I like the story of Mr. Fokker himself finding the solution to shooting through a moving propellor. He came up with the idea of an interrupter gear on the machine gun, such that the gun wouldn't fire when the blade was in the way. He drew on a childhood memory of throwing stones between the moving blades of a windmill.

What about those poor buggers who had to go up in the earlier models with metal deflectors bolted to the propellors, and then pound in when they shot the propellor off?