SA-227 AC Metro III
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Ground Strike - Aircraft; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway
Aircraft Aircraft Damaged; Flight Crew Rejected Takeoff; General Maintenance Action
Aircraft
When attempting to set takeoff power the left engine did not produce more than 25-30% torque. After verifying that this was not due to a momentary lag of torque; which I have experienced on many Metro engines/takeoffs; the takeoff was aborted however the plane was heading to the left of center line due to the higher torque achieved by the right engine. When the power levers were brought to idle the plane straightened down the runway to the left of the center line. The nose wheel steering button on the power lever was being pushed but either it was not working or was not effective enough to turn the plane back toward the center line. I verified with my left thumb and finger that the nose wheel steering switch was in the armed position and also pressed the 'park' steering function for additional turning help. When I (quickly) recognized that wasn't working left power was applied with the hope that there would be some power and right brake was applied to try to turn the plane to the right however; it didn't work and instead the plane started turning to the left and exited the runway where the plane stopped and was shutdown. After shutdown it was observed that a left propeller tip hit a runway edge light.
SA-227 Metro III Captain reported rejected takeoff due to loss of torque on one engine resulting in a loss of directional control; and a runway excursion.