Narrative:

During climb out from gso, numerous incremental climb clrncs were received. One such clearance was understood by both myself (the PNF) and the PF to be 'climb and maintain FL290.' the readback was 'roger, FL290, (call sign).' FL290 was set in the altitude alerting device, and climb was initiated. During this period, a handoff was accomplished to another ARTCC sector. Approaching leveloff at FL290, a TA was received and a target was observed at 10 O'clock position, slightly higher, opposite direction, with a lateral separation of 4.5 mi. Shortly thereafter, the controller queried us as to our altitude. Upon our reply, he stated he believed the prior controller 'wanted us at FL280.' we confirmed within the cockpit that we had heard and read back FL290, then relayed this information to the controller. He seemed unconcerned, and simply assigned us a higher altitude to continue our climb. Based upon the traffic conflict, it seems likely the prior controller wanted us at FL280. If so, either he verbally assigned FL290 in error or we heard, and read back, FL290 in error. In either case, the controller failed to catch, and correct, the error upon readback.

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Original NASA ASRS Text

Title: AN APPARENT READBACK AND OR HEARBACK ERROR RESULTED IN A C750 FLT CREW TO CLB TO A WRONG ALT.

Narrative: DURING CLBOUT FROM GSO, NUMEROUS INCREMENTAL CLB CLRNCS WERE RECEIVED. ONE SUCH CLRNC WAS UNDERSTOOD BY BOTH MYSELF (THE PNF) AND THE PF TO BE 'CLB AND MAINTAIN FL290.' THE READBACK WAS 'ROGER, FL290, (CALL SIGN).' FL290 WAS SET IN THE ALT ALERTING DEVICE, AND CLB WAS INITIATED. DURING THIS PERIOD, A HDOF WAS ACCOMPLISHED TO ANOTHER ARTCC SECTOR. APCHING LEVELOFF AT FL290, A TA WAS RECEIVED AND A TARGET WAS OBSERVED AT 10 O'CLOCK POS, SLIGHTLY HIGHER, OPPOSITE DIRECTION, WITH A LATERAL SEPARATION OF 4.5 MI. SHORTLY THEREAFTER, THE CTLR QUERIED US AS TO OUR ALT. UPON OUR REPLY, HE STATED HE BELIEVED THE PRIOR CTLR 'WANTED US AT FL280.' WE CONFIRMED WITHIN THE COCKPIT THAT WE HAD HEARD AND READ BACK FL290, THEN RELAYED THIS INFO TO THE CTLR. HE SEEMED UNCONCERNED, AND SIMPLY ASSIGNED US A HIGHER ALT TO CONTINUE OUR CLB. BASED UPON THE TFC CONFLICT, IT SEEMS LIKELY THE PRIOR CTLR WANTED US AT FL280. IF SO, EITHER HE VERBALLY ASSIGNED FL290 IN ERROR OR WE HEARD, AND READ BACK, FL290 IN ERROR. IN EITHER CASE, THE CTLR FAILED TO CATCH, AND CORRECT, THE ERROR UPON READBACK.

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.