Mm ok.. !!
In the PC-6, the power lever require to be lifted to pass over the idle gate ( to enter into reverse ).
So, there is two ranges, ALPHA is all the range the FCU, CSU etc are managing when the power lever is from IDLE to Full power, then when you go into the reverse position, it incluede the Beta range.. is it that ?
So Beta is reached by lifting the lever, and going a but aftward, not fully because it will be reverse..
All is way more clearer now !
If some PC6 pilot could come and confirm that