Two prototypes were ordered by the Air Force from Fiat and these became "MM.1" and "MM.2". They were largely copies of one another save for a change to the rudder unit and the model of Hispano-Suiza engine fitted. The evaluation phase allowed the Fiat product to showcase its considerable handling, maneuverability, and straight-line speed to the point that Air Force officials were suitably impressed. The aircraft won out over a competing design from SIAI (the model S.52).
The prototype was finalized into the "CR.1" (carrying the initials of engineer Celestino Rosatelli / Casia Rosatlli) and this differed by using a smaller-area wing structure along with a new engine cowling fitting a revised radiator unit. An initial order of 100 aircraft were charged to the Fiat factory and these were produced from 1924 to 1925. In 1925, SIAI contributed 100 more aircraft and, from 1925 to 1926, forty more examples followed from Meridionali (OFM of Napoli) for a grand total of 240.
The initial Italian squadron to equip with the type was 1st Fighter Group and a dozen total squadrons were eventually arranged to field the new fighter by the middle of the decade. Latvia became the only foreign customer of the product while Belgium and Poland were interested enough in it to hold formal evaluations (neither would adopt it). Latvia ordered nine aircraft for service with its Air Force and Navy and these carried Hispano-Suiza HS8N8 series engines of 300 horsepower. The fleet would serve until 1936.
By the 1930s, the Italian models themselves were re-engined with Isotta-Fraschini Asso engines of 440 horsepower. The end of the line for the series arrived in 1937, just prior to the Italian commitment to World War 2 (1939-1945).
Beyond the standard fighter versions listed, the CR.1 appeared in several "one-off" prototypes. The CR.2 trialled the British Armstrong Siddeley "Lynx" radial engine while the CR.5 was fitted with the Alfa Romeo "Jupiter" radial and Lamblin radiator set. The CR.10 carried a Fiat A.20 V12 water-cooled unit of 410 horsepower with Lamblin radiator set. The CR.10 "Idro" was a converted floatplane form of the CR.10.
The CR.20 became a related, modernized version of the CR.1, completed with all-metal construction but retaining a biplane wing arrangement. The wings were now of typical sesquiplane arrangement with the upper assembly of wider span than the lower. The CR.20 of 1926 marked a considerable improvement over the line of 1924 and saw better export numbers with a larger stable of global operators.
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