SA-227 AC Metro III
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Situational Awareness
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Loss Of Aircraft Control; Ground Event / Encounter Object; Ground Excursion Runway
Aircraft Aircraft Damaged
Aircraft; Human Factors
My nose wheel steering was deferred. I taxied to the runway using differential power and braking. I started to execute a normal takeoff and something didn't feel right with the power. I can't describe it but it just didn't feel right. I aborted the take off. I had aborted before getting a good look at the engines. I pulled off the taxiway and in the run-up area and brought the power up to see if I could recreate the issue while not moving. The engines proceeded to run fine. I then notified Tower that I was ready to try to takeoff again. I started to execute the takeoff and noticed it was pulling to the left. I started to add left power until I could hold as straight as I could. I looked down at the torque gauges and saw I had a significant amount of differential power (left engine was at 80-90 and the right was down at 20.) I immediately executed a second abort. This time the plane went hard over to the left; skidded on the runway; and then went into the grass; taking out a taxiway sign. I immediately shut both the engines down and ATC sent the response team.I think I would've been able to keep the airplane on the runway if the nose wheel steering wasn't deferred. It had been worked on in the past week and the mechanic deferred it after replacing some parts.
SA227 Captain reported a runway excursion resulted when directional control was lost due to low torque on the right engine and deferred nose wheel steering.