Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human-Machine Interface; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude
Air Traffic Control Issued New Clearance; Flight Crew Diverted; Flight Crew Regained Aircraft Control; Flight Crew Landed in Emergency Condition
Aircraft
At cruise at 40;000 feet; 3 hours into our flight between navigation points while scanning the instruments I noticed a flashing 'PITCH' mode annunciation on the PFD (Primary Flight Display). The aircraft then started an uncommanded climb. During this brief time I also saw the standby attitude indicator show red X's on attitude; altitude and airspeed. I told the Pilot in Command 'we are climbing in pitch mode; select vertical speed and recover!' During the altitude recovery the standby altitude showed as high as 47;000 feet then flashed a series of numbers. We never exceeded an actual altitude of more 40;200 feet. Once restabilized at 40;000 feet; the standby attitude; airspeed and altimeter also stabilized but the standby altitude was off as much as 260 feet high.The autopilot changed modes uncommanded from ALT to PITCH and the aircraft started an uncommanded climb. We recovered; called the company and Maintenance. We were then told to divert. We also notified ATC of an avionics issue and that we were diverting for maintenance.
CE680 First Officer reported their aircraft made an uncommanded climb due to the autopilot malfunctioning.