Ok now,
another interrogation :
If Bęta is the range where the power lever directly acts on the prop speed.. ok, so:
When you're applying your power on brake before take off, the prop lever is full forward for full fine, so, before the prop is reaching the 2000-2200 RPM, the blade rests on the low pitch mechanical stops ( before the CSU regulate the RPM by increasing pitch to maintain the selected RPM ). So here you are in Bęta range ?
But what about the blade pitch coming near to 0°, to produce zero thrust ?
As I wrote earlier in this thread, in the PC6 you enter into Bęta range by pulling power lever all the way back against idle stop, and you actually control the Np with the prop lever. Is this particular to PC-6, which carry PT6A-27 or -34, or it's same with your Twin Otter ?
Thanks