Narrative:

I was cleared to climb to FL200. I had the autoplt engaged, and as I approached my assigned altitude, the autoplt annunciated altitude capture. I was then distraction by programming a waypoint into the GPS. The other aircraft (a marine aircraft) called ZDC asking about traffic on radar. He said he had an RA and was climbing. Center controller asked me for my altitude. It was indicating between FL206 and FL207. I immediately descended back to altitude of FL200. The autoplt had not actually captured the altitude, but had not annunciated any malfunction. The next controller asked me to call the ZDC supervisor when I landed, which I did. The autoplt had several momentary 'autoplt trim fail' light annunciations later in the flight. These occurrences were reported for maintenance action. My distraction with GPS waypoint entry and reliance on the autoplt automated altitude capture function caused this situation. I was told by the center supervisor that the conflict was captured by their system electronically. The marine aircraft had climbed to FL213, while I was at FL207, a difference of 600 ft. My aircraft is not TCASII equipped. Fortunately, the marine aircraft had TCASII.

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Original NASA ASRS Text

Title: BE20 PLT CLBING TO FL200 BECOMES DISTR, OVERSHOT ASSIGNED ALT, AND CONFLICTS WITH MIL TFC AT FL210.

Narrative: I WAS CLRED TO CLB TO FL200. I HAD THE AUTOPLT ENGAGED, AND AS I APCHED MY ASSIGNED ALT, THE AUTOPLT ANNUNCIATED ALT CAPTURE. I WAS THEN DISTR BY PROGRAMMING A WAYPOINT INTO THE GPS. THE OTHER ACFT (A MARINE ACFT) CALLED ZDC ASKING ABOUT TFC ON RADAR. HE SAID HE HAD AN RA AND WAS CLBING. CTR CTLR ASKED ME FOR MY ALT. IT WAS INDICATING BTWN FL206 AND FL207. I IMMEDIATELY DSNDED BACK TO ALT OF FL200. THE AUTOPLT HAD NOT ACTUALLY CAPTURED THE ALT, BUT HAD NOT ANNUNCIATED ANY MALFUNCTION. THE NEXT CTLR ASKED ME TO CALL THE ZDC SUPVR WHEN I LANDED, WHICH I DID. THE AUTOPLT HAD SEVERAL MOMENTARY 'AUTOPLT TRIM FAIL' LIGHT ANNUNCIATIONS LATER IN THE FLT. THESE OCCURRENCES WERE RPTED FOR MAINT ACTION. MY DISTR WITH GPS WAYPOINT ENTRY AND RELIANCE ON THE AUTOPLT AUTOMATED ALT CAPTURE FUNCTION CAUSED THIS SIT. I WAS TOLD BY THE CTR SUPVR THAT THE CONFLICT WAS CAPTURED BY THEIR SYS ELECTRONICALLY. THE MARINE ACFT HAD CLBED TO FL213, WHILE I WAS AT FL207, A DIFFERENCE OF 600 FT. MY ACFT IS NOT TCASII EQUIPPED. FORTUNATELY, THE MARINE ACFT HAD TCASII.

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.