The four blades of this prototype were articulated at the root and were thus able to flap vertically. The original model did not fly, but after various trials and modifications, such as the addition of ailerons on outriggers, the C.4 flew for the first time on 9th January 1923 at Getafe aerodrome on the outskirts of Madrid and covered 183 metres. The autogyro was moved to Cuatro Ventros aerodrome, also in the Madrid neighbourhood, and at the end of the same month performed a closed circuit flight of 4 kilometres in 4 minutes at a height of about 30 metres. Hinged, articulated blades thus proved the answer to the difficulties encountered in the previous types.
P.Lambermont "Helicopters and Autogyros of the World", 1958