No. First: your example in the DC-3 included *feathering*; changing the
AOA to zero.

Ask yourself: how could it make a difference to drag to have such a prop
locked or free to spin?


Alan, look. Feathering an airplane propeller does indeed change the angle
of attack to zero, but that is how you STOP the autorotation. In a boat,
you stop the autorotation by shifting to reverse. The purpose in either case
is the same: to reduce drag.

Your second statement is a non-sequitur. There's no way in the world a
feathered prop CAN spin, right?

Cheers. It's a lively discussion.

Dick