Narrative:

Issued a clearance to cross wiske at 10000 ft MSL. Later ATC requested that we 'start down now to 14000 ft.' we interpreted this to mean we were to descend to 14000 ft now and then cross wiske at 10000 ft. A traffic conflict occurred at 13000 ft. TCASII issued a TA correctly since we were passing behind crossing traffic. We saw the traffic just prior to the TCASII TA. The controller called the traffic later. I talked with ZOB by telephone and they were quick to say 'pilot deviation has occurred.' later, after they had listened to the tapes, they said, 'it looks like it was controller error.' supplemental information from acn 339075: descending through 12000 ft, the center said we were supposed to stop at 14000 ft. In the previous center clearance, maintain 14000 ft was never given. There was never any doubt between myself and captain that the 'wiske' at 10000 ft restr was our clearance limit. Supplemental information from acn 339076: I cleared aircraft X to 10000 ft. Shortly afterward, I realized aircraft Y would not be clear of aircraft X route, so I tried to stop aircraft X at 14000 ft. Pilot said ok, but never stopped at 14000 ft and I lost separation with aircraft Y at 13000 ft.

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Original NASA ASRS Text

Title: AN ACR MLG WAS GIVEN AN AMBIGUOUS, IMPROPERLY WORDED DSCNT CLRNC THAT LED TO LTSS.

Narrative: ISSUED A CLRNC TO CROSS WISKE AT 10000 FT MSL. LATER ATC REQUESTED THAT WE 'START DOWN NOW TO 14000 FT.' WE INTERPRETED THIS TO MEAN WE WERE TO DSND TO 14000 FT NOW AND THEN CROSS WISKE AT 10000 FT. A TFC CONFLICT OCCURRED AT 13000 FT. TCASII ISSUED A TA CORRECTLY SINCE WE WERE PASSING BEHIND XING TFC. WE SAW THE TFC JUST PRIOR TO THE TCASII TA. THE CTLR CALLED THE TFC LATER. I TALKED WITH ZOB BY TELEPHONE AND THEY WERE QUICK TO SAY 'PLTDEV HAS OCCURRED.' LATER, AFTER THEY HAD LISTENED TO THE TAPES, THEY SAID, 'IT LOOKS LIKE IT WAS CTLR ERROR.' SUPPLEMENTAL INFO FROM ACN 339075: DSNDING THROUGH 12000 FT, THE CTR SAID WE WERE SUPPOSED TO STOP AT 14000 FT. IN THE PREVIOUS CTR CLRNC, MAINTAIN 14000 FT WAS NEVER GIVEN. THERE WAS NEVER ANY DOUBT BTWN MYSELF AND CAPT THAT THE 'WISKE' AT 10000 FT RESTR WAS OUR CLRNC LIMIT. SUPPLEMENTAL INFO FROM ACN 339076: I CLRED ACFT X TO 10000 FT. SHORTLY AFTERWARD, I REALIZED ACFT Y WOULD NOT BE CLR OF ACFT X RTE, SO I TRIED TO STOP ACFT X AT 14000 FT. PLT SAID OK, BUT NEVER STOPPED AT 14000 FT AND I LOST SEPARATION WITH ACFT Y AT 13000 FT.

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.