In the PT6 the Power lever sets the speeder spring in the FCU. Fuel is added or reduced to hold the N1 at requested RPM.
Correct,
rigpiggy, and congratulations, you are one of a very limited number of pilots that know this.
The question of what the power lever does is a very, very fundamental thing about the PT6 engine and the single fact that promotes the most complete understanding of the operation of the engine.
The power lever does not control fuel flow. It does not control ITT. It does not control torque.
It controls Ng (aka N
1) speed, via a speeder spring / flyweight mechanism, known as the "Ng governor".
When the pilot positions the power lever to a particular setting, he is in fact commanding a particular Ng value. The Ng governor will then increase or decrease the fuel flow so as to bring the Ng speed to equal the speed commanded by the power lever position.
With those variations to the fuel flow, of course, you will get variations to the ITT and torque (and prop RPM too, if not yet in the governing range).