ALT EXCURSION DURING MAINT TEST OF AUTOPLT.

Narrative

THE PURPOSE OF THE FLT WAS A MAINT 'TEST HOP' TO VERIFY SOME SQUAWKS AND EVALUATE SOME CORRECTIVE ACTIONS. 2 OF THE SYS BEING EVALUATED WERE THE AUTOPLT AND PRESSURIZATION. 1 MECH WAS IN THE R FRONT SEAT WORKING SYS; ANOTHER WAS IN THE BACK TAKING NOTES. THE PRESSURIZATION TEST REQUIRED A CLB TO FL200. I RECEIVED A 'POP-UP' IFR CLRNC FROM CNO GND CTL. I DEPARTED CNO AND TURNED TOWARD PDZ VOR. THE CLRNC INCLUDED A TURN TO JOIN V16 EBOUND TOWARD TRM VOR. SOCAL TRACON ISSUED SEVERAL INTERMEDIATE LEVELOFFS; INCLUDING ONE TO MAINTAIN 9000 FT MSL FOR OPPOSING TFC ON V16 (THE CITATION). I HAD BEEN USING THE AUTOPLT FOR MOST OF THE FLT -- TESTING THE VARIOUS MODES. I ENGAGED 'ALT HOLD' AT 9000 FT AND DIVERTED MY ATTN TO HELPING THE MECH WITH ANOTHER SYS. THE ALT ALERTER CHIME BROUGHT MY ATTN BACK TO THE ALTIMETER. THE AUTOPLT HAD TRIMMED THE AIRPLANE FULL NOSE UP; AND WE WERE AT 9500 FT MSL AND CLBING RAPIDLY. I INITIATED AN IMMEDIATE DSNDING R TURN JUST AS THE CTLR GAVE EVASIVE INSTRUCTIONS TO BOTH ME AND THE CITATION. CTLR ADVISED LOSS OF IFR SEPARATION DOWN TO 200 FT AND 1/2 MI. FUTURE MAINT FLTS OF THIS TYPE SHOULD BE LIMITED TO VFR ONLY; OR A SECOND PLT TO ASSIST THE MECHS SHOULD BE ABOARD.