Narrative:

Dulles departure cleared us to FL200. As we were approaching 17000 ft, departure instructed us to level at 17000 ft. After leveling off at 17000 ft, departure advised of VFR traffic at 11 O'clock, 17500 ft (small transport). We reported traffic in sight. The traffic appeared not to be at 17500 but lower than us and going across the nose of our aircraft. We were then instructed to maintain visual separation. At that instant, the small transport made a climbing turn toward our aircraft, at less than 60 ft of separation. We were on a northwest heading and the small transport was on an ese collision course. The time span between first spotting the small transport and it passing over our left wing was at most 5 to 15 seconds. We were then instructed to contact ZDC. The closure rate was over 600 KTS.

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Original NASA ASRS Text

Title: AN IFR MLG ACR CREW HAD AN NMAC WITH A VFR LTT. ATC STOPPED THE RPTING ACFT'S CLB TO AVOID A COLLISION.

Narrative: DULLES DEP CLRED US TO FL200. AS WE WERE APCHING 17000 FT, DEP INSTRUCTED US TO LEVEL AT 17000 FT. AFTER LEVELING OFF AT 17000 FT, DEP ADVISED OF VFR TFC AT 11 O'CLOCK, 17500 FT (SMT). WE RPTED TFC IN SIGHT. THE TFC APPEARED NOT TO BE AT 17500 BUT LOWER THAN US AND GOING ACROSS THE NOSE OF OUR ACFT. WE WERE THEN INSTRUCTED TO MAINTAIN VISUAL SEPARATION. AT THAT INSTANT, THE SMT MADE A CLBING TURN TOWARD OUR ACFT, AT LESS THAN 60 FT OF SEPARATION. WE WERE ON A NW HDG AND THE SMT WAS ON AN ESE COLLISION COURSE. THE TIME SPAN BTWN FIRST SPOTTING THE SMT AND IT PASSING OVER OUR L WING WAS AT MOST 5 TO 15 SECONDS. WE WERE THEN INSTRUCTED TO CONTACT ZDC. THE CLOSURE RATE WAS OVER 600 KTS.

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.