Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 30; Flight Crew Total 18200; Flight Crew Type 550
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Landed in Emergency Condition; Flight Crew Diverted; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
RUDDER FAIL CAS message followed by dutch roll induced by light turbulence. Unable to maintain altitude or airway. Initially [requested special handling] as dutch roll increased in intensity. Requested block altitude initially; but ATC did not understand this request. Requested lower altitude and descended to FL301.  Was able to stabilize the dutch roll and reconnect autopilot. Followed QRH procedure; but rudder remained completely failed including trim function; discussed options for landing airport and diverted to ZZZZ due to favorable wind conditions and weather. Completed safe landing at ZZZZ about 1:40 after initial event. Flight control computers were operational hydraulics were all operational Remote Electronic Units 15 and 16 were both failed along with Rudder LVDT Disconnect.
Gulfstream G650 Captain reported that Rudder Fail CAS message followed by Dutch Roll required a diversion to a suitable airport.