Corradino d’Ascanio's collaboration with Piaggio began in 1931, on the development of a new mechanical component that would revolutionise aviation history. On the variable-pitch propeller, the pitch of the blade can be modified, with electro-mechanical components, in order to obtain maximum yield in a certain speed range: consequently, the engine works constantly at the set speed (cruising speed or maximum speed) and the propeller changes its (angular) speed according to the pitch (a magnitude of distance travelled by a propeller in a rotation). In fixed-pitch propellers, the propeller speed depends only on the number of revolutions of the engine, which entails intervention on the engine speed. With the variable-pitch propeller, control of the aircraft was greatly simplified and use of the engine was more efficient. The great technological innovation represented by this invention meant that demand increased rapidly in the pre-war and war years. Before the outbreak of World War II, in fact, almost all the aircraft produced in Italy were fitted with propellers designed by d'Ascanio, in the various two-blade, three-blade and four-blade versions.