The ground attack bomber my dad flew in in WWII was the forgotten Lockheed PV1 Ventura and one of its' significant features was the installation of full feathering three bladed props like that one. He told a story about a challenge that developed between his aircrew and a group of P51 pilots over fighting superiority of their respective aircraft and they agreed to stage a mock battle and see who could get who in their gun cameras. He said on the first attack as the 51s were descending at them his pilot put it into a steep dive to gain airspeed, then as they were about to be overtaken he turned the props fully flat and the plane almost stopped midair causing the 51s to overtake so rapidly that they couldn't aim in time and he then resumed normal thrust and they got 3 of the 4 in their first pass and the remaining one the same way in the next pass. He said full feathering those big props was like putting a couple of 10' diameter plywood discs into the airstream.