One of Italy’s oldest flying schools, the Scuola di Aviazione Caproni was located at Vizzola Ticino near Varese. In the mid 1930’s, the school was modernized and expanded to a point that they could undertake production of components for other elements of the Caproni aircraft empire as well as continuing as a flying school. In 1937 this expansion program reached the stage that a design department was established under Ing. Fabrizi.

The organization’s first design was extremely ambitious – a modern interceptor fighter that was schemed in both inline and radial engine forms as the F.4 and F.5 respectively. The airframe was common to both except for the forward fuselage sections where changes were required for the different engines, and was of mixed wood and metal construction. The core of the structure was the fuselage that was of oval section and based on welded steel tube primary structure covered with Dural skin. The flying surface consisted of a Dural constructed tail unit with metal skinned fixed surfaces and fabric covered moving surfaces and a cantilever low set wing. The wing was of wooden construction with stressed plywood skinning and a slightly unusual planform with a curved leading edge and straight trailing edge. The two wing halves were attached at a slight dihedral angle to the stub roots built integral with the central fuselage section. The wings were tapered in thickness and chord and carried the standard trailing edge combination of outboard ailerons and inboard flaps. The airframe was completed with a high-set fully enclosed cockpit and the tailwheel landing gear with wide track main units.

The F.4 was to be powered by a 960 hp Isotta-Fraschini Asso 121 RC.40 Vee engine, but late in construction it was decided to replace that with a 1,175 hp Daimler Benz DB601A. This change delayed the F.4’s completion into 1940, but flight trials revealed the F.4 to possess good performance, excellent maneuverability and first class handling characteristics. No production followed however, for it was determined to terminate development of the F.4 for the F.6, essentially an F.4 powered by a 1,475 hp Fiat RA.1050 RC.58 Tifone, the license built Daimler Benz DB 605A.

The delay meant that the F.5 was the first of Fabrizi’s related fighter designs to fly, an event that took place in early 1939. The F.5 was powered by a Fiat A.74 RC.38 radial engine in a trim circular cowling that fitted so closely around the cylinder heads that bulged fairings were necessary to accommodate the rocker arms. By Italian standards of the period, the F.5 was an advanced fighter. The prototype was followed by 14 production aircraft. The production aircraft were changed using a revised and enlarged vertical tail surface to provide better directional stability, provision for an auxiliary fuel tank in the rear fuselage, an altered cockpit canopy and a non-retractable tailwheel. No further production followed.

The fighters were assigned to the 51st Stormo and the 8th Brigata Caccia Terrestre for the defense of Rome, first as night fighters and then as day fighters.

Article by JDG

Sources:
Wings: London Blitz to Pearl Harbor.
Elke Weale, Combat Aircraft of World War II, Bracken Books, 1985.