What happens when changing the throttle on a PT-6 engine?
Pushing the power lever forward will command more power. Fuel flow will increase, so will the TIT and torque.


To maintain the same RPM, more torque is needed as the prop blades will increase their angle.


Pulling all the way back does not cut the fuel flow (FF). The minimum FF required to sustain operation will be managed by the fuel control unit (FCU).


Sidenote on terminology: throttle, power, and thrust levers are the controls for piston, turbine, and jet engines respectively.




RE: Torque limits

It depends on the engine, but generally:


  In cold weather conditions, torque limits can be exceeded while temperature limits are still within acceptable range. While in hot weather conditions, temperature limits may be exceeded without exceeding torque limits. In any weather, the maximum power setting of a turbine engine is usually obtained with the throttles positioned somewhat aft of the full forward position.




Related: Is turboshaft fuel efficiency affected by N2 loading?