Technological evolution
Aerial propellers

The propeller has always benefited from the technological advances generated by the growth of aeronautics; in particular, it has continually adopted the best materials on offer at the time: first wood, then metal (mechanically welded steel, solid aluminum alloy) and, finally, composite materials (the propeller is, in this respect, one of the few applications to use these materials for equipment that is structurally vital to the aircraft).

With regard to the evolution of hub technologies, it should be noted that at first, the hub was either non-existent (the propeller being a single-piece unit directly attached to the motor shaft), or only served as a mounting point for the blades; later, a two-position pneumatic pitch change (which could only be activated once during flight) was invented. This principle of changing blade pitch during flight has been adopted by all...