Caproni Ca . 4 The Caproni Ca . 4 was an Italian heavy bomber of the World War I era . Development . After designing the successful Ca . 3 , Gianni Caproni of the Caproni works designed a much bigger aircraft . It shared the unusual layout of the Caproni Ca . 3 , being a twin - boom aircraft with one pusher engine at the rear of a central nacelle and two tractor engines in front of twin booms , making a push - pull configuration . The twin booms carried a single elevator and three fins . The main landing gear was fixed and consisted of two sets of four wheels each . The most distinguishing feature of the new aircraft was , that it was built in a rare triplane layout , instead of the more common biplane . The huge new bomber was accepted the Italian Army under a military designation Ca . 4 , but it was produced in several variants , differing in factory designations . Description . The Ca . 4 was a three - engine , twin - fuselage triplane of a wooden construction with a fabric - covered frame . An open central nacelle was attached to the undersurface of the center wing . It contained a single pusher engine , pilot , and forward gunner . The remaining engines were tractor mounted at the front of each fuselage . At least one variation of the central nacelle seated the crew in a two - seat tandem format with the forward position a gunner / pilot and the rear position the pilot . Others used a forward gunner with side by side pilot positions to the rear of the gunner . Two rear gunners were positioned one in each boom behind the center wing . An engineer or second pilot could also be accommodated there . Armament consisted of four ( but up to eight ) Revelli 6 . 5 mm or 7 . 7 mm machine gun s in front ring mounting and two boom ring mountings . Bombs were suspended in a bomb bay , which was a long and narrow container fixed to a lower wing . Photographs show at least four different arrangements with regard to the bombing nacelle . Variants . " Note : during the war , all these aircraft were designated Ca . 4 by the Italian Army . At the time , Caproni referred to the various designs by the total power of their engines . After the war , Caproni devised a new designation scheme for their own design — these are used below . " Production figures differ in publications . The most likely number is 38 of all Ca . 4 variants ( other quoted figures are : 38 of Ca . 40 and Ca . 41 and 6 Ca . 42 or 32 Ca . 42 and 21 of other variants ) . Numerous publications incorrectly refer to all variants as the Ca . 42 . Operational history . Ca . 4s were tested by the Italian Air Force in 1917 and began operations in 1918 . They were used for attacking targets in Austria - Hungary . In April 1918 , 6 Ca . 42s were used by the British RNAS ( No . 227 Sqn ) . At least three CA . 42s were sent to the United States for evaluation . After the war , the Ca . 4 was replaced in Italy by the Ca . 36 . Despite its unstable and fragile appearance , the Ca . 4 was well - designed . Its size , without regards to its height , was not any larger than that of other foreign heavy bombers . With Liberty engines , it had a fast speed , similar to other heavy bombers , while its bomb load had one of the largest capacities of that era , surpassed only by that of the Imperial German : Zeppelin - Staaken R . VI . If it had been flown with other engines , its performance would have suffered . A Ca . 48 airliner crashed at Verona , Italy , on 2 August 1919 , during a flight from Venice to Taliedo , Milan , after its wings apparently collapsed in mid - flight at an altitude of 3 , 000 feet ( 912 meters ) . All on board – reported as 14 , 15 , and 17 people by different sources – died . It was Italy ' s first commercial aviation disaster and one of the earliest heavier - than - air airliner disasters .