Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance
Flight Crew Landed in Emergency Condition; General Maintenance Action
Aircraft
Enroute to ZZZ1 from ZZZ started to experience power surges on the engine when I was in the cruise phase of flight. Without manipulation of the power control lever the engine would surge from about 900 foot pounds of torque up to 1800 foot pounds of torque. The power surges were continuous and could not be controlled with the control power lever. When I landed I still had 600 foot pounds of torque at an idle power setting and landed the aircraft safely at 120 kts with 10 degrees of flaps.Unknown. Maintenance is still looking into the matter and trying to figure out what the cause of the power surges. Director of safety is looking at the video footage of the flight.My reaction was to trouble shoot the situation. When the power surges were consistent; I decided to divert back to ZZZ. At that point I did not declare an emergency as I was still trouble shooting by manipulating the power control lever and seeing how the engine would react. While enroute to ZZZ I inquired to ATC about the weather at the field as I remembered the field went IFR after I departed. Sure enough the field was IFR and I did not want to try to shoot an ILS while dealing with a loss of control of power management. At that point I decided it was the right thing to advise ATC as I could not control the power surges of the engine and divert to ZZZ2 where it was clear VFR weather with calm winds. ATC asked which runway I would like. I picked Runway XX since I was on a westerly heading and had the field in sight and the winds were calm. I did land the aircraft at a higher than normal landing speed but was still able to land safely with using about half of the runway.
C-208B Captain reported engine surges resulted in diversion to VFR airport.