Avia B.35 Fighter Prototype
Three prototypes of the Czech Avia B.35 fighter were all that existed by the time of World War 2.
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Prior to World War 2 (1939-1945) the nation of Czechoslovakia maintained a strong local military industry that included design, development and production of various small arms, armored vehicles of aircraft. In the years leading up to the grand war, it invested in a low-wing monoplane of modern design by Avia designated as the "B-35". The aircraft was born from a 1935 Ministry of National Defence requirement calling for a single-seat fighter with enclosed cockpit, monoplane wings and metal skin. The product was intended to succeed the aging line of biplanes still in service with the Czech Air Force.
The B.35 first took to the air on September 28th, 1938. The design showcased a slim fuselage with mid-set cockpit, forward-mounted engine and conventional tail unit using a small-area vertical fin and low-mounted horizontal planes. The wing mainplanes were set ahead of midships and given an elliptical shape akin to that as seen in the classic British Supermarine Spitfire. A Hispano-Suiza 12Ydrs 12-cylinder supercharged, liquid-cooled inline engine of 860 horsepower was fitted to the nose section and this drove a two-bladed propeller. The undercarriage, of a typical "tail-dragger" arrangement, was fixed in place and spatted. The wing mainplanes were constructed largely of wood while the fuselage used a mix of metal and canvas with an underlying structure of steel tubing.
In practice, the B-35 seemed a winner for its handling characteristics were deemed good and its performance strong against contemporaries. Maximum speed could reach near 310 miles per hour with ranges out to 310 miles. Rate-of-climb was listed at 2,560 feet per minute.
The program delivered three total prototypes in all and these as the B-35/1, B-35/2 and B-35/3. During testing, the original 12Ydrs engine was superseded by the 12Ycrs series which allowed for a single 20mm cannon to be fitted firing through the propeller hub. The first prototype crashed on November 21st which spurred construction of the slightly revised (smaller ailerons, extended flaps and increased fuselage cross-section) second prototype (B-35/2) - this model took to the air on December 30th, 1938. Following the promising results, the Czech government commissioned for ten preproduction aircraft - though this was derailed with the German occupation of Czechoslovakia during March of 1939.
Despite the occupation, the B-35 product managed to continue development which led to the third prototype (B-35/3), this model earning its wings during a first flight on June 26th, 1939. By this time, the wing mainplanes were modified to feature straight edges along the leading lines (the wings losing their elliptical shape) and a retractable undercarriage was finally fitted. The complete armament suite was now made up of a hub-mounted 20mm autocannon and 2 x 7.92mm wing-mounted machine guns.
In the end, it was these three prototypes that stood for the Avia B-35 aircraft initiative for attention was soon moved to a more evolved form as the "B-135". Bulgarian Air Force pilots were able to trial the B-35/2 prototype back in November of 1939 and later got their hands on the B-35/3 prototype. With the blessings of Berlin, the Bulgarians commissioned for twelve of the type and these served solely with the Bulgarian Air Force during the war.