Rotor blades are twisted, and for the same reason as propellers.
Propellers autorotate; ever tried restarting an engine in a twin engined aeroplane ?
The differences between propellers and rotors exist because they are optimised for different purposes, but their modus operandi and basic function are the same, ie chucking air from above the blade to below.
Last edited by puntosaurus; 14th October 2009 at 21:42.