Hi everyone, could someone please explain what beta range is?
Its the angle that the prop blades get moved to, it is prop dependent and goes from forward thrust to negative values for reverse thrust. Different props on the same engine have different values. To the pilot there isn't much difference because it is a range which is normally protected on the power levers and its always protected if it is fatal going into it in the air. There are some types which will allow you to selected it in air.
Does the beta range differ between engines and if so why
the beta range itself doesn't really change apart from the angles the blades work between. The differences in engines are to do with how they are designed. PT6's are a free turbine and do it differently to a Garrett which is a direct shaft engine.
Also how does the reverse torque (thrust) on at turboprop work to slow down the aircraft?
Exactly the same as normal thrust. The prop moves a mass of air towards the rear of the aircraft to produces forward thrust. And because the blade angle as been altered to push air towards the front of the aircraft it produces reverse thrust.