RE: in-flight variable pitch prop
There used to be a whole list of props at one time. Different shapes, diameters and spinners. The largest being a 12"
Now if this set up was modified with carbon blades with dovetailed hubs ends I think it could be done for larger engines. But what's the point? How many will you sell and how many people would sue you if something breaks after it was involved in a crash or prop strike?