as
tu114 said, if the pitch is too coarse the blades will stall and just stir a big disc of air around.......
but, because the tip of the blade travels much faster than the root of the blade, a twist is built into it.....therefore the angle of attack varies along the blade-length.
if you imagine blades with
notwist and aligned with their chords parallel to the shaft.......it would be a paddle wheel with zero thrust, would it not?
in summary,what theysaid,- YES
