Caproni Ca . 3 The Caproni Ca . 3 was an Italian heavy bomber of World War I and the post - war era . It was the definitive version of the series of aircraft that began with the Caproni Ca . 1 in 1914 . Development . The development of the Ca . 1 to the Ca . 2 suggested the benefits of increasing amounts of power to the very sound airframe . The Ca . 3 was a development of Ca . 2 , by replacing the two engines mounted on the booms with the same Isotta - Fraschini engine that had been used as the central , pusher engine on that design . The prototype flew in late 1916 and was soon put into production . Known to Caproni at the time as the Caproni 450 hp , the Italian Army designated it the Ca . 3 . In Caproni ' s post - war redesignation , it became the Ca . 33 . Somewhere between 250 and 300 of these aircraft were built , supplying the Italian Army and Navy ( the latter using the type as a torpedo bomber ) , and the French Army . Late in the war , Robert Esnault - Pelterie built the type under licence in France , building an additional 83 ( some sources say only 19 ) aircraft . " Note : there is some variation in published sources over early Caproni designations . The confusion stems , in part , from three separate schemes used to designate these aircraft - Caproni ' s in - house designations of the time , those used by the Italian Army , and designations created after the war by Caproni to refer to past designs . " Description . The Ca . 3 was a three - engined biplane of wooden construction , with a fabric - covered frame . The crew of four was placed in an open central nacelle ( front gunner , two pilots and rear gunner - mechanic ) . The rear gunner manned upper machine gun s , standing upon the central engine in a protective " cage " , just in front of a propeller . The fixed conventional undercarriage had double main wheels under each engine and a tailskid under the extreme tail of each boom . A substantial double nosewheel prevented damaging and dangerous noseovers . Armament consisted of two to four Revelli 6 . 5 mm or 7 . 7 mm machine guns , one in front ring mounting and one , two or sometimes even three in an upper ring mounting . Bombs were suspended under the hull . Operational history . The Ca . 1 entered service with the Italian Army in the middle of 1915 and first saw action on 20 August 1915 , attacking the Austrian air base at Aisovizza . 15 bomber squadrons ( 1 - 15 " Squadriglia " ) were eventually equipped with Ca . 1 , Ca . 2 , and Ca . 3 bombers , mostly bombing targets in Austro - Hungary . The 12th squadron operated in Libya . In 1918 , three squadrons ( 3 , 14 and 15 ) operated in France . Apart from the Italian Army , Caproni Ca . 3s were also used in British squadrons , before the introduction of the Handley Page Type O bombers . Original and licence - built ones were used by France ( original Caproni were used in French CAP " escadres " , licence - built examples in CEP " escadres " ) . They were also used by the American Expeditionary Force . Some of the Ca . 36Ms supplied after the war were still in service long enough to see action in Benito Mussolini ' s first assaults on North Africa . This plane is also remembered for a tragedy on May 4 , 1919 , which killed the French General Dr . Milan Rastislav Stefanik , who was the minister of war in the Czechoslovak Republic at the time . The accident occurred at the conclusion of a flight to Campo Formido near Udine to Bratislava ( capital of Slovakia ) . On his initial approach , the pilot determined that the ground was too wet to land on , so he increased power to the engines and began to aim the plane to a landing patch further afield which appeared to be dry . While doing so , one of the engines exploded , causing the aircraft to nosedive . General Stefanik and the three Italian crew members were pronounced dead at the scene . A subsequent investigation determined that the most likely cause of engine failure was due to a failure of the air blast cooling of the engine , probably induced by the increased strain cause by the pilot ' s sudden demands on the engine after the aborted landing . There were allegations that a Czech anti - aircraft artillery company had fired on the craft , either because they mistook the plane ' s Italian markings for Hungarian markings or that they had done so as part of a conspiracy to see Gen . Stefanik killed in order to prevent him from putting forth proposed changes in the Czech government . These allegations were never proven , and the failure of the engine ' s blast cooling is widely accepted as the best explanation for the accident . Variants . " All of the following designations were applied after the war . At the time , all were known as the 300 hp by Caproni and the Ca . 3 by the Army . "