Golden Eagle 421
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Total 6500; Flight Crew Type 140
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew FLC Overrode Automation; Flight Crew Overcame Equipment Problem; Flight Crew Regained Aircraft Control
Aircraft
Level in cruise flight the aircraft started to oscillate. I decide to disconnect the autopilot and hand fly. After disconnecting the autopilot at some point notice the pitch trim running away nose up. I was fumbling looking for the pitch trim circuit breaker and trying to fly the airplane. This was the first time I had flown this particular aircraft and the autopilot configuration was different from other 421's I currently fly. Eventually the control forces became too strong to maintain good control of the aircraft. I had entered a descent with the spoilers extended to maintain control and killed all avionics power in an effort to take power from pitch trim actuator. I had another pilot with me which was helping; at some point we got the aircraft trimmed up manually. Pulled the circuit breaker and then turned on avionics bus back on and established communications with ATC. Decided not to declare an emergency only because he had gained control and were in normal operations after that point. We were a few minutes away from ZZZ and had regained control of the aircraft. Made and uneventful landing ZZZ to ops-check the trim and autopilot system.
C421 Captain reported a runaway pitch trim system during cruise. Captain disconnected the autopilot; regained control of the aircraft and landed at the nearest suitable airport.