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 guns 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.
 * 1. No nacelle - presumably not a combat configuration.
 * 2. A tall, narrow nacelle that housed approximately 12 internal bombs vertically and another 18–20 strapped to the outside.
 * 3. A shorter nacelle that may be the lower half of the tall nacelle but with no external bombs.
 * 4. No nacelle but with a single long bomb/torpedo slung under the bottom wing.

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.''
 * Caproni Ca.40 - single prototype.
 * Caproni Ca.41 - production variant, essentially similar to the prototype and powered by 3 Fiat A.12 inline engines of 210 kW (280 hp). A few Ca.41s were powered by 186 kW (250 hp) Isotta Fraschini engines instead. These were referred to internally by Caproni as the Caproni 750 hp. A total of 41 were built.
 * Caproni Ca.42 - powered by Liberty 298 kW (400 hp) inline engines and known internally as the Caproni 1,200 hp. Twelve built.
 * Caproni Ca.43 - single example of a floatplane variant.
 * Caproni Ca.48 - Airliners converted from Ca.42s after World War I; the Ca.48 first flew in 1919. The double-deck passenger cabin mounted between the booms seated a total of 23 passengers who entered via the nose nacelle; 16 of them sat in the lower cabin on long benches alongside its walls with large windows providing them with good views, and the other seven passengers sat on an upper deck, as did the pilots. The Ca.48 was powered by three 298-kilowatt (400-horsepower) Liberty L-12 engines. Although it is unlikely that the Ca.48 ever entered airline service, a Ca.48 did visit the First Aviation Exhibition Amsterdam of August–September 1919, where it was very popular with visitors, among whom was Prince Hendrick (1876–1934), Prince Consort of the Netherlands (1901–1934).
 * Caproni Ca.51 - single example of a considerably enlarged design with biplane tail and tail barbette. Three × 522 kW (700 hp) Fiat A.14 engines.
 * Caproni Ca.52 - Ca.42s built for the RNAS. Six built.
 * Caproni Ca.58 - Ca.48s re-engined with Fiat A.14 or Isotta Fraschini V.6.
 * Caproni Ca.59 - as for the Ca.58, but this designation used for customers outside Italy.

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.

Operators

 * 🇮🇹 Italy : Corpo Aeronautico Militare
 * UK
 * 🇺🇸 USA

Video

 * Film footage of Caproni Ca.42