Caproni Ca . 165 The Caproni Ca . 165 was an Italian biplane fighter developed just before World War II , but only produced as a prototype , as the competing Fiat CR . 42 " Falco " was selected for series production . Design . Even if known for three - engine heavy bomber s , Caproni had a long history with fighters , started in 1914 with an interceptor with a single machine gun and a monoplane . This was innovative for its time , but it had also no success , as 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 . Testing and evaluation . At Guidonia , the aircraft was tested like the many other fighters present for evaluation . However , it was only tested against the Fiat CR . 42 " Falco " , the only other biplane . In mock - up fights the Ca . 165 outperformed the CR . 42 , thanks to the superior aerodynamics and available power . Despite this , the aircraft was rated inferior as the CR . 42 was more maneuverable and employed a reliable powerplant while the Caproni engine was experimental and had poor reliability . However , the Ca . 165 was declared the " winner " of the mock fights , so General Valle ordered 12 examples on 2 September 1939 , although the order was cancelled on 11 October 1939 and changed to 12 Caproni F . 5s . This production shift was made even though it involved the payment of a penalty . The Ca . 165 was comparable in useful load ( 570 kg / 1 , 257 lb vs . 575 kg / 1 , 268 lb ) and weapons ( 2 × 12 . 7 mm / 0 . 5 in , 1 × 7 . 7 mm / 0 . 303 in ) to the CR . 42 , but it was 200 kg ( 441 lb ) heavier with less wing surface , so it had wing loading of 113 kg / m compared to 99 for the CR . 42 ; and that , coupled with the less effective controls , made the Ca . 165 less agile . Despite these shortcomings , the Ca . 165 ' s minimum speed was lower ( 114 km / h / 71 mph vs 122 km / h / 76 mph ) , allowing for shorter takeoff runs and slightly better low - speed performance . The Ca . 165 had a very slim and small fuselage , but was heavier than the CR . 42 , which was due , arguably , to the different engine and construction . The Caproni was not really a ' turning fighter ' , but given the limits of biplanes , was more of an ' energy fighter ' with more pronounced capabilities in speed than turning ( as was emphasized by the test pilots ) . An improved version was designed to address the maneuverability limitations , but the development was interrupted . It was built with non - strategic materials ( steel and wood mainly ) , so it could have been an advantage in the war in terms of strain on the materials industry , but given the type of engine , it is unclear if it was an economically practical aircraft . Caproni tried other ways to improve this powerful biplane , first with the 746 kW ( 1 , 000 hp ) Piaggio P . XI radial engine , then with a 746 kW ( 1 , 000 hp ) Isotta Fraschini L . 170 liquid cooled powerplant , and the redesigned sesquiplane wings as the Ca . 173 . None of these proposals were successful , at least not enough to pique the interest of the " Regia Aeronautica " . In any case , both engines were far from being sufficiently reliable and were never adopted in large numbers by the Italian air force . Cancellation . Perhaps the influence of Fiat contributed to the selection of the CR . 42 " Falco " over the Ca . 165 , although Caproni was an influential company itself at the time . Apparently the bottom line was that the Ca . 165 ' s engine was much less reliable and only 44 kW ( 60 hp ) more powerful , while the aircraft itself was 200 kg ( 440 lb ) heavier . The Ca . 165 , despite being considered the winner in the mock - up fights , lost the final evaluation . Apparently , test pilots flying the Ca . 165 managed to outperform the " Falco " but disliked the aircraft itself . The faster speed was a more modern concept for a new generation fighter ( especially in the interception of fast bombers such as the Bristol Blenheim , which often proved too fast for the " Falco " ) , and speed was an increasingly important design consideration in World War II - era aircraft . The engine ' s poor reliability was also apparent , and when considering which aircraft to produce , this could have been a disadvantage as well . In any case , the Ca . 165 was produced in only a single prototype and so vanished from history ; instead the Fiat CR . 42 became the most produced Italian fighter , despite its overall obsolescence , with almost 1 , 800 examples built until 1944 .