Narrative:

Air carrier Y swbnd 10W/iad at FL200. Climbed air carrier X dca westbound to FL270. Thought I had issued FL190. As aircraft approached each other I noticed air carrier X at FL192 and questioned his clearance. He advised he was climbing to FL270 (tapes confirm this clearance). Turned air carrier X and issued traffic. I issued traffic to air carrier Y. Aircraft passed with less than minimum separation. No C/a activated. Supplemental information from acn 149655: while departing dca air carrier X was in a climb toward the west when incident occurred. We had been level at 17000' and under control of dulles departure. Upon handoff to ZDC the controller cleared us to climb to FL270, which I acknowledged. While passing FL198, however the controller asked if we were level at FL190. (He claims he only cleared us to that altitude.) when we told him that we were climbing to FL270, he told us to make an immediate right turn to 360 degrees (from our present heading of 260 degrees) and advised that we had eastbound air carrier Y at 12 O'clock and 5 mi, FL200. We did as he requested. To our knowledge there was not any danger of colliding with any traffic. Although he claims that he only cleared us to FL190, he later stated that, 'if I gave you 270, then I made an error.' both the captain and I are sure he cleared us to FL270. We were not anticipating that altitude and when it was given we both confirmed it aurally and I read back FL270, to which the controller responded 'affirmative.'

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Original NASA ASRS Text

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

Narrative: ACR Y SWBND 10W/IAD AT FL200. CLBED ACR X DCA WBND TO FL270. THOUGHT I HAD ISSUED FL190. AS ACFT APCHED EACH OTHER I NOTICED ACR X AT FL192 AND QUESTIONED HIS CLRNC. HE ADVISED HE WAS CLBING TO FL270 (TAPES CONFIRM THIS CLRNC). TURNED ACR X AND ISSUED TFC. I ISSUED TFC TO ACR Y. ACFT PASSED WITH LESS THAN MINIMUM SEPARATION. NO C/A ACTIVATED. SUPPLEMENTAL INFO FROM ACN 149655: WHILE DEPARTING DCA ACR X WAS IN A CLB TOWARD THE W WHEN INCIDENT OCCURRED. WE HAD BEEN LEVEL AT 17000' AND UNDER CTL OF DULLES DEP. UPON HDOF TO ZDC THE CTLR CLRED US TO CLB TO FL270, WHICH I ACKNOWLEDGED. WHILE PASSING FL198, HOWEVER THE CTLR ASKED IF WE WERE LEVEL AT FL190. (HE CLAIMS HE ONLY CLRED US TO THAT ALT.) WHEN WE TOLD HIM THAT WE WERE CLBING TO FL270, HE TOLD US TO MAKE AN IMMEDIATE RIGHT TURN TO 360 DEGS (FROM OUR PRESENT HDG OF 260 DEGS) AND ADVISED THAT WE HAD EBND ACR Y AT 12 O'CLOCK AND 5 MI, FL200. WE DID AS HE REQUESTED. TO OUR KNOWLEDGE THERE WAS NOT ANY DANGER OF COLLIDING WITH ANY TFC. ALTHOUGH HE CLAIMS THAT HE ONLY CLRED US TO FL190, HE LATER STATED THAT, 'IF I GAVE YOU 270, THEN I MADE AN ERROR.' BOTH THE CAPT AND I ARE SURE HE CLRED US TO FL270. WE WERE NOT ANTICIPATING THAT ALT AND WHEN IT WAS GIVEN WE BOTH CONFIRMED IT AURALLY AND I READ BACK FL270, TO WHICH THE CTLR RESPONDED 'AFFIRMATIVE.'

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.