Caproni Ca.73

Caproni
Industry	Aerospace, Aircraft manufacturing
Founded	1908
Founder	Giovanni Battista Caproni
Headquarters	Italy
Products	Aircraft (including Caproni Ca.73)

Template:Infobox aircraft

The Caproni Ca.73 was an inverted sesquiplane crafted by the Italian aircraft company Caproni.

Initially intended for civilian use, it completed its maiden flight in 1925 and entered service as an airliner accommodating up to 10 passengers simultaneously. Subsequently, the aircraft was repurposed for military application when the newly established Regia Aeronautica required a more advanced light bomber to supersede its outdated First World War fleet. Modifications were made to equip it with several defensive machine guns and bomb-carrying capabilities. The Ca.73 remained active in frontline military roles through the mid-1930s.

Design and development

The Caproni Ca.73 featured an inverted sesquiplane layout with a biplane tail assembly, a rigid central wing section, and two engines arranged in a push-pull configuration housed within a single nacelle. This nacelle was affixed on struts located in the interplane gap above the fuselage. The fuselage itself was positioned entirely beneath the lower wing, a design choice that enhanced safety during landings and provided notable buoyancy in water ditching scenarios. To support such operations, the fuselage base was reinforced significantly.^[1]

In its airliner setup, the fuselage interior included two pilot seats arranged side-by-side and space for ten passengers seated in two rows separated by a central aisle.^[1] Besides passenger transport, it could carry up to 300 lb of baggage or air mail. The military adaptation closely resembled the commercial version but replaced passenger accommodations with various armaments.^[2] Defensive weaponry consisted of three machine guns: one positioned at the bow, another behind the wing cell, and a third mounted underneath it. These guns’ firing arcs overlapped to ensure comprehensive coverage of all surrounding airspace.^[3] Bomb payload capacity reached 1,000 kg (2,205 lb.), with bombs strategically placed near the aircraft's centre of gravity.^[3]

Power was typically supplied by two Isotta Fraschini Asso 500 engines, each delivering up to 500 hp. These were installed in tandem within a shared nacelle mounted on struts between the wings above the fuselage, creating a robust yet straightforward central structure.^[1] The oil reservoir was situated between the engines, while fuel tanks were embedded within the lower wing. Fuel was transferred from these tanks by dual windmill pumps into two gravity-fed tanks located in the upper wing, from which both engines drew fuel.^[1]

Regarding flight performance, this aircraft was regarded as relatively straightforward to handle, featuring controls that were both responsive and light—achieved through careful balancing of the ailerons and rudder.^[1] It exhibited stable handling characteristics and maintained control even if one engine failed mid-flight. Moreover, with a payload up to 1,500 kg (3,307 lb.), it could sustain an altitude of 1,000 m (3,280 ft.) on a single engine.^[4] Its climb capability was considered strong for its time: carrying a useful load of 2,300 kg (5,070 lb.), it could reach altitudes of 1,000 m in seven minutes; 2,000 m in fourteen and a half minutes; 3,000 m in twenty-three minutes; 4,000 m in thirty-seven minutes; and 5,000 m within sixty-six minutes.^[3]

Operational history

The release of General Giulio Douhet's influential work on strategic bombing, Il dominio dell'aria (The Command of the Air), in 1921, made Italy's military strategists keenly aware of their deficiency in this domain. Founded as an independent branch in 1923, the Regia Aeronautica initially operated Caproni Ca.3 bombers dating from the First World War, prompting an urgent search for a modern replacement. As an interim measure, the existing Ca.73 was adapted into a combat aircraft by installing gunner stations at the nose, dorsal, and ventral mid-fuselage positions. Bombs were mounted externally on racks attached to the sides of the fuselage.

By 1931, the Ca.73 and its enhanced variant, the Ca.74, formed the core of the night bomber fleet within the Regia Aeronautica. This model remained active in frontline roles until 1934 and was involved in Italy's military campaigns in North Africa starting from 1926.

Variants

File:Caproni Ca.73 bomber left side photo NACA Aircraft Circular 51.jpg

Caproni Ca.73ter bomber image from NACA Aircraft Circular 51

Ca.73 – commercial airliner equipped with Isotta Fraschini Asso 500 powerplants
- Ca.73bis – airliner variant powered by Lorraine-Dietrich engines
- Ca.73ter (later renamed Ca.82) – bomber configuration featuring gunner stations and fuselage-mounted bomb racks
- Ca.73quarter (subsequently called Ca.88) – bomber with updated control mechanisms and reinforced structural elements
  - Ca.73quarterG (later designated Ca.89) – bomber incorporating a glazed nose, bomb racks beneath the wings, and a retractable ventral gun turret
- Ca.74 (later redesignated as Ca.80) – model powered by Bristol Jupiter engines
Ca.80 – new designation for the Ca.74
- Ca.80S – specialized version for air ambulance services and paratrooper transport
Ca.82 – new name for the former Ca.73ter
Ca.87 – modified for long-range record attempts (single conversion)
Ca.88 – new title for the former Ca.73quarter
Ca.89 – new designation for the previous Ca.73quarterG