.

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Original NASA ASRS Text

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

Narrative: ACR X WERE BEING RADAR VECTORED FOR APCH TO LOC 27R AT ORD LEVEL AT 4000' HDG 180 DEGS 170 KIAS WHEN FROM OUR RIGHT FRONT, HDG EBND, CAME ACR MLG Y WHICH DSNDED FROM ABOVE THROUGH OUR ASSIGNED ALT AS IT PASSED WITHIN 1/4-1/3 MI OF OUR NOSE. WHEN THE F/O ASKED APCH, 'WHAT ABOUT THAT ACR Y THAT JUST PASSED IN FRONT OF US?', ORD APCH REPLIED, 'HE SHOULD HAVE PASSED BEHIND YOU.' THEN HE GAVE US A TURN TO INTERCEPT THE LOC 27R AND FREQ CHANGE TO A FINAL CTLR. WE WERE IN AND OUT OF THE CLOUDS AT THE TIME AND HAD VIS CONTACT WITH ACR Y FOR ONLY A FEW SECS.

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.