ALTDEV DURING CLBOUT.

Narrative

WE DEPARTED RWY 18L AT CLT; IFR CLRNC TO PHILADELPHIA. PANTHER 2 DEP; MERIL TRANSITION; TO THE RDU 248 DEG RADIAL FLOPS; AS FILED. INITIAL ALT ON SID IS 8000 FT. DEP CTL ISSUED SEVERAL VECTORS TO JOIN THE MERIL TRANSITION. ALSO CLRED US TO EITHER 9000 FT OR 10000 FT. SUBSEQUENTLY CLRED BY DEP TO 15000 FT. BOTH PNF AND MYSELF INDEPENDENTLY HEARD 15000 FT; AND VERIFIED IT WITH EACH OTHER. 15000 FT IS UNUSUAL BECAUSE THE HDOF ALT IS TYPICALLY 12000 FT. PNF WAS GOING TO RECHK BUT WE WERE HANDED OFF TO ZTL AND DECIDED TO RECHK ALT WITH ATLANTA. PNF CHKED IN 'OUT OF 9000 FT CLBING 15000 FT.' CTR RESPONDED 'ROGER.' PASSING 13000 FT; CTR ASKED IF WE WERE LEVEL AT 12000 FT. RESPONDED 'NEGATIVE; CLBING 15000 FT; AS WE RPTED TO YOU.' ATLANTA WANTED TO KNOW WHERE WE GOT THE 15000 FT ALT FROM. WE SAID CLT DEP. HE STATED CLT ASSIGNED 12000 FT. WE WERE INSTRUCTED TO CONTACT THE ZTL CHIEF BY TELEPHONE. ATLANTA HAD US CONTINUE OUR CLB TO 15000 FT. THERE WAS NO APPARENT TFC CONFLICT. IT CONCERNS ME THAT BOTH PLTS UNDERSTOOD 15000 FT; NOT 12000 FT; AND FURTHER THAT; ON OUR CALL-UP TO ZTL; THE ALT WE CALLED (OUT OF 9000 FT CLBING 15000 FT) WAS NOT CORRECTED BY THE CTLR. IT HAS ALWAYS BEEN MY UNDERSTANDING THAT A 'ROGER' REPLY FROM A CTLR INDICATES BOTH UNDERSTANDING AND AGREEMENT.