Narrative:

Flight plan filed from pbi-msp. We were climbing to (what we thought was) FL220. Center had cleared us to FL200. We were looking for traffic that center advised was in our 8 O'clock position at FL210. We even commented that this was strange since we would be climbing through that altitude. Center advised that he showed FL206 on altitude readout and instructed us to return to FL200. Shortly after returning to FL200, we were cleared to a higher altitude. Center advised that they would be checking the tapes. We contacted center by phone the following day. We were only cleared to FL200, and we had rogered FL200. The copilot had set FL220 in the altitude alerter, but read back FL200 to center. Obviously, both of us made a mistake. I should have been more aware of the altitude calls, and what was being set in the altitude alerter. Again, we may be relying on the altitude alerter too much and not paying enough attention to basic instrument readout in addition to the obvious. Listen to the radio calls! The ATC tape showed our highest altitude to be 20700', with a vertical sep of 300' and latitude sep of 3.7 mi. This sep was from an large transport at FL210.

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Original NASA ASRS Text

Title: THOUGHT CLEARED TO FL220. CLRNC AS ISSUED AND ACKNOWLEDGED FL200. LESS THAN STANDARD SEPARATION.

Narrative: FLT PLAN FILED FROM PBI-MSP. WE WERE CLBING TO (WHAT WE THOUGHT WAS) FL220. CENTER HAD CLRED US TO FL200. WE WERE LOOKING FOR TFC THAT CENTER ADVISED WAS IN OUR 8 O'CLOCK POS AT FL210. WE EVEN COMMENTED THAT THIS WAS STRANGE SINCE WE WOULD BE CLBING THROUGH THAT ALT. CENTER ADVISED THAT HE SHOWED FL206 ON ALT READOUT AND INSTRUCTED US TO RETURN TO FL200. SHORTLY AFTER RETURNING TO FL200, WE WERE CLRED TO A HIGHER ALT. CENTER ADVISED THAT THEY WOULD BE CHKING THE TAPES. WE CONTACTED CENTER BY PHONE THE FOLLOWING DAY. WE WERE ONLY CLRED TO FL200, AND WE HAD ROGERED FL200. THE COPLT HAD SET FL220 IN THE ALT ALERTER, BUT READ BACK FL200 TO CENTER. OBVIOUSLY, BOTH OF US MADE A MISTAKE. I SHOULD HAVE BEEN MORE AWARE OF THE ALT CALLS, AND WHAT WAS BEING SET IN THE ALT ALERTER. AGAIN, WE MAY BE RELYING ON THE ALT ALERTER TOO MUCH AND NOT PAYING ENOUGH ATTN TO BASIC INSTRUMENT READOUT IN ADDITION TO THE OBVIOUS. LISTEN TO THE RADIO CALLS! THE ATC TAPE SHOWED OUR HIGHEST ALT TO BE 20700', WITH A VERT SEP OF 300' AND LAT SEP OF 3.7 MI. THIS SEP WAS FROM AN LGT AT FL210.

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.