ALT BUST AFTER AUTOPLT TRIPS OFF.

Narrative

WHILE IN A RTING CLB FROM FL350 TO FL390 IN A LEAR 36A I ENCOUNTERED MODERATE TO SEVERE CLR AIR TURB. I HAD JUST LEVELED AT FL390 AND HAD ENGAGED THE ALT HOLD OF THE AUTOPLT; THE TURB WAS ENCOUNTERED AT ABOUT THIS TIME. IN THE TURB THE AUTOPLT DISENGAGED AND CONSEQUENTLY WE WERE PLACED IN A NOSE DOWN POS. OUR MACH NUMBER WAS .78 AND WITH THIS PITCH DOWN BEGAN TO INCREASE RAPIDLY. IN AN EFFORT TO DECREASE OUR RATE OF DSCNT I GENTLY APPLIED BACK PRESSURE WHILE DECREASING THE THRUST TO FLT IDLE. AT THIS POINT I IMMEDIATELY ENCOUNTERED AILERON ACTIVITY (BUZZ) AND WAS FORCED TO RELEASE BACK PRESSURE. SLOWLY THE RATE OF DSCNT DECREASED AND I WAS ABLE TO REGAIN CTL. NO DAMAGE WAS DONE TO THE ACFT; ONLY A SHAKEN FLC AND PAX. POSSIBLE WAYS TO PREVENT THIS FROM HAPPENING AGAIN: CRUISE AT LOWER MACH NUMBERS. IN RETROSPECT AN EMER SHOULD HAVE BEEN DECLARED WHEN I REALIZED THAT THE RATE OF DSCNT COULD NOT BE STOPPED. TOTAL ALT LOSS WAS ABOUT 1000 FT AND RECOVERY TO FL390 WAS MADE AS QUICKLY AS POSSIBLE. IN THE ACTIVITY I ALSO NEGLECTED TO FORWARD THE RPT OF TURB ON TO ATC WHICH WAS ALSO MY ERROR.