Citation I (C500)
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Workload; Troubleshooting; Human-Machine Interface; Distraction
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Regained Aircraft Control; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Aircraft
Aircraft X was on route from ZZZ1 to ZZZ. While proceeding on the RNAV arrival to ZZZ and just prior to ZZZZZ intersection the aircraft was just leveling off at 20;000 feet when the number 2 inverter failed and the aircraft immediately pitched and rolled the while coupled on the autopilot. We immediately pulled the power back to correct the speed increase and I took the controls; decoupled the autopilot and righted the aircraft returning the aircraft to course and altitude.  During the upset the aircraft lost approximately 1;800 feet and we deviated off the arrival course about 90 degrees. Center inquired as to our status and we advised them that we had an equipment failure and that we had regained control of the aircraft. We also advised that we required no assistance and that we were able to proceed without incident. The corrective action was to switch to the number 1 inverter; re-couple the autopilot once the attitude indicators re-stabilized and to continue the flight normally.  As soon as we were on the ground we advised the company and appropriate corrective action was initiated.
Aircraft X was in route ZZZ1-ZZZ. We were descending on an RNAV arrival; assigned to 20;000 feet. As we were approaching ZZZZZ just prior to level off; we had an inverter failure and autopilot failure. Autopilot failed to capture altitude and deviated from assigned heading. We disconnected autopilot and returned aircraft to assigned flight level and heading.
Citation I flight crew reported an inverter failure caused the autopilot to fail resulting in a temporary loss of control.