At the beginning of 1922 this prototype with five rigid blades was ready for trial. Though its lateral control was improved, it always showed in the inventor's own words "a tendency to fall over sideways". It was damaged on several occasions and rebuilt four times.
An end was put to La Cierva's failures by a toy autogyro which he had built. Its engine consisted of a twisted rubber band, and its rotary wings of flexible palm wood. Unlike the full-sized machines, it flew properly. On comparing it feature by feature with the C.3, La Cierva discovered that the flexible rotor blades accounted for the toy's successful flight. This gave La Gierva the idea of articulating the blades so as to overcome the unbalance between the advancing and the retreating blade.
P.Lambermont "Helicopters and Autogyros of the World", 1958