Uh, just so those that do not have full feathering props think that they must have one, consider this.  My Hartzell has a maximum coarse pitch setting - I think it is about 40 degrees (I don't have the prop manual handy).  Aerodynamics for Naval Aviators figure 2.19 has chart of propeller blade angle vs change in parasitic drag area.  There is a significant drop in drag area from 12* (flat pitch) to 40* (coarse pitch) and a very small drop if the blade was further pitched at 60*.  There is no further drop from 60* to 90*.  I think we non feathering birds-of-a-feather need some pitch to keep the prop rotating in order to keep the oil pressure high enough to maintain the 40* (duh!).

 

At approximately zero thrust and best glide: cruise pitch = 1500 fpm, coarse pitch = 400-500 fpm.

 

 

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