Narrative:

Contacted oak center on frequency 134.37 climbing out of approximately FL190. Controller issued climb clearance to FL290. Asked if FL290 was smooth and if so, would request FL290 as a final crs altitude. Oak center said, 'maintain FL290.' I read back on 4 separate occasions, 'maintain FL290.' climbing out of FL255 oak center asked us to check our altitude. I replied, '(our identify) climbing out of FL255 for FL290.' oak center said, 'negative, you were not clrd to FL290, but FL250. Maintain FL260, traffic 1 O'clock, 5 mi FL260.' traffic was in sight at all times. No evasive action required. I do believe that oak center originally clrd us to FL290, not FL250. If not, there was a serious communication error in light of the fact that I read back 'clrd to FL290' 4 times. Filed crs altitude was FL330. Note: a subsequent telephone conversation with supervisor at oak center who reviewed the ATC tapes revealed that the controller did say FL250 and that I read back FL290--neither controller or myself caught the error. More precise pronunciation of the numbers would have helped prevent this incident. Supplemental information from acn 80703: we confirmed FL290 on every radio transmission and the oak center controller had always said FL250. I asked was 'niner' used to further clarify 'nine' and he stated we had said clearly 'niner zero.'

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Original NASA ASRS Text

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

Narrative: CONTACTED OAK CENTER ON FREQ 134.37 CLBING OUT OF APPROX FL190. CTLR ISSUED CLB CLRNC TO FL290. ASKED IF FL290 WAS SMOOTH AND IF SO, WOULD REQUEST FL290 AS A FINAL CRS ALT. OAK CENTER SAID, 'MAINTAIN FL290.' I READ BACK ON 4 SEPARATE OCCASIONS, 'MAINTAIN FL290.' CLBING OUT OF FL255 OAK CENTER ASKED US TO CHK OUR ALT. I REPLIED, '(OUR IDENT) CLBING OUT OF FL255 FOR FL290.' OAK CENTER SAID, 'NEGATIVE, YOU WERE NOT CLRD TO FL290, BUT FL250. MAINTAIN FL260, TFC 1 O'CLOCK, 5 MI FL260.' TFC WAS IN SIGHT AT ALL TIMES. NO EVASIVE ACTION REQUIRED. I DO BELIEVE THAT OAK CENTER ORIGINALLY CLRD US TO FL290, NOT FL250. IF NOT, THERE WAS A SERIOUS COM ERROR IN LIGHT OF THE FACT THAT I READ BACK 'CLRD TO FL290' 4 TIMES. FILED CRS ALT WAS FL330. NOTE: A SUBSEQUENT TELEPHONE CONVERSATION WITH SUPVR AT OAK CENTER WHO REVIEWED THE ATC TAPES REVEALED THAT THE CTLR DID SAY FL250 AND THAT I READ BACK FL290--NEITHER CTLR OR MYSELF CAUGHT THE ERROR. MORE PRECISE PRONUNCIATION OF THE NUMBERS WOULD HAVE HELPED PREVENT THIS INCIDENT. SUPPLEMENTAL INFORMATION FROM ACN 80703: WE CONFIRMED FL290 ON EVERY RADIO XMISSION AND THE OAK CENTER CTLR HAD ALWAYS SAID FL250. I ASKED WAS 'NINER' USED TO FURTHER CLARIFY 'NINE' AND HE STATED WE HAD SAID CLRLY 'NINER ZERO.'

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.