The Caproni Ca.165 was an Italian biplane fighter developed just before World War II, but produced only as a prototype, as the competing Fiat CR.42 Falco was selected for series production.
Although known for three-engine heavy bombers, Caproni had a long history with fighters, starting in 1914 with an interceptor monoplane with a single machine gun, and a monoplane.
This was innovative for its time, but it had also no success, as had almost all the fighters proposed in the next decades.
Many types of machines were developed by Italian industries prior to World War II, and some were produced at least in limited numbers, but this would not be the case with the Ca.165, a biplane fighter proposed for a fighter contest.
In February 1938, it flew for the first time as prototype.
The Ca.165 had a mixed construction.
The fuselage was framed in steel with a skin of light alloys, while the wing was built out of wood with fabric skin.
Finally, the tail was metallic, also covered in fabric.
The Ca.165 had a narrow fuselage featuring an enclosed cockpit.
The undercarriage was fixed with spatted wheels.
A unique feature of the Ca.165 was the retractable radiator, which the pilot could deploy for optimum performance, or retract depending on the flight conditions: completely open in climbs, or closed in level flight and dives.
In this way, it was similar to the Morane-Saulnier M.S.406.
When deployed, the radiator significantly increased the drag on the aircraft, but increased engine performance and reliability.
The engine was a V-12 671 kW (900 hp) Isotta Fraschini L.121 R.C.40 driving a three-bladed Alfa Romeo electric propeller.
Top speed was around 465 km/h (289 mph) at 5,350 m (17,550 ft) with a 10,000 m (32,810 ft) ceiling.
The range was relatively small, around 672 km (418 mi). Dimensions were 8.1 m (26.6 ft) length, 9.3 m (30.5 ft) height, 2.8 m (9.2 ft) wingspan, 21.4 m2 (230.3 ft2) wing surface.
The weight was 1,855/2,435 kg (4,090/5,368 lb), with 570 kg ( lb) of payload.
After several modifications, the Ca.165 had the tail surface augmented and the aft fuselage lowered to fit a canopy with 360° visibility.