BE200 PILOT REPORTS UPSET IN NIGHT IMC WHEN ADI FAILS AT FL230. SINGLE PILOT RECOVERS WHEN PASSING INTO VMC AT 13000 FEET.

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DEPARTED ZZZ1; WX WAS VMC. CLRED DIRECT ZZZ AND A CLB TO FL230. AUTOPLT ENGAGED AT CRUISE ALT. THERE WAS LIGHT PRECIP; CLOUD DECK RIGHT BELOW ME. ENG ANTI-ICE ON; WINDSHIELD HEAT ON; PROP ANTI-ICE ON; WINGS WERE CLR. APPROX 160 NM E OF ZZZ THE PLT'S ADI ROLLED ABRUPTLY TO THE L AND PITCHED DOWN; IT STAYED LOCKED IN THIS POS. THE AUTOPLT FOLLOWED IMMEDIATELY AND I WAS IN AN UNKNOWN ATTITUDE IN NIGHT IMC. THE AUTOPLT DISC LIGHT ILLUMINATED AND THE COPLT'S ADI LOCKED UP; AS WELL. I ATTEMPTED TO RECOVER USING AIRSPD INDICATOR; VVI; HSI AND ALTIMETER. THE ACFT WENT THROUGH SEVERAL GYRATIONS: AIRSPD RANGED FROM THE BARBER POLE TO APPROX 150 KTS. PITCH/ROLL ATTITUDE WAS UNKNOWN. STRONG POSITIVE AND NEGATIVE G-FORCES WERE EXPERIENCED. I BROKE OUT OF THE CLOUDS AT APPROX 13000 FT MSL AND WAS ABLE TO ORIENT MYSELF USING GND LIGHTS. I WAS ABLE TO STABILIZE THE ACFT AT 180 KTS. AFTER CHKING ENG INSTS (ALL OK); WARNING LIGHTS (AUTOPLT DISC) AND CIRCUIT BREAKERS (ALL IN); I REQUESTED AND RECEIVED CLRNC DIRECT ZZZ1 AT 9000 FT MSL. THE APCH AND LNDG (NIGHT VMC); A VISUAL STRAIGHT-IN WAS UNEVENTFUL. I BELIEVE THIS INCIDENCE WAS CAUSED BY A MECHANICAL FAILURE OF THE PRIMARY FLT ADI; HOWEVER; THIS UNFORESEEN FAILURE SERVES TO EMPHASIZE THE IMPORTANCE OF SINGLE-PLT/CREW TRAINING TO INCLUDE UNUSUAL ATTITUDE RECOVERY WITHOUT AN OPERATIVE ADI AND CROSS-COCKPIT INST USAGE FOR RECOVERIES. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER BELIEVES THAT HAD HE QUICKLY TRANSFERRED HIS SCAN TO COPLT'S ADI; HE COULD HAVE RECOVERED EASILY. BY THE TIME THE THOUGHT OCCURRED; THAT ADI HAD FAILED ALSO; LEAVING ONLY NEEDLE; BALL; AND AIRSPEED. THE ACFT'S OPERATOR PLANS TO INSTALL A STANDBY ADI IN THE NEAR FUTURE.