As De la Cierva's autogyros achieved success and acceptance, others began to follow and with them came further innovation. Most important was the development of direct rotor control through cyclic pitch variation, achieved initially by tilting the rotor hub and subsequently by Raoul Hafner by the application of a spider mechanism that acted directly on each rotor blade. The first production direct control autogyro was the C.30, produced in quantity by Avro, Liore et Olivier, and Focke-Wulf. This machine allowed for change of motion in any direction - upwards, downwards or sideways - by the tilting of the horizontal rotors and also effected a minimising of some of controls used in more conventional aircraft of the period. Development of cyclic pitch variation was also influenced by the Dutch helicopter pioneer Albert Gillis von Baumhauer, who adopted swashplate principle in his designs and probably influenced Cierva in their meeting in 1928.
