The Avia B.35 (RLM designation Av-35) was a fighter aircraft built in Czechoslovakia shortly before World War II.
It was designed to meet a 1935 requirement by the Czechoslovakian Air Force for a replacement for their B-534 fighter biplanes.
The B.35 was an elegant, low-wing monoplane with an elliptical wing.
The fuselage was constructed from welded steel tube, covered in metal ahead of and including the cockpit and fabric aft of the cockpit, while the wing was of entirely wooden construction.
Rather anachronistically, the Air Force specified a fixed tailwheel undercarriage for the aircraft, in the hope that this would speed development, as the mechanism for retracting the undercarriage was not yet available.
The first prototype, the B-35/1, displayed excellent flying characteristics and high speed and was originally powered by a Hispano-Suiza 12Ydrs piston engine.
The power plant was later changed to a 12Ycrs with an identical power output, but with provision for an auto cannon to be fitted between the cylinder banks to fire through the propeller hub.
Testing continued until 22 November 1938, when the aircraft was destroyed in a crash that killed the Military Technical and Aeronautical Institute test pilot Arnošt Kavalec.
Nevertheless, a second prototype, B-35/2, was already reaching completion, and was fitted with redesigned ailerons and flaps.
It first flew on 30 December with testing beginning in earnest in February 1939.
A preproduction series of ten aircraft was ordered, but before these could be built, Czechoslovakia was occupied by Germany in March 1939.
Development however was resumed under German control, with the substantially revised B.35/3 flying in August 1939.
The elliptical leading edges of the wings had been replaced with straight ones, and an outward-retracting main undercarriage was fitted.