Small Transport; Low Wing; 2 Turboprop Eng
Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 60; Flight Crew Total 18000; Flight Crew Type 75
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Ground Strike - Aircraft; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Taxiway
Aircraft Aircraft Damaged
Aircraft
After landing; contacted Ground and was given instructions. After taxiing for about 3000 feet I was getting ready to turn right into the FBO. The aircraft suddenly made a hard 90 degree left turn; exited the taxiway into the grass where the nose gear sheared off. The nose gear shearing off caused both props to strike the grass.  After talking with the A&P who maintains the aircraft; he described the operation of the connection of rudder pedals to the nose gear. His best guess; without examination; is that the hollow tube may have been corroded and when retracting gear on takeoff the tube may have partially failed. Turning on the taxiways may have caused complete failure.
Small transport pilot reported the aircraft made a sharp uncommanded turn off the taxiway; resulting in nose gear failure and prop strike.