Bolkhovitinov S

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S
Type	Bomber
Manufacturer
Designed by	Viktor Bolkhovitinov
Maiden flight	29 January 1940
Status	Cancelled
Primary user	Soviet Air Forces
Number built	2

The Bolkhovitinov S was a Soviet bomber aircraft prototype of the 1940s, designed by Viktor Bolkhovitinov. The plane had no official designation, most commonly it is known as "S", which is sometimes developed as Spartak (Spartacus), Sparka (for paired engines) or Skorost ("speed"). There exist also designations for this plane: BBS, BB (Bolkhovitinov's Bomber), LB-S or SSS.

The plane was conceived as a fast light bomber and reconnaissance plane. To obtain high speed and good aerodynamics, it was powered by two inline engines in a fuselage nose, one after another, driving two Contra-rotating propellers. The design had quite unusual look, with long fuselage nose and a crew cab moved rearwards, towards double tailfin. Wings had a fighter-like form and their span was rather short.

The first prototype S-1 was built in 1939, but it was made in order to evaluate an airframe only and was powered by only one engine M-103. It was unarmed and fitted with a fixed skid landing gear. It first flew on January 29, 1940. A maximum speed was 400 km/h.

The second prototype S-2 was powered by two engines and was armed with a single machinegun and bombs. Four 100 kg bombs were carried vertically in a bay between pilot and a rear gunner-navigator, under a common canopy. Its tests started from March 20, 1940. A maximum speed reached was 570 km/h. The plane had good handling, except for take-off and landing, which were difficult due to high wing loading. Its range and speed were also lower, than estimated. As a result, it was decided to improve the plane further. However, the plane was not developed in a favour of next Bolkhovitinov designs, that eventually were not built.

It was first planned to build also an attack plane with 2 Ultra-ShKAS machineguns with extremely high rate of fire, in a rear part of fuselge, firing downwards and manned by a second crew member. Also an interceptor aircraft was proposed, armed with 37 mm recoilless rifle, firing upwards, at an angle and manned by two crewmen.