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Its origins can be traced back to 1938 when the Royal Bulgarian Air Force (RBAF) issued a specification for a light divisional reconnaissance aircraft with some ground attack capabilities, built around the Alfa-Romeo 126 R.C.34 radial engine, rated at 770 hp of power for take off. Kaproni-Bulgarski, led by engineer Carlo Caligaris, presented a project for a biplane, the KB-11, which was rejected as the RBAF considered the type as obsolete. Therefore, Caligaris and his team presented a second project, this time a high-wing monoplane with a fixed landing gear. A scale model of this second design was tested at a wind tunnel in Milan (Italy), where Caproni's headquarters were located and after some satisfactory results, a first prototype was built.
This first prototype, nicknamed as "Quasimodo", after the hunchback of Notre-Dame, was flight-tested during April 1940 by Col. Vasil Valkov and Lt.Col.Eng. Petko Popganchev who considered the type as unstable, nose-heavy in level flight and unsafe during forced landings, so the RBAF couldn't accept the KB-11 due to its many flaws.
This left Kaproni-Bulgarski in a difficult situation, as their rival company, DAR, was pushing forward with the better-looking DAR-10A. So, fearing that DAR would win the contract, they hastily redesigned the KB-11 with a high-wing supported by V-shaped struts, a revised undercarriage, a new glazed cockpit, equipped with photo-hatches, walkie-talkies and aerial cameras, and was powered by the same Alfa-Romeo engine the prototype was powered with. This redesign, was accepted by the RBAF and the aircraft was put into green light for mass production under the denomination of KB-11A. Initial operational flights made in early 1941, found that the Fazan was seriously underpowered so a new, more powerful engine was needed.
Before the outbreak of World War 2, Bulgaria signed a contract with Poland for license production of the PZL.37 bomber, so a number of Polish-built Bristol Pegasus XX engines were supplied. However, the German invasion thwarted this operation and the engines were stored. They were found to be very handy for the KB-11A and so the PZL Pegasus were fitted to the 2nd and 3rd batches, which were characterized for driving a two-bladed propeller.
Both KB-11 and KB-11A were armed with two 7,92 mm M-30 machine guns placed in the forward part of the fuselage plus two twin 7.7 mm FK-33 defensive machine guns placed at the observer's post. At the central part of the lower fuselage, the Fazan had also provision for eight 50 Kg (110 lb) bombs or four 100 Kg (220 lb) bombs.
The KB-11 was initially intended to replace both the Czechoslovak Letov S.328 and the Polish PZL.43 in the short-range reconnaissance squadrons of the RBAF. The KB-11A saw action for the first time in joint Bulgarian-German-Italian anti-partisan operations against Tito's partisans in Serbia during 1943, as a ground attack aircraft. Following Bulgarian armistice in 1944 and their switching of sides, the Fazan was used to support Bulgarian ground troops in Macedonia and Serbia, serving mostly with 333rd and 453rd close recon squadrons. However, due to the resemblance of the type with the German Henschel Hs.126 recon aircraft (which also harassed positions of the Bulgarian Army), the KB-11A was sometimes victim of friendly fire who miss-identified the Fazan. That's why the KB-11A's usage during this later-period of the war was very limited and was eventually withdrawn from active combat duty.
After the war, in 1947, Bulgaria transferred many of their former aircraft to Yugoslavia as war reparations, among them 30 KB-11A, which were used as liaison, target tug and trainer aircraft, having their wooden wings replaced with metal ones by Ikarus allowing the KB-11A to remain in active service with Yugoslavia until 1958, although some sources claim it was until 1956.
1st https://en.wikipedia.org/wiki/Kaproni_Bulgarski_KB-11_Fazan
2nd http://www.airwar.ru/enc/spyww2/kb11.html (translated)
3rd https://www.valka.cz/BGR-SFKB-KB-11-Fazan-t57179
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