SA-227 AC Metro III
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Loss Of Aircraft Control
Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
When trying to level off at 3;000 ft. the trim became stuck. I proceeded to pull back power and even with doing that and being in an almost standing position with all my weight down the plane was continuing to climb I tried switching it to the opposite side trim using aux trim it was still stuck. I advised ATC. At this point my arms are starting to get tired I tried flipping the trim again to reset it. I get the trim back for maybe 20 seconds but then it freezes again at this point the plane is controllable enough to maintain altitude though I'm using a lot more muscle then usual I tell Control I need to go back to ZZZZ; ZZZZ1 airport is short and has a steep descent and ZZZZ2 is too far and I'm not sure my arms would hold out that long for the longer runway and more services. I run the QRH which reading the notes I bring flaps and gear in earlier to make the plane more controllable and land.Trim motor bad.Called Dispatch; Maintenance Control. Also filled out paperwork with ZZZZ airport and called their Tower.I think memory items should include stuck trim; we have runaway but that checklist doesn't go over using flaps and gear to help you out and though once I had a second to think it made sense when you're using all your muscles to try and keep the plane from becoming uncontrollable you become very focused on just that aspect.
SA-227 Captain reported a failed elevator trim system resulted in a return to the departure airport.